C, C and D

It all started with the hot pixels. The Mallincam video camera that I had bought provided wondrous views of the skies above, but these views were always accompanied by a collection of colorful extras: pixels activated by the heat of the camera would glow red, green or blue next to the object that I was looking at. I would try to ignore them, but they sat there staring me in the face.

M82 was still a sight to behold:

But I constantly thought "there must be something I can do about this noise."

First, where does the noise come from? To know this you have to know a bit about how CCD cameras work. A CCD is an integrated circuit that is made up of an array of "wells." Each of these wells makes a single photo-sensitive site. The hardware takes advantage of an effect from quantum physics called the photoelectric effect. In the late 1800s Heinrich Hertz observed that if you shine a light on some materials, they will give off electricity. CCDs use this effect to turn photon hits into electric charge. Conceptually, as light hits the chip electrons collect at the bottom of the wells. When the exposure is done, the charge at each site is read off one by one and turned into a small binary value. This collection of binary values can then be made into an image.

In the Mallincam the digital image is turned into an analog video signal by hardware in the camera itself. This signal goes over a composite or S-video cable to your computer where you turn it back into digital video with a capture card. All of this saves you the bother of processing the digital image yourself. But, it also prevents you from processing the digital image itself.

The reason you might want to process the digital image yourself is to manage noise. In a perfect world, the only thing making electrons at the bottom of those wells would be actual photons from the heavens. In addition, a perfect world would have circuits that can read the charge perfectly and without any error. Of course, this perfect world does not exist. All sorts of factors conspire to put false data into our digital images and this false data is what we call "noise."

If you spend any time at all looking at Mallincam pictures you can see a lot of different kinds of noise. There are the hot pixels which are caused by heat and dark current (see below). There is the greenish amp glow in the corner from the video amplifier. There is noise caused by the conversion to and from analog video. Finally, if you aren't careful, there is electrical noise caused by your power supply transmitting RF into the video cables.

The noise that I'm interested in tonight is called "dark current." Dark current is extra electrical noise created by the sensor hardware itself. This causes electrons to collect in wells even though no photons were captured. If the dark current is strong enough the pixel will register as having data when in fact it captured none. So you get false, or "hot" pixels.

The amount of dark current that you see depends on the temperature of the sensor. So, the first thing fancy CCD cameras do to combat dark current is to use sophisticated cooling hardware to make the chip as cold as possible.

The second thing you can do to manage dark current noise is to take dark frames. Here you cover the CCD and shoot a picture with exactly the same exposure time and at the same temperature as you used for the picture you took. Then, you take the resulting data and subtract it from the data for the actual exposure (also called the "light" frame). If you are lucky, this will exactly cancel out any false data in the light frame.

This is what I wanted to do with my Mallincam pictures. But I couldn't. With the Mallincam you can't actually capture the light frame and dark frame data. All you can do is grab an image file that has bits in it that are the result of image processing in the camera, then a digital to analog conversion and then an analog to digital conversion. All of this processing destroys the integrity of the signal and makes it impossible to do dark subtraction. At least in my experience.

So I went out and got a small CCD camera to play with. I picked a Starlight Xpress SXV-M7 monochrome camera. Why?

1. It's about the same size and weight as the Mallincam, so I'm used to handling it.

2. It uses a similar sensor to the Mallincam, except that it's black and white only. These Sony sensors are pretty sensitive and low noise.

3. I got black and white so I would not have to worry about color. Color in the Mallincam was always the best and worst thing about it. Plus, it was galaxy season anyway.

I found the SX camera pretty much as easy to use as the Mallincam. The nicest thing was that I only needed a single USB cable to run the whole thing. The most complicated thingwas that I had to learn how to process the digital data myself. We'll get into that next time. But after a bit of practice, I did finally manage to get rid of those hot pixels:

It turns out that a few months with this camera taught that there is a lot more to noise in CCD imaging than I had considered at first. Next time we'll see that to a first approximation processing astronomical pictures is just one huge exercise in hiding the noise so that you can exaggerate the signal.

Mount Lessons

I've had my Astro-Physics Mach1GTO equatorial mount for about two months now. The mount has continued to perform better than I could have expected, and I expected a lot. So while it may seem like I have already gushed uncontrollably about it I have just a few more things to say before I just go back to happily using the thing.

Setup and Alignment

I have my setup routine pretty much down. Even though it takes more trips, it's actually faster than setting up the CG-5 for use with the camera. For visual use it would only be a bit slower. Here is what I do:

1. Put the portable pier down on my patio. I have a fixed spot for it.

2. Roll the mount out in its rolling box. Put it in the pier. Attach the three knobs that hold the mount on the pier.

3. Attach the counterweight shaft and the two weights.

4. Go in the house and get the telescope. Put it in the saddle.

5. Balance the telescope. I found this tricky at first because the axis bearings on the Mach1 are pretty stiff. You can't really balance the telescope by finding the point at which the telescope does not move when you undo the clutches. The axis tension tends to hold it in place. Instead you need to find the point where the motion along the axis is most smooth and uniform. It takes a bit of practice.

6. Set the mount in the "Park 1" position, where the RA axis is horizontal and the DEC axis has the telescope pointing north. The telescope tube and the counterweight shaft should be level.

7. Use the polar scope to align the mount on Polaris.

8. Plug everything in, Resume from Park 1 on the hand controller.

9. Now I run one pass of the "quick drift" polar alignment scheme which is outlined in this pdf file. While the description in the documentation is somewhat involved, the scheme is actually very simple and mostly involves pointing the telescope at two stars that you can pick. I'll provide details in a later section.

10. Now hook up the camera and laptop. Find a star near where you want to look at things. Point the mount there. Center it in the camera view. Focus. Hit "recalibrate" on the hand pad. Done.

Here is what I like about this setup routine:

1. I only need two stars (the two used for polar alignment). It's easy to find two stars to use. It could sometimes be a pain to find six for the Celestron.

2. No complicated and fragile pointing model. The multi-point pointing models that the Celestron and Meade mounts use are all derived from the software used to make the alt-az fork mounts point and track objects for visual observation. To "align" these mounts you point them at various stars and the computer builds a little model to translate celestial coordinate to alt-az and the poor user does not have to mess about with "complications" like polar alignment. This is great but also annoying in some ways. If for whatever reason you accidentally shifted the telescope after building the model, your only real hope is to rebuild the model from scratch. With the Celestron GEM mounts this manifests itself as needing to redo pointing alignment after you have used the pointing model to find tune polar alignment. Which is unfortunate.

