In article , Mick wrote:

"Magnus Nyborg" wrote in message
...

"Mick" wrote in message
. ..
Ok..so I took a toilet paper roll and looked at the waning crescent
moon this morning at 4:30 local time. I could see enough
earth shine to complete the disc...there is NO WAY Mars comes even
close at 120 X's magnification to being a comparable
angular diameter in the EP....the math says yes..my eyes say NO!
Go figure...

That's why it is concidered an illusion - a direct comparison (the
magnified view of Mars in one eye, the non-magnified view of
the Moon in the other) eliminates the illusion.


You seem to pass off "illusion" as nothing more than the natural
biological function of taking a leak... the fact remains that
the moon will always appear larger in the sky than
Mars will appear in the EP...

There *is* the possibility that your "120x" eyepiece isn't really
delivering 120x -- that its focal length is longer than it claims,
or that your telescope's FL is shorter. I say this just to be
contrary :-)

Hmm, how could you measure your 'scope's magnification by looking
through the eyepiece? The only way I can see to do it
would be if you could gauge the apparent angular field (tricky,
but less prone to illusion than looking at tiny objects on the field),
then measure the true field by turning off the clock drive (if any)
and timing passage across the field.

Any better ways?

Stuart Levy