Quote:
Originally Posted by ausastronomer
Hi,
This is not correct. It is a very common mistake. These two things are solely dependent on the focal "length" of the telescope, not it's F-ratio. The F-ratio is a function of the focal length and some people incorrectly attribute the change in magnification and FOV when the F-ratio changes, to the change in F-ratio, but it actually happens because the focal length changes.
eg. a 10"/F5 telescope with a 10mm eyepiece has the same magnification and FOV as a 5"/F10 telescope, with the same 10mm eyepiece. Same focal length = same magnification and FOV, but not the same F-ratio.
Cheers,
John B
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i know all this,
thats why i was very careful to say F-"size" meaning focal size, and length, and made sure i didnt say F-ratio