Here is my epiphany about alignment: if your equatorial mount is well built and precise, the only alignment you need to do is polar alignment. The Astro-Physics literature actually says this, but I did not believe it. I was wrong.

The various multi-star alignment routines that have been built to make life "easier" for users has actually worked to hide this fundamental fact from them and thus made the world ultimately more confusing. The latest high end mount from Meade (the LX-800) takes this even further. Check out this thread about it to see what I mean. In addition to multi-star "alignment" you now also have to deal with guider setup and plate solving before you can look at things in your telescope. Is this really easier to use?

Stability and Consistency

In the last six weeks I've continued to make progress on my projects to make rudimentary video images of all the Messier and Herschel 400 objects. This has gone very well, and I've added images of a few dozen new objects to my little collection. Two nights of this work stand out. They might be the same night, but since I do not keep good notes, I have forgotten. On April 18th I captured what was for me a record number of images in a relatively short amount of time. You can see all 29 of them here. Being able to work that fast with the mount and the camera brings up the intriguing possibility of doing an entire Messier Marathon with the camera. But I'm not really interested in that. Anyway, the consistency of the mount allows you do work this way. Once aligned and calibrated the mount just never seems to go "off". Object after object can hit the small chip of the video camera.

In addition, the mount seems impervious to wind. Wind is the enemy of stability and good tracking, yet one of the best nights I had in the last six weeks was on a night where the gusts were up to 20-25mph in my back yard. Remarkable.

Meridian Games

The meridian is a something that hangs over every German equatorial mount. In this design the telescope sits on top of the declination axis and is counterweighted on the other side. Here is a poor schematic:

In this design the telescope and the counterweights are always on opposite sides of the pier. When the mount is properly aligned, the RA axis will point straight north, which means the pier will be right on top of an imaginary line that runs North/South right down the middle of the sky which we call the meridian. Another bad picture:

The issue with German mounts is that as you track closer to the meridian you can end up in one of two bad situations:

1. The weights or scope can hit the pier.

2. The weights can end up above the scope, which is bad for balance.

So avoid these things, the controller forces you to follow some rules. The main rule is that if the scope is pointing East its body should be on the West side of the mount and vice versa. This keeps things from hitting the pier and keeps the weights below the scope.

Which brings us back to the meridian. What the above rule means is that if we want to go from looking at things in the East to looking at things in the West we need to flip the scope over the mount so it's on the opposite side:

This is a rather drastic and potentially destructive move. Things in your telescope can get out of alignment. You can catch wires on knobs. And, it can throw off your pointing. So, users of German mounts tend to try and avoid flipping at all costs. But, this is annoying since the exact time when you want to look at most objects is when they cross the meridian, because that’s when they are highest.

The Mach1 mount does a few things to make this better. First, the geometry of the mount allows it to track far past the meridian if you want it to. So you can pick up an object on the East side and follow it across its highest position in the sky without needing to flip anything around. Second, the build quality of the mount assures that when you do flip over, all you need to do to restore good pointing is to calibrate with the position of one bright star on the new side. I ended up always needing to do this with the Celestron mount anyway, even with all the fancy alignment software.

Finally, the control software in the mount allows you to shift where the mount thinks the meridian is, and thus delay or force flips when you want to. So, if you want to pick up an object that is 30min East of the meridian and track it until it is low in the West without flipping, you can tell the mount that the meridian is actually one hour further East than it really is. It will then dutifully flip the scope over as if the object is already in the West and then track it for hours without flipping. Just make sure nothing hits the tripod when you start this maneuver. If you are really a mount dork, you can read more about this here or in the AP documentation at their web site.

Astro-Physics even has a clever scheme that uses flips to make sure your polar axis is aligned. This is the basis of the "quick drift" alignment scheme I mentioned before. Here is how it works. First, set up a finder scope on your main telescope that has a crosshair that you can rotate so that one direction corresponds to East/West and the other to North/South. Orion makes a good one that can do this.

Now, pick a star near the meridian and near zenith and have the mount point your finder scope at it. Center the star and hit "recalibrate". Now shift the meridian either East or West by one hour depending on which side of the meridian you are on to make the mount flip over. If you are well aligned, the star will still be centered in the finder. Any shift East/West is the finder scope not being quite aligned with the mount. Any shift North/South is the mount not being quite aligned in altitude. Use the altitude adjustment to get rid of half the North/South error. Use the adjustment on your finder scope to get rid of half of the East/West error. Use the keypad to center the star the rest of the way. Flip the mount again. Iterate this process until the star stays centered.

Now pick a second star that is at also near the meridian and at least 30 degrees away of the first star. Point the telescope there. If you are polar aligned, the star will again be centered in your finder. Any shift is a result of azimuth error, so with the azimuth adjuster to remove it. Now point back at the zenith star. If it is off center, center it with the keypad, hit recalibrate, and slew back to the second star. Adjust the azimuth again. Repeat this until the star stays centered as you slew back and forth. You are done.

There are a few things to like about this scheme:

1. It's easy. In particular, once the finder scope is set up well it usually only takes one or two iterations to get aligned.

2. It's stateless. You can redo the procedure any time you want without worrying about confusing any software. All you are doing is adjusting the mount's geometry relative to the sky. The control software is not keeping any sort of score.

3. It uses a nice ergonomic finder on top of the telescope. No fussing with polar scopes that are hard to look through. I use the polar scope to get a rough alignment, but always do this scheme for finer adjustments.

Small Details

Finally, here are some small things that make the mount a pleasure to use.

1. The cables are great. The power cable has a locking mechanism so it won't work its way loose without you knowing it. The motor and keypad cables are all these cool XLR connectors like for pro audio equipment. It all just works.

2. I like the LED keypad display. It works better than the LCDs I've used before.

3. The documentation and support are great.

There isn't too much more to say. If you are in the market for a really really good telescope mount and you have the funds, I can't imagine doing better than the Astro-Physics product. It is a well-built no nonsense straightforward piece of equipment that just works and is gloriously free of useless bells and whistles. It's a reminder that it's still possible to achieve great things by building in small numbers and paying careful attention to detail.

Value for Money

I’m about a year into using my astronomical video camera to view deep-sky objects from the city and capture small and simple pictures of what I see. All things considered the experience has been tremendous, but there was an obvious weak link: the mount that I bought does not track well.

