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First Year of Serious Astrophotography

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First Year of Serious Astrophotography
April 2007

It was one year ago that I received my SBIG ST-10XE + CFW-8a + AO-7 after finding a good deal on a used one on Astromart. My telescope was a CGE1100XLT, which is a Celestron CGE mount and Celestron 11” SCT with XLT coatings. I had been attempting unguided DSO astrophotography for about a year using a Canon D60 DSLR so I was not a complete newbie, just a beginner. The D60 had two major limitations; it was unguided and it had a large amount of noise. I had dreamed of owning an SBIG camera because it had neither of those limitations. It was with high hopes that I began my first year into serious AP.

Of course the first thing you must do when getting a new camera is shooting all those objects that you are dying to photograph; the Horsehead, M51, M13, and a plethora of others. Forget about really learning how to operate the system to its fullest capability. Just learn enough to make it work and start shooting. I think that every budding astrophotographer needs to get that out of their system if only to see why you should spend some time learning the basics. The key is to not spend too much time doing it before getting serious about learning the basics. Unfortunately it took me about 8 months to get serious because I was able to improve quickly enough that I didn’t see I was nowhere near the capabilities of my imaging system.

The first wonderful piece of advice I got (and ignored of course) was to not use the AO-7 and simply use the camera and guider directly into the CGE. But I thought, “My CGE needs the AO-7 to get good tracking” and used it right from the beginning. The trouble was for the first few months my tracking was 50/50. Some nights it worked flawlessly and other nights it couldn’t keep the guidestar for more that a few minutes. Then I found and read Mike Dodd’s excellent article that explained auto-guiding in detail, located on the Yahoo Group “CGE-Uncensored”. From then on I had no issues with guiding and it worked flawlessly every time. One major issue solved but the AO-7 still was having a detrimental impact on my images but I didn’t know it yet.

The focusing is normally another difficult issue to deal with but I already had a head start. Focusing the Canon D60 was a major pain using the SCT focus knob and camera finder. To improve focus I bought a Robo-Focus for the SCT knob and got “DSLR focus” program to automate the focusing routine. With CCDSoft and the ST-10 I was able to measure the quality of focus and I was able to achieve very good focus in about 10 minutes. I cannot imagine doing it by hand, even with a Crayford focuser, so it is the first upgrade I would recommend. I tried Hartmann masks and other focusing aids but the computer got better focus without help.

Around September came another partial revelation. I spent August and September and 10+ nights working on NGC7331 trying to get a really good image. Even better, it was the CCD Image challenge of the month in September so I had a good head start. My image was the best I had created so far and I was quite happy. Then someone entered the contest using effectively identical equipment and totally blew my image away. I knew that it wasn’t simply the processing. Clearly he had gotten much better original frames than I, but how? At this point I hardly imaged for the next few months due to frustration, weather, and waiting for the AP1200 that had been ordered in August to show up for Christmas.

The biggest revelation came in December, a whole 8 months after starting this endeavor. In one of the CN threads a link was given to Richard Bennion’s presentation at an imaging conference. I watched the 45 minute video and all was revealed. I learned that my collimation wasn’t good enough, my star distortion was an issue, my focus wasn’t quite good enough, and how important all of these pieces are to the final image. I removed the AO-7 to improve the overall image quality because the focus point with it was near the extreme back and without it was much closer to the middle. I spent days playing around with collimation trying to judge exactly why my stars were slightly oval and got them spot-on circular with the brightest point at the center pixel. I was finally able to get FocusMax to work extremely well and understood what HFD means and what my typical HFD values should be on good nights and bad nights.

Over January and February I spent every decent night out in the driveway practicing and tweaking each of these parameters. I was also learning how to setup and polar align the new AP1200 mount each time, every time, without fail or undo effort. I was determined not to travel anywhere until I had the basics down. The quality of my astrophotos went way up to the point where I think that I am getting about 80-90% of all I can out of the imaging rig as far as raw frames go. You would think I bought a whole new imaging system. My processing skills still need work and that will probably be the focus of the second year.

