Quote:
Originally Posted by gregbradley
Also I never mentioned anything about self guiding. But now you bring it up I think it is overplayed as a marketing point for SBIG.
I get far better autoguiding results using a separate guide scope and an ST402ME than I ever did with self gudiing using the tiny and extremely noisy ST237 chip. It picks up the edge of the FOV of the scope where most optics are weakest, is very noisy and has a very small FOV. Also blue filter often requires longer exposure times which for my setup meant less optimum where 1 second guide exposures have almost uniformly given the best result.
Also with Ha, S11 or O111 self guiding is virtually useless as often unless the object is super bright it requires something like 30 second guide exposures to register a guide star.
Also the way the camera ceases to autoguide when it is downloading an image and in the case of the STL that is something like 26 seconds means tracking errors are building up requiring time for the autoguider to catch up. I see this problem is addressed with the latest STX cameras which do not interrupt the guider when downloading. If you don't program in a delay between exposures you will get eggy stars from the initial errors having built up.
So if you are imaging LRG and no blue or Ha O111 or S11 there is no problem! As well as using a scope with lovely pinpoint stars right to the very outermost edge of the FOV where the pickoff prism collects the guide star. Having said that self guiding is still handy, especially with long exposures, but a guide scope and guide camera are really too easy to use to argue against them.
So self guiding is a bit ho hum. QSI with their offaxis guider built in before the filter would be way superior. If you get flexure you'd be way better off to use an off axis guider than self guiding.
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Well?....hard to argue with all that Peter, isn't it?
... and this is why so many imagers with selfguiding cameras are forced to purchase a guide camera and guide scope anyway.
Mike