This is not to say that the mount did not perform up to my expectations. In fact, given the relatively small amount of money that I paid the mount has been excellent. Good telescope mounts are hard to build well, and even harder to build cheaply.

That said, you can do better, and about six months in I decided that I would be doing this enough to consider how to do better. After my first investigations, I wrote this about the relationship between cost and quality in a mount:

In general you will find that in terms of mechanics you get what you pay for. There is a direct and linear relationship between how much money you spend and how well the mount will hold weight and smoothly track the sky with the least amount of fuss. When you spend more money you get more reliable machinery that is built to a higher standard of precision. Those gears in the motor drive will be asymptotically closer theoretical perfection. More importantly, by building in small numbers the premium manufacturers can maintain a tight hold on testing and quality control.

What this means to me is that you should start cheap, decide if you are serious, and if you are serious then go and buy your last mount ever. Mounts are like tripods in photography. If you are really serious about photography it’s well known that you will eventually spend $1500 on a carbon fiber tripod and a really good ballhead. The only question is whether you spend $3000 on inferior tripods before finally upgrading to the one you should have bought anyway.

Having started cheap and decided I was serious, the only question now was: which mount is the last one I want to buy. The choices before me were:

1. A more expensive Chinese mount. Here you have the CGEM from Celestron, and the various Synta mounts like the Orion Atlas. All of these have the same basic mechanics and manufacturing quality as the CG-5 that I had bought, but are built larger and heavier so they are more stable. I could not find a convincing case that the performance of this hardware is consistently good enough that I would not want to throw it away in a year. The Atlas and the CGEM also weigh almost 40 pounds. More on this later. iOptron in Taiwan also makes a mount in this class, but which is lighter.

2. Losmandy G-11. By all accounts this is an excellent piece of hardware. Unfortunately they’ve been in a two year death-march updating their control software, which does not fill me with confidence. The G-11 is also relatively large and heavy given the load that it can carry. Finally, there is a lot of Internet literature on do it yourself tweaks to this mount, which brings it down in my mind. But I’m not really being fair.

3. Takahashi EM-11 or EM-200. Here we are finally getting into the “just works and works forever” category. Beautiful fit and finish. Apparently great mechanics. Best polar alignment scheme in the business (more on this later). But, it requires a laptop for doing automatic pointing. And, the main documentation on the entire mount is a 10 page pamphlet poorly translated from Japanese into English. You can also only get service on this mount from a single company that is far away from me.

4. Astro-Physics Mach1. You saw this coming. Since this is the one I picked, I will now ramble on about it at length.

My pre-purchase justification for going with the Mach1 was as follows:

1. Weighs 30% less than the Chinese mounts but carries at least twice the weight.

2. Weighs about the same as the EM-200 but is more stable.

3. Extensive and competently produced documentation and support materials available on their web site.

4. Extensive and competently produced software support on the PC side if I want to go that way.

5. A few clever control features in the mount itself (more on this later).

6. Nearly 100% positive evaluation of the mount on the Internets.

7. Excellent Internet support. The owner of the company can be found doing remote diagnosis of issues on the mailing list. Impressive.

My main pre-purchase worries about the mount were:

1. Complicated to set up and polar align compared to the Tak, where you just point the polar scope and go.

2. Expensive.

3. Maybe a bit too large. The EM-11 is more my size, and would retain my “bring the mount and tripod out in one step” workflow.

4. Expensive.

Still, I had nothing to lose by putting my name on the waiting list (Astro-Physics makes two production runs of the Mach1 per year, one in the spring and one in the fall. So you put your name on a list and wait until the next run) while I deliberated further. By the time my name came up on the list six months later I had decided that $6000 on a mount is expensive, but not as expensive as spending $4000 now and then $6000 later when the first one didn’t work. Two weeks later four large boxes appeared at my house.

Here is what you can say about Astro-Physics, their excellent product photography does not do their products justice. At this point I should include a picture of the mount head, or the polar alignment adjuster knobs, or the keypad, or the wires that go from the control box to the motors or even the knobs that hold everything together. But, I lack the talent and technical ability to create an adequate picture. Every one of these items is built and finished to a degree of polish that I can only describe as good enough to make Apple jealous. I spent five minutes just turning the knobs on the Vixen style saddle. I had never seen machined knobs that were that good. Not even on my Really-Right-Stuff ballheads which until now were my standard for gratuitously expensive pieces of machined aluminum.

I spent the first night with the hardware just putting it together. There were lots of parts and knobs and whatnot. By the time I had it set up it was time to go to bed, even though the sky was clear. This is a hard situation to be in.

Happily over the next two weeks we had enough good weather in Pittsburgh for me to get the mount set up at night. Some impressions from the first setup:

1. Polar alignment was not bad. The polar scope is easy to use, and the clever “quick star drift” scheme outlined in the documentation works well. You can get set up in about 15 or 20min, which is the same time it used to take me with the CG-5′s computer. The adjustment knobs on the mount for altitude and azimuth are incredible. This is still more complicated than the Takahashi mounts with their superbly integrated polar scopes. On those you run a computer program that tells you where in the polar finder to put polaris and you just do it. You are done in five minutes.

2. The mechanics of the mount, in use, are practically perfect and absolutely predictable. With good polar alignment you can calibrate on a single star and afterwards every single GOTO goes exactly where you want. The CG-5′s alignment scheme, while clever, was never consistent. Some nights pointing would be perfect and other nights it would drift around unpredictably. You also have to memorize where six or seven bright stars are in your sky on any given night to make it work. The Mach1 only needs you to find one star.

3. When moving the mount with the keypad there is no apparent backlash in any direction. This is unlike the CG-5 where at slow speeds you’d have to wait a second or two for the gears to wind up before the mount would move.

4. The mount remembers the date and time. Hallelujah.

5. My one and only gripe so far: the clutch knobs can be hard to use because they are so close to the motor boxes. Oh, and the portable pier/tripod is not the easiest thing to fold up or adjust. That’s all I can think of.

I also got to set up with my camera. Here’s a single shot to give you an idea of how well the mount performed:

This is NGC2903 and the picture is a stack of 12 frames shot at 2 minutes exposure for each frame. The telescope was being used at 1000mm focal length. Every one of the 12 frames was perfect enough to use. The object barely moved on the screen after each exposure.

Just last month I shot this object with the old mount using my small refractor at around a 300mm focal length:

This is a stack of 1 minute frames at less than half the focal length as I used above. And the tracking is visibly worse.

