Quote:
Originally Posted by g__day
I'm learning shot processing now that I have pointing, tracking and focusing going reasonably well. My next purchase is likely to be a reasonable CCD - but how should I plan this move?
Obliviously I can do alot more with the software side of imaging - but just seeing Jase's shots compared to mine shows I have alot to learn. At present I say go to the Helix Nebulae - I lock on and shoot say a 1, 2, 4, 6, 8 and 10 minute series of shots on a C9.25 then start Photoshop CS2 processing (levels and curves and a bit of filtering) - real basic stuff. I'm yet to stack or really play hard with my images.
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Valid questions indeed. You should ask yourself what you're interested in imaging. Wide field, narrow field, conventional RGB, mapped colour (SII,Ha,OIII) narrowband etc etc. If you don't know, do some research. Find out what makes you tick. For me, I enjoy wide field vista as it puts things into perspective. But occasionally I mix it up and image something with a longer focal length. Image processing flow is different depending on what object you're imaging and what you're trying to emphasise in the image i.e spiral structure, dark nebula wisps etc.
A C9.25 is a fine scope for hunting down galaxies due to its long focal length. It has a low magnification secondary which reduces field curvature - a major benefit. A variety of cameras would suit this instrument with exception to large format chips. You can still use them but you'll have problems with vignetting and an chips size will emphasise the field curvature so you'll end up heavily cropping most images.
As I've mentioned in a previous post. Internal guiding has its advantages, but there is nothing stopping you from getting a camera with an imaging chip only. Then continue to guide with an off axis or guidescope with a web cam. Plenty of options available. You need to work out what works for you. Personally, I would recommend getting a camera that does internal guiding - it's then up to you if you want to use the guide chip or not. Of course, SBIG are the only manufacturer that provide an internal guide chip as this design is patented. So this limits your options. What is important is the imaging chip capabilities and whether it meets your imaging goals.
For someone who is just getting their feet wet, go with an ABG chip. Dealing with blooms of an NABG chip can be a pain. Sure, the great QE of an NABG chip is appealing, but if your goal is pretty pictures you can work around this by increasing the sub exposure times with an ABG chip. If you plan on imaging narrow fov's, then a NABG can work well. Stay away from them if you intended to do wide field imaging. You can guarantee that there will be a few bright stars in the FOV that will severely bloom resulting in considerable processing to recover the image. This is a real pain if they cut through nebulosity. You can get trick to dither and subtract the blooms, but when you are just starting off I don't think you'll want such a step learning curve. There is a minor advantage of using a NABG chip with narrowband filters as these filters are typically quite dark i.e. transmission ratings aren't extremely high so the sensitivity/high QE of an NABG chip can reduce your exposure time.
You'll find that most if not all CCD camera's today are USB. You may pick up a seconds parallel version on Astromart or other forums. I'd suggesting going USB. Some manufactures such as SBIG offer parallel to USB upgrades, though these upgrades are typically "return to base" so you need to ship the camera off to the US.
I've highlighted the colour vs. mono (using colour filters) in this thread. I would consider a logical progression for a seasoned DSLR would be a one shot colour CCD. Though everyone is different. Mono with filters will give the what I'd consider the most superior result, but its considerably more work.
Finally (leaving the best last) - image processing. Yes. You need to understand the concepts of image processing and there is really no right or wrong way, providing you're happy with the end result. If you can't image process, then you will not be utilising the full potential of your equipment imaging capabilities. Don't be afraid to push your data hard and experiment with different combining (medium, average, sigma reject/clip etc), stretching (levels, curves, DDP, shadow/highlights etc), layering (both single and grouped) and masks (highlights and noise control etc). There is so much to try such as Ha blending with different data channels to bring out object structure. Experiment, experiment, research and experiment more. Seriously, I spend more time in front of a computer screen processing images than I do at the telescope.
Post your recent images for comment on the DSO forum is a good way to get up to speed in processing. Plenty will offer assistance and tips. Once you're comfortable with the quality of your images, post it on the SBIG yahoo forums where the big players are. I've done it a few times and found it extremely constructive. Good advice and criticism can only bring out the best.
When it comes to image processing - we learn by doing!