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1ponders -
There's quite a bit to describe, but I'll try for a quick overview and see if it's the sort of info you're after.
To get high quality raw frames needs a scope that's tracking as close to perfect as you can get. I spend about 30 minutes on polar alignment, to the point that Jupiter will stay on the CCD for an hour or so if I wander inside to get a coffee or some sleep :-) It's important because a moving object will contribute to blur at the relatively long exposure times we are all using (I was using 40ms for these frames).
I wait until just before starting to image to check and adjust collimation, so that everything is cold and in its final position. The screws on my scope have been replaced with with hex key headed bolts, so I can use an allen key to adjust everything. It's easier to make fine adjustments that way. I make sure the scope is pointing roughly where it will be used when I set the collimation, cause I know that the collimation won't stay put if I swing from one part of the sky to the other.
I have a homemade 10" f/6 newtonian. The glass mirror was made by Mark Suchting in Sydney. He is well regarded for good quality mirrors and makes quite a lot of large (20+ inch) mirrors.
The tube was made by Gary Mitchell in Sydney out of 1mm thick aluminium. Aluminium is a good material for telescopes because the metal follows air temperature closely, so it won't contibute to tube currents caused by a tube thats too hot or cold.
To get the mirror down to ambient air temperature I use a home made cooling system with a pair of thermoelectric coolers - peltiers. When they are running the mirror can cool by 4 or 5 degrees per hour, much faster than if I just let it cool normally. I make sure that this is switched off about an hour before I start imaging to let the whole mirror stabilise.
The filters I use are Astronomik brand RGBI. They have nice sharp bandpass graphs, so they complement each other nicely. I have been told (don't know if its true or not) that the normal colour filters like the ones you mentioned are not really that good for imaging, but they're ok for visual use.
I have a set of meade colour filters too, but I havent tried using them with the camera.
I captured 700 frames in each of RGB because, at 25fps, that was about how long I had before Jupiters rotation started to spoil the image alignment on its disc. I spent about 1.5 minutes grabbing these frames.
Each colour comes to focus at a slightly different point, probably because of the barlow. I have a motorised focusser (JMI DX1M) which can reset its position individually for each filter and that proved invaluable to getting sharp images in each colour.
I wanted to get a smooth result, so rather than stacking together 700 images and then applying unsharp masks etc I decided to process individual batches of 100, fix each of them up with registax, wavelet filtering, unsharp masks etc, and combine the final 7 in each colour to get a smooth result.
There was a lot of guesswork in this - it's the first time I've tried a batch technique like that, and the 21 runs through registax took most of the morning to do...
Each batch was processed through in Registax, with some wavelet filtering. The image was saved and loaded into Astra Image and sharpened further with lucy-richardon deconvolution and a gentle unsharp mask.
In the end, 7 masters are combined to give the final image for each colour, and then these 3 are recombined to create a colour result. Because I had the images already in Astra Image it was easiest to do it there, but you could probably use Photoshop or some other program.
regards, Bird
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