“But you should be using a guider” you might say. And you’d be right. I should be using a guider to smooth out the raw tracking error in any mount. But guiders are notoriously finicky devices, and their ease of use, or lack thereof, is pretty much linearly related to the underlying performance of the mount they are guiding. So the way I see it, I’ve finally bought a mount that will be worth guiding, because the guiding will just work.

In my mind, this gets to the core value of this product. This is a product that defines the phrase “just works.” The behavior and performance of the mount is absolutely predictable. And the value of that is hard to measure.

“Value” is one of those buzz-words that makes the rounds of business meetings and marketing materials. I think in most cases it refers to something that a company would like you do believe you are buying, but in general it’s not the case. Most of the time when you spend more money you have just spent more money. It’s not often that you spend more money for something and when that something arrives you can stare at it and see the exact linear relationship between the money that you have spent and the value that you have gained. All I can say about the Astro-Physics Mach1 is that you can see every penny of it. It cost ten times more, and really is ten times better than the cheap mount that it replaced. You can’t say that about too many other products.

Grab and Go

One key to enjoying the telescope hobby is to know how to set up and tear down your equipment quickly. This is especially true around Pittsburgh where the weather can change instantly from perfect to disastrous. Over the past couple of months I have developed a reasonably systematic routine in the deployment of the telescope. With it I can set up my full video rig with automatic pointing and tracking in about 20 minutes. While not instantaneous, this is pretty quick, and I would say that it approaches what reasonable people can call “grab and go.” The following is my reference checklist and there is no reason in the world for anyone else to read it except to be bored. But I already wrote it down, so I might as well post it. These setup instructions will work for any of the Celestron equatorial mounts. They can work for other mounts too, but a lot of the details will be different.

1. Put the mount outside. I have a spot on the patio behind my house that I use every night. This patio spot gives me a good view of most of the sky to the west and south and a reasonably good view of the north and east. The house and trees behind the house block the lower parts of the eastern sky. A large tree in the yard blocks the northwest. Otherwise things work pretty well.

2. Point the mount roughly north. If it’s already pretty dark, use the hole in the polar axis of the mount to sight Polaris, which sits right over the roof of the house.

3. Set up the Telescope. Go and get the telescope and put it on the mount. Also fetch all the accessories you’ll be using. I use my scope in two general configurations. For visual work I use a 1 1/4″ diagonal and various Televue eyepieces. For video work I use my Mallincam with a light pollution filter and focal reducer on it. In addition I’ve been using the Celestron F6.3 focal reducer on the back of the scope lately. So I attach that as well. The camera goes straight into the telescope without a diagonal. This is more convenient. I attach it with a Televue 2 inch visual back because I had the camera fall out of the crappy Celestron visual back with the tiny little useless hateful set screws. The set screws failed to hold the camera, and it just fell out of the tube an on to my concrete patio. This sucked. The Televue is a 2 inch tube that holds the camera solidly using a compression ring. Highly recommended.

So my setup goes: telescope, F6.3 reducer, 2 inch visual back, a 2 inch to 1 1/4 inch adapter tube, then the camera.

4. Balance the telescope. This takes two steps. Set the mount up so that the right ascension axis is horizontal. Now you release the clutches on the declination axis of the mount. This is the one that points north and south and runs parallel to the axis of the telescope. Then while holding the scope, put it in various positions. Let go slooooowly and make sure that the scope mostly stays in place. I try to balance the scope when it is horizontal and when it is mostly vertical. Tracking and pointing near the zenith is a lot better if you get this right.

5. Now balance on the right ascension axis. This is the one that is orthogonal to the body of the telescope. This is easier. You want to position the weights on the counterweight shaft so that when you release the RA clutch and let go of the telescope (slooooooowly) the scope does not move. This is the simplest mechanical task that there is in astronomy, as far as I can tell.

Some people tell you to purposely set the balance to be a bit heavy on the east side of the mount because it smooths out the behavior of the tracking motors. Depending on what part of the sky you are looking at this means either you want the either the scope side or the counterweight side to be heavier. I have never had any luck trying to do this because it means you need to shift the counterweights whenever the mount flips, and I hate touching the mount in any way after I am done aligning it. Maybe you’ll have better luck with this.

6. Put the scope in its “home” position. For my mount this is the one where the counterweights point straight down and the scope points straight north. Peer into the finder scope and look for Polaris. It should be at least in the field of view. When the scope is in this position I turn the video camera so that later on I know which way north and east will be oriented in the field of view. This turns out to be handy later.

7. Power. Now go get your power supply. I had been using a big 12V battery, but it started to fail recently, so I bought a couple of 12V power supplies that I can plug into an outlet on the outside of my house. This has proven to be more reliable the last few times out.

8. Now wire everything up for video. The camera gets a control cable, an s-video cable and 12V power. The control and video cables go back into the house through a sliding door. The video cable goes into the USB capture widget and the into the laptop. The control cable ends at the big Mallincam control box. The largest box ever built for holding five buttons and a knob.

Then I plug the telescope controller into a 25 foot cable and run the other end out to the mount. Finally, a second 12V power cable goes into the mount itself.

9. Initialize the Mount. Work your way through the Celestron setup menu. Enter the time and date and then tell it you want to do a “two-star” alignment. This alignment will let the hand controller learn how to point at things in your sky. What you will do is pick two stars on one side of the meridian (either the eastern part of the sky or the west) and then 3 or 4 stars on the other side. I tend to start in the west and then move to the east because I tend to be impatient to go and look at things that are still rising. The eastern sky is also somewhat darker than the south and west, since the PIttsburgh light dome is primarily to the west and south of me.

For most of the summer the first star that I’d pick was Arcturus. The scope will attempt to point at the star, but it will usually miss. If the scope were already perfectly polar aligned and set up in exactly the same place as the last time I was on the patio, it might hit perfectly. But, these things are never true. So, it will miss by a bit. Use the arrow keys on the hand controller to point the scope and get the star in your favorite sort of finder. I use a 9×50 optical finder, because I’ve never figured out those red dot things. YMMV.

10. Focus. The start should now be in the field of the camera. If it is not, then that means your finder scope and telescope are not aligned. If that’s the case, remove the camera and put an eyepiece into the telescope to fix that. Assuming it is, I then go inside and fire up the video capture software. If I have not disturbed the focus too much, the star will be in the video feed and mostly in focus. Still, it’s best to go and get your Bahtinov mask to make sure.

