Quote:
Originally Posted by Don Pensack
Stopping down the mirror will reduce the brightness of the image, but using a different eyepiece does not.
Larger eyepieces see a larger portion of the telescope's focal plane (hence, a larger field of view), but they cannot make the star images brighter and they do not use any more or less of the mirror's surface.
Hope that explanation makes sense.
Don
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Don,
I'm not clear on one point. If the entire primary mirror is utilised by any eyepiece, why does the brightness of the field reduce at higher magnifications? If an eyepiece uses a smaller portion of the telescope's focal plane, resulting in a smaller exit pupil, isn't this equivalent to reducing the aperture size?
Regards, Rob.