Quote:
Originally Posted by riklaunim
Exposure time doesn't depend on aperture, but on f-ratio, and usually people want max resolution from given scope.
Very high framerate may be usable when doing luminescence imaging (with for example atmospheric dispersion corrector) - although limiting gain usually is better than super-short exposures at max gain. Here are some my Saturn examples (f/20 C11):
http://www.rkastrofoto.appspot.com/s..._gain_test.png |
Of course this is correct, but given that people generally want the highest resolution image that they can manage, they will put in image magnifiers (Barlows, Telextenders, Powermates etc.), these will of course affect the f-ratio. The larger the aperture the less of these you will have to put in to get an image of the required scale, hence the smaller f-ratio, hence a "faster" scope. So the aperture and f-ratio are inextricably linked in planetary imaging.
Cheers
Stuart