Quote:
Originally Posted by dulwich.hill
So why do I need to guide using a DSLR?
...thinking music....
Ah, I think I understand...guiding is required because DLSRs take a single long exposure shot. Whereas CCD can take many frames per second the so that an image stacker software package can remove any image position errors.
If I used a single shot DSLR, what length exposure do I need to take an nice shot of Saturn? Do I really need a guider ? Is a single long exposure shot better than a stacked frames image? Or is this a purists argument (sorry I don't want to start a flame war!!!).
So, why not buy a cheaper and lighter CCD?
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there are CCDs and CCDs
for planets you use a webcam or more sophisticated versions like the DMK/DBK and more exotic and expensive offerings that take a large number of images at very short exposures
for deep space you use a CCD-much much more expensive-that are cooled, very sensitive and can go for hourlong exposure or more if you are so inclined-usually people go for 5 to 30 minutes
so for deep space to get these long exposures you need to autoguide-even with the best mount in the world
you dont need to guide for planetary-and sun and moon-work
you also dont need to guide if you go for relatively short exposures of deep space targets-say 20 or 30 seconds and stack heaps (think 50 or 100 or more) of frames
a zillion 1/25 second frames of deep sapce objects wont unfortunately give you the same result as a single long exposure-you just are not capturing enough signal
PS all this is at prime focus
with a DSLR-as I have said earlier you can shoot both . An all rounder may not be as good as some specially designed fit for purpose camera but doesn't lock you in to one specific type of imaging either-and you can always use it for populating facebook if you decide at some stage to go down a particular path
hope this answers your questions