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Yes that guy is hardcore. 49 hours exposure - wow.
I saw the name Roger Clark and I know he does a lot of DSLR testing and reports on their performance. I also read some of it and they were talking about the histogram which is more of a DSLR imaging technique.
I agree you can take some great images with a DSLR. Its just harder work on the dim objects and the difficult part with a DSLR is to maintain star colours. They often wash out to white in DSLR images. Even those you linked the star colours are off.
The basic theory is the signal has to get above the noise floor of the camera system to see anything. My point really is with a CCD camera with deep wells and low read noise that is rarely less than 15 minutes.
If the top guys are seeing a gain with 30 minute subs using these types of cameras given stable weather and good tracking its worth a try to see for yourself.
I think also it depends on the target object. Some are quite bright and require a different strategy. I wouldn't do 30 minute subs on the Orion Nebula for example, it would be a mess but on a faint spiral galaxy at a dark site with excellent tracking and a deep well camera I would.
This is all highly theoretical anyway because I imagine very few would be able to achieve round stars in 30 minute subs anyway. That's a whole long runway up to achieve that. Its gonna require a very good mount that works reliably, perfect polar alignment like only achieved with T-point modelling, a very good PEC (a whole world in itself), really well balanced, a good autoguiding system with no flexure so that means self guiding or an off axis guider or an AO unit ( it also means guide scopes are unlikely to be able to achieve it), no cable drag, a solid pier or tripod that is well supported and a reliable power supply. If you setup every night it would be a no go. If you have a permanent mount but not all the bells and whistles needed to set it up its a no go. Unless you have a very expensive mount it is probably unrealistic.
Accurate tracking is a large enough barrier to make greater than 10 minutes unreachable for most. It really is the big obstacle in astroimaging. 10 minutes is hard enough most of the time!
Greg.
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