Lester
12-02-2012, 03:03 PM
Hi all,
can somone inform me as to what is the relation of aperture to limiting magnitude. I have been trying to mount my Takahashi Astrograph 160mm diameter, piggy back on the 14" SCT but the Losmandy brackets are not solid enough as the smallest tap caused the Astrograph to resonate.
I want to try for Comet Lovejoy tonight, as the Moon will be rising late enough for me to have dark skies before hand. I will be using 77mm diameter 70-200mm FL canon lens instead of the 160mm diameter Astrograph.
Is it just a matter of squaring the diameter of both optics and dividing the lesser into the greater? eg. 160x160= 25600, 77x77= 5929
25600 divided by 5929=4.3 . I think each magnitude is 2.5x fainter. So 4.3 divided by 2.5= 1.7 magnitudes less with the 77mm diameter lens.
Appreciate your input.:thumbsup:
can somone inform me as to what is the relation of aperture to limiting magnitude. I have been trying to mount my Takahashi Astrograph 160mm diameter, piggy back on the 14" SCT but the Losmandy brackets are not solid enough as the smallest tap caused the Astrograph to resonate.
I want to try for Comet Lovejoy tonight, as the Moon will be rising late enough for me to have dark skies before hand. I will be using 77mm diameter 70-200mm FL canon lens instead of the 160mm diameter Astrograph.
Is it just a matter of squaring the diameter of both optics and dividing the lesser into the greater? eg. 160x160= 25600, 77x77= 5929
25600 divided by 5929=4.3 . I think each magnitude is 2.5x fainter. So 4.3 divided by 2.5= 1.7 magnitudes less with the 77mm diameter lens.
Appreciate your input.:thumbsup: