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"Kidney-bean" effect in ETX-125

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#1 Michael Rapp

Michael Rapp

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Posted 11 July 2004 - 04:52 PM

My low power eyepiece is a TV 32mm Plossl. I recently bought an ETX-125 to use when I just didn't feel like lugging out my Meade 8" f/6 (fl 1220mm) reflector.

One thing I noticed is that in the ETX (f/15, fl 1900mm), I get a pronounced kidney-bean effect with the 32mm. It's difficult to find the center spot in which all of the FOV is visible.

Why is the difference between my two scopes so pronounced?

I remember trying out a 40mm Plossl on my reflector and found at that low magnification the . . . image (for lack of a better term) of the secondary became noticable and I opted to stay with the 32mm. Is something similar going on here?


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