Quote:
Originally Posted by Don Pensack
As magnification is increased, the stars do not get dimmer, being points, but the background sky does, being now spread across a larger apparent field. In fact, a doubling of the magnification reduces the brightness per square millimeter of the background sky by a factor of four.
Accordingly, fainter stars are visible at higher powers.
Once the magnification is high enough the Airy Disc (or spurious disc, if you prefer) becomes visible, increasing the magnification more does not bring in fainter stars.
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Don,
I agree with you on nearly every point except that I believe stars must get dimmer at higher magnifications just as everything else does. This is more noticeable in a scope of smaller aperture. The only reason I can think of for fainter stars still being visible at high magnifications is your point about the dimming of the skyglow.
Curiously, in an article on scopecity.net (Optical Terms and Characteristics of Telescopes), it states that the stellar limiting magnitude of an 8" scope is 13.3 at 28x but this increases to 16.1 at 320x.
This I cannot understand. Anyone any clues as to how this can be possible?
Regards, Rob.