The Bahtinov Mask is an insanely clever device that creates a diffraction pattern on bright stars that will tell you exactly when you have them in focus. Just follow the instructions and you can’t miss. After I’m done I remove the make and put on the dew shield. I’ve gotten away with just using a shield, for now. If I were smarter I’d use those heated strips as well but it’s only been an issue twice in a year.

11. Star Align. Having focussed the telescope we’re ready to finish the star align. First grab the camera controller and turn on the cross-hairs. Making the cross-hairs is a bit of a chore that is too complex to describe here. Maybe I’ll make a separate page about that. With the cross-hairs set up, use the mount controller to center the star. It will look like this when you are done:

In this picture the horizontal lines point roughly east/west and the vertical lines indicate north/south. The actual directions might be reversed, but the important thing is that I’ve oriented the camera so that the arrow keys on the controller are predictable. This is a small touch that makes life easier later.

Anyway, when you have centered the star hit “Align” on the hand controller to tell it that you want to go to the next star. The hand controller will suggest another star in the western sky. You can use the menu keys to pick one that you can see that are not too close to the horizon. Center it in the finder then in the video camera, then hit Align.

11. Calibration Stars. Calibration stars refine the pointing model of the mount to compensate for its mechanical limitations. The hand controller will ask if you want to add “calibration” stars. Hit Enter to say yes and it will suggest a star in the east to use for further alignment. Pick a star that is well placed and hit Enter. The mount will then flip around and try and point there. As before, it will miss by a bit. Center and align the first star, and the hand controller will ask you about another calibration star. Hit enter to say yes and repeat. As you add more stars you’ll notice that the pointing will get more and more accurate. Usually the third and fourth stars will be in the field of the view of the camera. If this does not happen, you probably missed with one of the previous stars which means you should just start over.

12. If you have to start over, don’t be frustrated. This happens from time to time especially as the sky changes and you need to pick different stars for alignment because the ones you were using before have moved to the wrong side of the sky or behind a tree. Don’t panic. Just unplug the mount and do the whole routine again. Pretty soon you’ll end up with a new set of stars that you can use for a month or so and everything will run smoothly again.

13. Notes on Pointing. At this point, let’s review. We’ve set up the mount and we’ve told it to point at six points in the sky. Each time we’ve corrected pointing errors by hand, allowing the computer in the hand controller to build a pretty detailed model for how to point at things. My experience is that this pointing model works very well, especially if you avoid meridian flips. This is why I try to stay in the eastern part of the sky after doing all of this. If I cross back over to the west, the mount has to flip over, and this invites the creation of pointing errors. I’ve had it work pretty well, and I’ve also had results that were so bad that I unplugged the mount and started over. In one worst case, I had to wipe reset the firmware in the hand controller after some bug corrupted it. But, these are outliers. In general things work very well at this point and the total time I’ve spent from putting the mount on the patio to having good pointing is about 10 minutes. But, for video good pointing is only half the battle. In order for the mount to track over even short time exposures, we have to make sure the polar alignment is good. Luckily, this is not hard.

13. Polar Alignment. The Celestron hand controller has a wonderful piece of software in it that allows you to use the pointing model that you just worked so hard to build to polar align the mount. First, tell the hand controller to point the telescope at a star that is near the meridian and also near the “celestial equator”. All this means is that the star should not be too far north or too close to zenith. The hand controller will complain if you pick a bad star, so study your planetarium program to find a good one. I used Altair for most of the summer, and have recently switched to Enif in Pegasus after Altair wandered to the western sky. Remember, I try to stay on the eastern side of the meridian for all of this.

Now go into the Align menu and pick Polar Align and then Align mount. Hit Enter and the scope will point back to the star you just picked again. Repeat the center/align dance on the video screen. You’ll get another message from the hand controller about starting the All Star Polar alignment. Hit enter to start. The scope will now point to a different spot in the sky. This is where it thinks the star would be if you were polar aligned. At this point you put the controller down and you use the altitude and azimuth knobs on the mount to re-center the star in the field of view your finder scope and then the camera. When you are done, hit enter. Then find Undo Sync in the Align menu and hit enter on that too.

14. Polar Alignment Notes. There are a few things to keep in mind with this Polar Alignment scheme. First, you always want to end your alignment by moving the altitude of the mount up. You want to do this because the knob in the back that changes the altitude gets tighter when you push the mount up, which means it will stay in place better when you are done. I loosen the knob at the start end give the mount a shove downward so I know I’ll have room to move up later.

Second, it’s really handy to have a remote version of the video feed near the mount while you are playing with the knobs. I use VNC on my iPhone so I can see my laptop screen without needing to run back to the laptop. It’s also handy to use this trick when focussing.

Finally, the Undo Sync is important. The first part of the Polar Align routine “syncs” the mount to the star you picked. This messes up the pointing model to make pointing near the star accurate. But, as you move away from the star the mount points less and less well. Also, if you move the mount a large distance while finishing the alignment you may find that your pointing gets way off. In that case, unplug the mount and redo the star align. In my experience this hardly ever happens. The one time thought I needed to do it, my pointing didn’t really get any better and then it turned out that a cable snag was the reason the mount was pointing half a degree too far south all the time.

15. Final Notes. I’ve just described my setup process in about two thousand words. But you should not be discouraged by this. With practice I can do all of this setup in about 20 minutes. While this seems like a lot of up front work, remember that the guy that just goes in the house and grabs his manual alt-az on a tripod will then probably spend 5 minutes star hopping to each dim deep sky object that he wants to look at. Meanwhile, when this process works well, you can spend the next three or four or five hours with objects that are invisible in the eyepiece hitting the tiny chip in that video camera dead center every time.

Using this setup routine I’ve been able to get the Celestron CG-5 mount to do the two basic things you need an compuerized equatorial mount to do:

1. Point at things accurately.

2. Track objects in the sky for time exposures.

I use two telescopes on the mount, an 8 inch Celestron SCT and a new 85mm Televue refractor. I run the 8 inch scope at a focal length of between 1000mm (F5) and about 700mm (F3.5). On the best nights, the mount will point this scope so that every object I ask for is just about dead center on the Mallincam’s small chip. This means that we are hitting a field of view that is at most half a degree wide and about 22 arc minutes tall every time. That’s similar to the field you would get using a 100x eyepiece, which is pretty good.

