Astronomy has been something I've always been fascinated by and why not combine our gear love (in this case a stock Canon EOS 7D) and love of the stars with photography? Astrophotography can be amazingly beautiful as you can see from the images below submitted to planet5D by Alan Brock.
I had seen Alan's photo of the Orion Nebula on Gizmodo and decided to investigate further. Turns out he'd posted a whole bunch of info over on the FredMiranda forum so I contacted him to see if I could share his amazing talents with the planet5D family.
Orion Nebula Astrophotography
From Alan Brock:
I took 102 images at 2 minutes each for the nebula and 40 images at 15 seconds long for the bright core. Camera was a stock 7D with a light pollution filter, and the scope was an Orion 80mm EON f/5.25 refractor. My mount was an autoguided CGEM; I've done 8 minute long exposure before, but had to limit this one to 2 minutes sub-exposures because it was taken in my light polluted back yard. I took an equal number of flat and dark calibration frames. Everything was stacked in Deep Sky Stacker and then edited in Photoshop. While I'm at it (and since I had trouble posting multiple images earlier), below is another one. Nearly the same setup, except I used a 40D and 7 minute sub-exposures for just under 3 hours.
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!
Have you given HLVG plug-in a try?
The green is probably from the LP filter. I always use a custom WB off of a gray card with it, but somehow the green still shows through I guess. I had not actually heard of the HLVG plug-in; I will definitely give that a try. I've never been thrilled with the core of my M31 image. I should've taken shorter subs and blended them; IIRC, it took quite a bit of PS shenanigans to get the core as it is now. Color isn't right still, but upon saving, PS froze and deleted ALL of my layers! I have not had the desire to go back and reprocess. Good to see others interested in AP; I look forward to seeing your work!
Light Pollution Filter: What does it do? Would this help to subdue the city light for a regular night photography?
A light pollution filter is a mandatory piece of equipment IMO…even if you are shooting from a dark sky site. I use an Astronomik CLS filter that clips into my camera; it's removable so it doesn't affect normal imaging at all. It blocks out certain wavelengths of light, such as those in street lamps. If you are shooting in an area of high light pollution or light from the moon is making the sky bright, it allows you to still photograph your target without the sky washing out too much. It also makes your camera more sensitive to wavelengths of light found in certain nebulae, such as the red areas in M42 above.
Aside from camera gear how much money is involved in such an elaborate set up?
As far as budget goes, the sky is the limit. (Pun?) Astrophotography gets VERY expensive. Also, it depends on what type of imaging you want to do as the gear requirements vary greatly (widefield/Milky Way, planetary, or deep sky imaging). I tailored my gear to do deep sky imaging (nebula, galaxies, etc) and, IMO, it is the minimum setup for this type of imaging. I don't think any of it is considered cheap in terms of price or build quality, but I do think it's the least expensive setup that will still get good images. With that in mind, let's start with the mount. For a smooth tracking, solid mount, budget around $1500 minimum. Don't skimp here! For the imaging scope, a good entry scope is an 80mm doublet or triplet refractor; plan on around $900 for this. This will be plenty of scope to keep you busy on targets for years. You've got to have an autoguiding setup; buy one from Orion for $400 and enjoy the simplicity. Then there are tons of accessories that I consider absolutely necessary: mounting rings, dew control, portable power source, filter, optical field flattener, remote camera shutter. Plan on another $1200ish for these. You've also got to have a camera and laptop, but most everyone has those already.
So don't let the total number intimidate you, because it's a lot! I built my setup over a span of three years. I made a list of everything I needed and then bought a piece at a time. I remember it used to drive my wife crazy! She'd get me something off the list for Christmas, I opened it, and then stashed it in a closet not to be used for a few more years! But I researched what I needed, I had a goal, and slowly worked toward it; it's not like my intended subjects were going anywhere! Good luck with everything.
P.S. To get an idea of how astronomical (I'll stop now, I promise) the prices can get, Google Astrophysics Telescopes and look at the “Prices” tab…
[Click to see Full Image]
[source: Alan Brock on fredMiranda All images and text used with Alan's permission]
(cover photo credit: photo from Alan Brock)