2 replies to this topic

[celestial_search]

I recently purchased a Celestron f/6.3 focal reducer/corrector in order to begin CCD imaging. Earlier this evening, while it was still light out, I set up my mount, scope, etc. I put the focal reducer on and then the adaptor that holds the diagonal. I focused on a telephone pole top about 2.5 blocks away (I didn't have anything farther away to focus on because of trees). I noticed that after I had the top of the pole focused without the f/6.3 reducer and then put the reducer/corrector on, I had to dial in quite a bit to get the pole in focus.

I did notice, however, that in the center of the 40mm EP there was a slightly noticeable circular blurr that must be the central obstruction.

Is this circular "blur" in the center of the EP because it was light out and the target was real close? I hope that when observing an object at "infinity" when it's dark that the blur won't be as noticeable. There is no visible marking or dirt on the brand new reducer/corrector and the EP likewise had a clean lens.

Thanks!

[jrcrilly]

I did notice, however, that in the center of the 40mm EP there was a slightly noticeable circular blurr that must be the central obstruction.

Is this circular "blur" in the center of the EP because it was light out and the target was real close? I hope that when observing an object at "infinity" when it's dark that the blur won't be as noticeable.

You'll be OK. It's not the distance but the exit pupil. At F/6.3 the 40mm eyepiece has an exit pupil of 6mm. In daylight your eye pupil is much smaller (1-2mm) so the obstruction is effectively much larger. At night your eyes should open up to 6 or 7mm, so the obstruction won't be effectively magnified.

[celestial_search]

Thanks!