The refractor has a native focal length of 600mm and I can also run it with a focal reducer and extension tube to get to about a 400mm focal length. This gives me slightly more than a degree of field of view so I can fit bigger things, like

or

or

The main complaint I have about this mount is that it does not track smoothly. I’ll sometimes get 4 frames in a row at one or more minutes that are perfectly sharp and then right after that I’ll get 4 frames in row where the object jumps 3 or 4 pixels to the east or west. I could try using a guider to clean this up, but I get the feeling that the guider will not be able to deal with these large jumps over relatively short exposures.

In the future I plan to spend a ludicrous amount of money on a mount that will track much more smoothly. But I predict that when I do so I’ll miss the relative sophistication of the Celestron software. Being able to use the video camera in the main telescope to do polar alignment can’t be beat. Hopefully the other guys will decide to try and catch up.

At this point I am morally obligated to end this post with yet another picture of M27. So here you go.

Clear skies to you all.

Deep Sky Projects

Astronomy is an endeavor that is full of catalogs. And I don’t mean the ones that are on the Internet that are designed to separate you from your hard earned cash. For much of its history, astronomers did little else than catalog what was in the sky. Before the telescope, this meant just what you could see with your eyeballs: the brighter stars, the planets, the moon, sun, and their various activities and relationships. With the advent of the telescope, more larger and more elaborate lists of esoteric objects could be created. The most famous of these was the one created by the French astronomer Charles Messier.

Messier was a comet hunter by trade, but he is much more famous for his catalog of interesting “deep sky” objects. The term “deep sky” in this context generally means non-stellar objects that are now known to be outside the confines of our solar system or, indeed, our galaxy. These objects are “deep” because they tend to be small or faint or both. The idea is that you have to look deep into the sky to detect them. This is not universally true, of course. Many of the brighter Messier objects are easily visible to the naked eye under darker skies and if you know where to look. But the term sticks.

So how did a comet hunter get into the deep sky catalog game? Well, in his scans of the heavens, Messier kept running to objects that looked liked comets in his small telescope (small, fuzzy, non-stellar). However, to his annoyance, the objects did not move with respect to the background stars. This meant that they were something besides the comets that he was interested in. In order to help out his fellow comet hunters he decided to make a catalog of these objects. Over time this list expanded to contain about 100 various nebulae, star clusters, and what we now know to be galaxies outside of our own. Later it was expanded and corrected to contain a final tally of 110 objects. You can look up the list in various places.

The Messier catalog is significant not only because it happens to contain some of the nicest objects that there are to look at in the sky, but also because everyone who becomes interested in deep sky observing eventually needs to find every object on the list. This activity serves as a benchmark of sorts; a common ritual that we can all share.

So of course one of the first things that I did when I broke out my new telescope about a year ago was to start working through the Messier objects that I thought would be practical to see from my yard. It’s good to have a project to work on. Keeps the obsession focussed. I actually did better under the light pollution than I thought I would. All of the showpiece objects were easy to find (M42, M31, M45, etc). I managed to sniff out some dimmer objects and to find hints of low contrast extended star clouds like M33. Still, there were obvious boundaries, especially for objects that sit in the sky glow to the south and west of my house. I never managed to find M74, and have only ever seen the faintest hint of something as bright as the Lagoon Nebula (M8).

When I got the video camera this all changed. Even relatively short time exposures with the CCD puts all of the Messiers well within reach of an observer of modest skill using a modest telescope. To illustrate this for myself, I set out to take “snapshots” of every Messier object as I encountered them with the camera. My goal is to just collect a recognizable rendition of the object that is representative of what you can do with short exposures (a few minutes total) with the Mallincam. I can’t draw, so I think of this as the closest that I will come to sketching what I see like a traditional observer might do. The most esoteric image processing technique that I’ll get into here is stacking multiple short exposures to reduce noise and get a bit of detail enhancement. I’m not going to go out and collect 50 hours of “data.”

Here’s a link to the first 85 images: http://www.flickr.com/photos/79904144@N00/sets/72157627091459246/

There are a few there that I would go back and redo. But for the most part I’m happy with what I have. I’m especially satisfied with the summer stuff. The fact that the camera can reach into the skyglow and get this picture of M8:

or this of the Eagle Nebula (M16):

or this of the Trifid (M20):

never fails to amaze.

The summer Messier objects also brought a few surprises. I had never seen the cluster M11 before, and seeing this in the camera motivated me to get the eyepieces out and take a look too:

I think the one weakness of the video camera is on star clusters. Stars all take on a square-ish pixelly look in video rather than the pinpoint sparkles that appear in the eyepiece. M11 is well worth seeking out and is easy to see.

The globular cluster M22 also surprised me:

I knew all about M13, of course. But the fact that there was this other huge ball of stars in the same sky never occurred to me.

As the summer progressed, it became pretty clear that filling out the last holes in my Messier image catalog would not be difficult. The winter objects that I had missed before would soon come back around and I’d get another shot. So it was time to look further afield for more things to find. Here, another legendary catalog stepped up to provide a longer term project.

In the late 18th and early 19th century the astronomer William Herschel (and his sister Caroline) not only advanced the art of telescope building to various new heights, but also discovered and cataloged an unfathomable number of deep sky objects. Herschel’s list eventually reached some 2500 objects and formed the basis for the modern “New General Catalog”, or NGC for short. In addition, there are two collections of the more notable Herschel objects called the “Herschel 400″ and the “Herschel II” lists which are a good place to start to explore this larger frontier. Over the last year or two the noted Internet Astronomy personality “Uncle Rod” has been working his way through these lists and chronicling his efforts. I figured if he can try for the whole thing, I can try for the brighter stuff from my house. So that’s what I’m doing, starting with the H400 list of the brighter stuff. If nothing else it will answer the question “just how much light pollution is too much for this camera?”

Here’s what I have so far, as far as I know: http://www.flickr.com/photos/79904144@N00/sets/72157627409712613/. Favorite surprises so far?

NGC6946:

The fact that I can see this much of the Veil (NGC6995):

And, the occasional great planetary nebula (NGC6781):

Anyway, as I said before, it’s good to have a project to work on. Keeps the obsession focussed.

I have to end this piece with a shot of M27, The Dumbbell, because it never fails to look good. So here you go.

Tens of Dollars

A guy at the office and I have a running joke about the amateur astronomy business. I will opine that the market is just begging for some great product to solve problem X for every telescope user in the world. And then we both snicker that one could make tens of dollars by building and offering such a product for sale. This is a marketplace where selling thousands of units a year makes you a massive player. It’s a market that is in a permanent niche.

