"Paul Hyndman" wrote in message
.. .

I use a Coolpix 990 and only wish it had a wider entrance pupil
(although
3.5mm, or whatever it is, is not bad).

Be careful what you wish for... the smaller CoolPix lenses help overcome
vignetting!

When using a non-SLR digicam (ie: most consumer grade models with
permanently attached lenses), vignetting seems to be far less a problem
with
those using smaller diameter lens assemblies. Vignetting with afocal
setups
can be further reduced or eliminated by using the camera's *optical zoom*
(never the digital zoom, which reduces effective resolution) and an
appropriate fl eyepiece.

If that is true, it's not due to small diameter. It's due to having the
entrance pupil closer to the front of the lens assembly.

An entrance pupil smaller than the exit pupil of the eyepiece prevents you
from using the full aperture of the telescope.