The big payoff came on the Messier marathon weekend of March 16th and 17th. My family and I were going to go to a MM star party at a dark site east of Columbus, GA on Saturday for visual work but I went down Friday night to get set up and possibly do some imaging. I had been saving my 3rd attempt at M51 for this dark site as my first two were sub-par. Eventually the wind died down somewhat Friday night and I let the system shoot 10 minute subs in LRGB while I went to bed in the tent. The results were more than I was hoping for given the conditions. See the pictures at the end to follow my progress.

After a year of experience on this learning curve, here are my suggestions to budding astrophotographers who are just starting out in the field of serious AP.

  1. If you have a decent mount like the G11 / CGE or maybe even the ASGT or LXD-750, get a quality advanced amateur camera first. I would rather have my SBIG ST10 on the CGE than a DSI on the AP1200. Some may disagree with that sentiment but I really think the SBIG or your favorite equivalent camera makes a bigger difference than upgrading from the entry level mounts to the top tier.
  2. The second upgrade is the mount and the last thing to “upgrade” is the scope. You may have different focal length scopes for different FOV but that isn’t really an upgrade. Almost any scope can be used to produce wonderful images as long as the target is appropriate.
  3. Read Mike Dodd’s paper on guiding and watch Richard Bennion’s presentation on getting good raw frames many times. That information is vital to improving the quality of the images and can save you months of experimenting to come to the same conclusions.
  4. Practice, practice, practice. Don’t worry about heading for a dark site until you can reliably setup and polar align, guide well every time, check and fix collimation, and focus very well. After 8 months I learned that spending two months practicing and not trying to take images for show was the best thing I could do. I still took images during the practice sessions but the goal was to test if the setup was correct, look for errors, and understand and improve the behavior of the system. Polar alignment, guiding, and focusing can be done any mostly clear night and lunar phase isn’t important. Focus on the details and the imaging part will take care of itself.
  5. Learn the ins and outs of your imaging rig, which goes along with #4. Learn how faint a guide star you can use or how bright. How long can your guide exposures be and still get good guiding? How accurate does your polar alignment need to be before it doesn’t seem to matter? How accurate is your GOTO and when it wasn’t performing like normal what did you have to do to fix it? The more you know about the capabilities of the system, the better your decisions will be out in the field when choosing targets or recovering from a bad start and the less time will be wasted. Better to “waste” nights at the beginning in the comfort of your own driveway testing the extremes of performance than out in the middle of nowhere after driving for an hour.
  6. Dedication is the key to success. There have been nights where I simply wasn’t going to go outside because I was too tired, it was too cold, or I just wasn’t in the mood. Every time that happens it is a missed opportunity to learn and improve something and depending on where you live, you may not get many opportunities a month. There has to be a balance but watch out when it starts becoming really easy to find a reason not to spend some time outside. Once I really understood collimation, guiding, focusing, and polar alignment, it usually took about 5 nights for each skill to really learn it well enough. Some nights I could work on more than one skill but that was usually after the 3rd night of practice on the first one. At this point I have the confidence that I can be up and imaging at my best within 90 minutes unless a total disaster happens. I also have the confidence that I can let my mount go unattended for the rest of the night and stop it in the morning but that is mostly a function of the mount. With that confidence I don’t worry about spending four hours setting up and imaging with nothing to show for it. I am free to choose the nights I image and let others go since I am very likely to have a successful session, sans weather. I don’t have to image every good night hoping that some of them will come out well like I did before.
  7. Image processing. A 16-bit camera really needs a photo editor that can work with 16-bit images (48-bit RBG) to process them well. The only one I know of is Photoshop CS and CS2 but I think there are some others now and it makes a very big difference. You need to work with the full dynamic range to get the best results. When you start getting really good raw data, it is not unreasonable to plan to spend around $1000 for a set of image processing software and books if you do not already have it. Yes it is yet more money to spend but worth it.

I hope other beginners find this recount of my first year useful and helps them avoid some of the mistakes I made. Following are some pictures of M51 throughout the year as I improved my skill.

File written by Adobe Photoshop® 4.0
1st attempt at M51 April 2006, C11 + Focal Reducer + AO7 + ST-10XE + CGE mount

2nd attempt at M51 December 2006, C11 + Focal Reducer + ST-10XE + AP1200 mount

3rd attempt at M51 March 2007, C11 + Focal Reducer + ST-10XE + AP1200 mount at a dark site, 10 minute sub-exposures.

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