The Crab Nebula, Revisited
Several months back I picked up an interesting imaging package: The SBIG STL11002M, LRGBHa filters, the AO-L Adaptive Optics, MOAG and Remote Head. Aside from the learning curve for the new software control package (CCDSoft, which is awesomesauce), I had an issue which unfortunately required a repair. And, like any good Law of Murphy, receiving the working camera also means a prolonged spell of bad weather.
I ran a few star tests, played around with things and finally came around to settling on M1. Nearly one year ago I did some work on imaging the Crab Nebula with both my refractor and reflector, so this seemed like a natural candidate to try with another scope and another camera for comparison’s sake. It’s also been a year — an I’ve learned a lot of new processing tricks! This includes some neat actions for Photoshop including RC Astro’s Gradient Xterminator and Annie’s Astro Actions. Then there is also the issue of the imaging chip on the STL11k’s enormous size, vignetting, keeping it mounted flat, preventing it from falling out (which is almost did once!), building a dark library, dealing with the different filters and figuring out how to get it all to work together.
So, this is my first [successful] LRGB image — a previous try resulted in horrible matching of the different colors. I’m sure these will get easier to process in the future, but I must say that I have a whole new appreciation for some of these images people put together! This is built from 5×5 min luminance exposures and then 5×2 min RGB exposures, binned 2×2. In fact, the L and R came from one night and then two nights later I picked up the G and B. So calibration was also a little bit trickier since the background, focus and orientation were all shifted between. I’m sure the color is ‘not right’, but it looks pretty enough to me, especially when compared with my previous attempts. Well, enough babble, here it is — what do you think?
EDIT Dec 26, 2011: I have taken additional frames of just Hydrogen-Alpha with a totally different scope — the NP 101is. What follows is a merge of LRGB+Ha from two different scopes on two different nights. To help balance out the scale difference between the two focal lengths (2000mm vs 540mm), I shrunk it down a bit. This process was simplified a bit through the align (but not combine!) in Nebulosity.