Quote:
Originally Posted by naskies
All else being equal, the same star with a larger aperture scope will give either a higher ADU count, or a shorter exposure for the same ADU count (therefore higher tracking rate).
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Dave, if you double the aperture of the scope and keep the focal ratio the same, the guide stars will indeed be 4x brighter.... however, because the image scale is increased by a factor of 2x, you will have to increase the guiding chip area by a factor of 4x to capture them or accept that there will be only a 1/4 of the number to choose from. The corollary to this is that if you halve the aperture, your selection of guide stars changes in so much as you have 4x the number of guide stars rendered at 1/4 the apparent brightness....some of the new ones coming in to the field however, will be on average 4 x brighter. ergo, large telescopes don't render star field richer, just more resolved.