Hey guys.
On my to-do list i've said i'll write a how-to guide for astrophotography with a dob. Including afocal digicam stuff, as well as webcam astrophotography.
I haven't started on it yet, but Nortilus, ballaratdragons etc have started on the afocal route, and so would hopefully benefit from some of my experiences.. Also a response I wrote to a new webcam dob imager on CN had a lot of the hints + tips I would probably put in my how-to guide..
So here's part of my response to him.. it's not strictly just for webcam imaging with a dob, there's some points in there that may also be relevant for afocal digicam stuff.. anyway i'll post it here and it might make a start to my guide anyway.
Hopefully someone gets something out of it.
Quote:
Things to think about in the next couple of months as you keep trying things out:
1. Make yourself a hartman mask to aid in focusing. Focus on a star first, and once the 3 images overlap each other, then swing to the moon/planet and focus should be spot on.
2. Get a better focuser, or re-lube your existing one. I found that trying to focus with my old rack & pinion was very hard as the image drifted through the FOV in 13 seconds. Every time you moved the knob, the image wobbled around and it took a second or 2 to dampen down to actually check the focus. I've now got a moonlite CR2, and the slow-mo focus knob is perfect for getting crisp focus. The image doesn't wobble about when i'm focusing as it drifts through the FOV.
3. Get or make an illuminated finder. After staring at a laptop screen, trying to re-align looking through your finder is very difficult, as the black crosshairs don't stand out against the sky. Now the red background stands out against the sky and it's very easy to re-align the planet in the finder so that it will drift through the FOV. Once I align the finder at the start of an imaging session (where I know where to position it so the planet will drift through), I only waste 5-10 seconds between captures realigning.
4. Ensure your az motion is as smooth as you can get it. It makes realigning easier if it's not stopping and starting and jumping about when you're trying to move it short distances. Perhaps try one of the base mods i've done.
5. For the moon, capture in black&white. You don't need colour. Use a shutter speed of 1/500 or even shorter on bright areas of the moon. Your shot above is terribly overexposed in the lower left corner. Less (zero) gain and a faster shutter speed will help with this. When you can see detail on the preview screen (and it's not washed out), that's when it's time to start capturing.
6. Start without a barlow until you get prime focus right. The image scale won't be as big, but you need to get the technique right before you make it harder for yourself as the image moves too fast out of the FOV, so it makes it hard to check and set focus, hard to check and set colour settings, hard to check and gain/shutter speed.
7. Check your collimation. Newtonians will produce bad images if your collimation is not good. De-focus on a star and check that the shadow of the secondary is in the centre of the disc. Collimation needs to be good for visual observing too, you'll just get bad views all the time until you're comfortable and confident checking and setting your collimation. It's the must-know skill to learn if you own a newtonian.
8. If the seeing is really bad, don't frustrate yourself by even trying to image. It's ok when you're learning, because any practise is good practise, but as you get better, you'll want to go forwards, not backwards. Most times it's not worth trying to image something low on the horizon either.
9. It takes time, and practise, and patience. Imaging with a dob is not easy, and a lot of the time it's not fun, and a lot of the time you don't get results worth posting.
But persevere, and you will get there. I've only been doing it for a few months, and my images have slowly improved..
Here's my first Jupiter (Dec 22nd):
and here's my latest (Feb 24):
My first Saturn was just like yours.. a white oval blob. 
Keep at it, you'll get there. Let me know if you have any questions, i'm happy to help.
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