Now, to some people, this is a feature. There is always that class of hobbyist whose idea of sheer hell is that their interest would somehow blossom into something generates a genuine mass market interest. Even back in the 80s there were already people who thought that computers had been dumbed down too much when people started putting them into boxes for you instead of making you build a wire wrap board. These people must be really pissed off now.

Astronomy serves as a case study in what happens when the mass interest never hits. Let us be realistic. This is a hobby that is primarily enjoyed by a few tens of thousands of users almost all of whom are male and aged between around 41 and 67. As a result, the market has the following odd characteristics:

1. The market is small. There will never be a product here that has the psychological impact of something like the iPhone. Or the Apple II for that matter.

2. The market is conservative. These people really hate change. I’ve mentioned this before, but I can’t think of a single consumer device besides a commercial telescope mount that still uses RS-232 for anything. The only other uses I’ve seen are for esoteric industrial control applications. This is also a market that isn’t quite sure that eyepiece designs from the 19th century still don’t have some technical advantages. I could go on and on.

Because the market is small, there are very few players in the market that can scale their operations to modern levels. The largest companies by far are the ones based in China. Orion Telescope and Celestron are the two most well known names here. They both source all of their products from the same large optical company in China. But, as you move up the food chain cost and quality, you move into smaller and smaller companies. The most well respected maker of refractor telescopes and telescope mounts is Astro-Physics. They make at most few dozen instances of each of their products a year. If you are lucky you can get a mount almost immediately (like now) but usually you’ll wait around a year. If you are unlucky and want a telescope be ready to wait 10 years.

Here is another example: there is a guy who used to work for Astro-Physics who now makes what I hear are bitchin’ tripods for the mounts. But the only way you can hear about him is in a forum post, or a classified ad. You can only order one of his tripods via email, and you will have no idea when the thing will actually be delivered.

You see this over and over again. More than half the time you go to any large dealer of astronomical products and look up something you want to buy, the words “pre-order” or “out of stock” or “back ordered” will be right next to the “buy” button. It’s almost easier to just look at the astronomy equivalent of ebay and wait for used stuff to show up. It will often happen faster than the new stuff. This is an infuriating state of affairs. People (by people I mean me) are now programmed to expect to just go to Amazon and buy anything with one click. The astronomy world destroys this expectation completely.

The issue of scale also comes up in the software business. Several of the most used pieces of astronomy software are primarily developed by one person. Not a small team led by one person: one person writing all the code (off the top of my head I can think of Skytools, PHD guiding, Nebulosity, the Astro-Physics mount software, and Equinox). While all of these tools are certainly functional, they will not win any design awards, and they are limited in the rate at which they evolve (c.f. the market is conservative). It’s just now occurring to folks that wireless control of equipment might be neat. Or that user interfaces might want to evolve past the Visual Basic Forms sort of look and feel.

Of course, there is an upside to all of this smallness. If you are lucky you will find small groups of people making just what you want and doing a really good job with customer service. Every single one of these small companies that I have mentioned (except the tripod guy) runs a mailing list on Yahoo where questions are answered by the people who run the company. Not some customer support staffer in India. The actual guy who runs everything. This is pretty neat. It’s too bad that they can’t hook up with that Amazon commerce engine though.

It’s good that you can find good support because you are going to need it. The combination of the small size and conservative nature of the audience means that there are not a boatload of companies breaking down doors to make telescopes and other astronomical equipment easy to use. I don’t think the industry has ever really gotten past assuming everyone buying telescopes has a little DIY streak in them and enjoys constructing custom wiring harnesses by hand, or hacking marine battery packs, or any number of other little construction projects. Let’s just say that product packaging is not necessarily a great concern. For example, you can buy a $10,000 Dobsonian telescope and then find out that you have to wire up the cooling fans to a power supply on your own because it’s too much trouble for the company to do that in its “factory”. In fact, you can go to manufacturer A’s web site and read about how one of their best features is that they don’t make you wire up the fan by hand, like manufacturer B does. It would be comical if it were not so sad.

Although I have learned to adjust to the strange ways of this industry, I still find myself wishing that it would move from the darkness of an obscure DIY niche into the light of a true mass-market retail industry. I’d like for things to be in stock, and I’d like to not have to worry about knowing whether I am using the right god damned power connectors between my battery and my telescope.

Side note: the power connectors on all this equiment are universally awful. It’s pathetic that you can buy an equatorial mount that costs as much as a used car and someone will still tell you that it order to get a clean power connection you might want to “spread the pins” of the power connector just to be sure. I mean come ON people.

I dream of a day when people will realize that spending hours calibrating a CCD camera just isn’t fun, and they should figure out how to automate the process. Or the day when I’ll be able to 1-click purchase a filter with confidence instead of having to call around to fifteen small-time dealers before I find one. But, I think I’ll just have to make the best of the here and now, because I don’t see that day coming. If anything, the industry is shrinking and what we have now may be the best it will ever be. After all, there can’t be that many people waiting in line to make those tens of dollars.

Odds and Back Ends

Back in part 2 I promised a short piece on all the other fussy details related to using the Mallincam. Instead I got into an extended tangent on the subject of telescope mounts, focal length and image scale and various other things. The final missing piece is what you actually do to see the pictures. After some experimentation, I have a scheme I’m comfortable with.

The defining aspect of the Mallincam which makes it different than other astronomical cameras is that its output is an analog video signal. A more traditional CCD or digital camera captures light into the wells of its sensor and then when the exposure is done, the voltages are read out of the sensors wells one at a time and converted into discrete digital values. These are then sent over a wire to a storage card (digital camera) or your computer (CCD). To actually see a picture you have to do some post-processing on the file to convert it into an image format that you can display and then parse with your eyeballs.

The Mallincam is different. There are two outputs on the back of the camera: one for S-video and one for composite video. You hook a regular analog video cable to these ports and then to a monitor and you can look at images directly from the camera. It’s as if you hooked up a camcorder from the 1990s to the back of your telescope. This is a great convenience if you want to just look at the pictures and not bother with any computer-based post-processing. Viewing with an old CRT security monitor gives you images that are as good or in some ways better than you can manage in a computer. The CRT has a luminosity to it that images confined to LCD screens lack. Believe it or not you can still find some CRTs for sale… but there are also people who use small and very expensive professional LCD video monitors.

