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Is this a true statement?

Started by dhvd79a, 10/14/2003 06:53AM
Posted 10/14/2003 06:53AM Opening Post
Lmagnification with an SCT = greater chance to see(notice) the central obstuction.

This weekend I was "tweaking' my finder scope and decided to take a look at some trees off in the distance using a 2" university optics lense that came with my scope. Don't have it in front of me but is is larger than 40MM possibly 50MM or 60MM can't remember which.

I looked and there it was, the central obstruction. Was it the lense size or some other lense characteristic that made the CO so obvious.

This was in bright daylight BTW

Thanks
Dave
Posted 10/14/2003 07:17AM #1
It is a true statement, but *especially* true if you're using low magnification in relatively bright conditions (such as daylight, as you were doing, or looking right at the Moon). The reason is that in bright conditions at low power, the pupil diameter of your eye will often be much smaller than the exit pupil of light coming from the telescope. At some point the shadow of the central obstruction down the center of the light path starts to dominate the column of light that's actually getting past the constricted iris on your eyeball. You see 'the shadow'.
Posted 10/15/2003 10:39AM #2
Thanks for the replies. Just wanted to be sure that seeing the CO wasn't a sign that I am losing my mind. 8)