Alan Brock
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Thanks to everyone for the kind words; really encouraging!
@Jim - Thanks for the feedback! It's definitely something I will look at this closely in the future as I've yet to find a satisfactory method of web sharpening. Unfortunately, the softness in this image is not (at least completely) a result of resizing. In order to keep background noise to a minimum I had to balance finding an acceptable level of sharpness and noise control. At some point I need to reprocess it and/or shoot it with a newer camera.
rhee wrote:
YEY!! This is what I have been waiting to see!!! Thanks Alan.
You've got to illustrate/explain 'how' in great detail!
I am all excited!
Kee
Alright Kee, here is an in-depth look at capturing an astrophoto. Fair warning...LOTS of boring stuff written below! Also, I don't mean to seem like I'm talking down to anyone. Since I don't know anyone's experience with this, I'm just going to go through it assuming there is no previous experience with astronomy.
First, the gear. I've included a cell phone pic of my setup at the end. The mount is by far the most important piece of equipment. It HAS to be stable and able to track the night sky smoothly. Also, for imaging, you should never weigh it down anywhere close to its carrying capacity. I use a Celestron CGEM which is really good for imaging with small scopes. Speaking of telescopes, there are two involved: an imaging scope and a guide scope. For an imaging scope (black one in the pic below), I use an 80mm f/6.25 refractor. This may seem slow, but it's actually really fast in the world of telescopes. It's relatively small; only slightly longer than a 70-200 w/lens hood attached and much lighter. Next is the guide scope. As you are setting up the mount, it has to be aligned VERY precisely with the celestial north pole/north star through a process called polar alignment. This way the rotation of the mount can cancel out the earth's rotation through the night. However, in spite of precise alignment, there can still be movement based on slight imperfections in the gearing of your mount, slight gust of wind, etc. Since we're imaging in minutes/hours, even movement of a few pixels can ruin an image. Therefore, we use a guide scope. A small camera is attached to this scope and locks onto a single star. If it detects any movement in that star, it sends a signal to your mount so it can compensate for this movement and keep your image stable.
Next is image capture. There are far more advanced cameras out there, but for simplicity I use a DSLR. You can have them modified specifically for astrophotography, but I've found no need to do that. I use a stock camera and attach a light pollution filter. This picks up plenty of detail for me. When capturing the image, you takes lots of sub-exposures of your target. Mine have ranged anywhere from 15 seconds to 8 minutes each. The reason for this is noise control. You're using a high ISO and will be pushing the image a lot in pp. Therefore, since noise is random, you take a lot of subs and stack them together in post. Then software will remove the noise in the image while keeping stars and other detail intact. It is also necessary to take several sets of callibration images. I take darks and flats. First the darks. Because imaging is in minutes at high ISO, there will inevitably be several "hot" pixels...completely red, blue, or green pixels with no data. Taking completely black images will identify these pixels so they can be subtracted in post. Finally, you've got flats. Telescopes inherently have curvature and vignetting, most pronounced at the edges. Taking pics of a completely flat, evenly illuminated surface again lets software calibrate and correct these imperfections (as well as dust spots).
Finally, there is image processing. I use a free program called Deep Sky Stacker to stack all of my images together and get a final stacked/calibrated image. It then goes to photoshop where you can spend hours teasing out the little bits of detail while keeping noise in check. This was the steepest learning curve for me and there is no part of it that is similar to "normal" image editing. I use the tutorials by Jerry Lodriguss and his astropix.com website as my Bible.
Some final notes. There is no type of photography that is more frustrating than astrophotography. There is so much that can go wrong, it's cold, and you're often fighting exhaustion. That being said, there is no feeling in photography like when a nebula pops up on the camera screen after a successful 8 minute sub-exposure! Also, find the darkest sky possible, including no moon. I've got everything set up to run off a deep cycle marine battery so I can hit the road to a dark sky site in the mountains. So, if you're still reading...God bless you! Happy hunting and clear skies!
Astrophotography Setup
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