Me, I use a computer. I actually ran a CRT screen side by side for a couple of nights as well, but didn’t see too much advantage in it. Anyway, I always have my laptop nearby since it’s running my planetarium and observation logging software. So naturally I’d want to use it to capture pictures. This leads to the question of how to capture video frames in the machine. On my Macintosh laptop, I tried two different schemes:

1. Firewire capture device, some Mac software for image adjustment. I bought a relatively expensive Canopus capture device. S-video goes in one side and Firewire goes into the Mac. Very high quality. Sadly, I was never happy with the capture and processing end. There is a tool called Camtwist with a lot of nice features, and even some filters specific to the Mallincam. Unfortunately it the basic tools it has for adjusting contrast, gamma, color and brightness are hard to use and much too fussy. The astronomy filters are pretty cool, especially if you are limited to shorter exposures. But the lack of a good set of basic controls killed this tool for me. The other worry with this tool is that it’s essentially written by two guys who have stopped working on it, so new versions of MacOS are sure to break it.

2. USB capture device under Windows. Again, the device has an S-video (or composite) input and then hooks up to your computer with a USB cable. For very little money you can pick up a “Dazzle” video capture box on Amazon. The quality is not as good as the Canopus, and you need special drivers that may or may not work on your Windows system. I had to buy and install Parallels to make this work. The drivers did not work in VMWare. In a strange bit of turnabout, once you get the device working there is a basic capture program that is much better than the Mac stuff in the “just works” department. I refer to AmCap.

AmCap doesn’t look like much on the outside. It has your basic shitty Windows XP layout and various modal dialog boxes. But, it does a couple of critical things right, which I will now explain. All of the Mac video capture progams assume that your goal is to capture a huge stream into a movie and then import it into Final Cut or iMovie or something. What this ends up meaning is that it’s hard to find software that has the video feed in one window and the adjustments in another window and lets you make adjustments to the video while seeing the feed change in real time. This is exactly what AmCap does.

When you fire it up, the main window has the output from the video feed. You can then open an adjustments dialog and drag it off to the side and push the brightness, contrast, saturation and other knobs around to fix up the picture. The sliders have an effective range of adjustments and a good “scale” in that they don’t change too fast which was my complaint about the Camtwist adjustments.

I should put a screen shot here to show you what I mean, but I don’t have my camera running to do so, so you’ll have to wait for later.

In practice the main adjustments you end up making are brightness and contrast. In a relatively light polluted environment like my back yard, you are always fighting the brightness of the skyglow and trying to beat it down without losing detail in the object that you are looking at. So the scheme is to drive the brightness down as much as you can and push the contrast back up to get some detail back. All the while you want to keep and eye on the noise. In the best cases, you can get good object detail and a nice dark background with acceptable noise, like this:

In the worst cases, I’ll have the brightness slider bottomed out and still have a huge glowing ball of noise in the frame, like in this shot:

I was looking at this object low in a very hazy sky, thus all the awful noise. This is about the best you can do with just AmCap. You could, and people do, use additional devices to adjust the signal before it hits the capture device. The Mallincam has spawned a large amount of interest among telescope geeks in archaic analog video processing devices to try and fight the dual problems of background brightness and noise. The most popular of these are based on old time base correctors that you used to use to copy old VHS tapes. These are hard to find since the main use for them was pirating VHS video tapes that no one cares about anymore. But if you snoop around you can still find them. Rock Mallin used to sell a modified one that he called the “DVE”, but he ran out. You can even find versions of these devices that allow you more sophisticated adjustments in color, brightness and contrast. I have not as yet experimented with anything like this, mostly because of the cost and also because I don’t want to add yet another box to my chain of complexity. But, if I ever run longer exposures that I do now, I’ll look into it more carefully.

AmCap also lets you capture single frames out of the video feed into a bitmap image file that you can then look at later. I’ve gotten into the habit of making a folder for each object that I look at on a given night and capturing 5 or 10 good frames into the folder. “Good” here is defined mostly by the quality of the tracking during the exposure. The mount is not always perfect, alas.

For a while I’d go over my screen shots at the end of the night and pick one that I liked for each object and throw them up on flickr. Here is a favorite object out of the southern summer sky, the Eagle Nebua:

It’s a bit noisy and washed out because it is relatively low in the southern sky. This puts it right in the worst sky glow that I have in my yard. On a bad night you can’t even see many stars with binoculars in that part of the sky, and it’s supposed to be filled with the rich star clouds of the Milky Way.

Anyway, a week or so ago I discovered that if I had five or ten good frames that were fairly well aligned, I could use some code in the Nebulosity application to “stack” the frames together and smooth out the noise and detail. What you do is tell Nebulosity how to align the pictures, and then just tell it to chew on the frames. The result, after a 5 minutes of Curves adjustment in Photoshop, looks like this:

This is really fantastic in my opinion. It’s about ten minutes of work above and beyond staring at the original video and capturing a few good exposures. But the stacking makes a big difference in the final quality of the picture. If you are interested, the tutorial I used to figure out Nebulosity’s stacking feature is here. Skip the parts about pre-processing and go right to the explanation of how to align images and do Standard Deviation stacking. It’s actually possible to do some dark frame subtraction with the Mallincam as well, but if you start down that road pretty soon you’ll find yourself running 8 hours of LRGB data collection when you should sleeping. I’m not sure I want to go there yet.

If you are observing at this point that all of this seems a bit similar to CCD imaging, I don’t think you are off base. There are similarities, but there are also differences. I think the Mallincam still does more pre-processing of the image than even one shot color CCD cameras do. The result is that you can can both observe the object in “real time” and then later post-process the images in a limited way to make them prettier. I like doing both.

That said, it’s not hard to imagine someone building a more streamlined CCD capture application that did some of the work that the Mallincam’s video hardware does. It should not be beyond the realm of possibility to quickly capture data from a short CCD exposure and process it into a color image in real time without all of the baggage of a long winded traditional CCD calibration and image processing workflow. Imagine an iPad app that can talk to one of the new eyepiece-sized CCD guider cameras, capture an image and show it to you instantly while you stand next to the telescope… maybe even over wifi. You could then save the individual files to your computer later to do stacking and other processing. All things being equal I’d buy that app.

To close, here are two more shots from my recent nights out. First, M8, the Lagoon nebula:

This is five stacked frames. Next, M17, the Swan. This is also around five stacked frames.

The best part of summer is coming. Hopefully the skies will be clear enough to see what’s up there.