About two months ago on a rare clear night I noticed that in focus star images on my C14 were showing flare with a 40mm eyepiece and also were showing classic oblong shapes at 90 degrees to one another on both sides of focus.
I felt a sinking feeling and concluded that somehow the secondary must have got loose on the corrector. The secondary mounting is generally snug, rotates with hand pressure, but I was thinking, well, maybe some ignorant person turned it at a star party, or I twisted it by accident, or something.
So I proceeded to evaluate the secondary mirror different positions, moving 1/8th turn each time.
(Meantime everyone around me is having observing fun.)
I was at position #6 and thinking the view was pretty good when perchance I came at the eyepiece from a different angle and noticed that the astigmatism was differently skewed.
Then came the DOH! moment.
My 40mm Pentax XW has a dioptrx on it. And I ain't just anyone. I'm the guy who wrote and posted the article on how to put a dioptrx on an XW40.
The scope was never showing any astigmatism, and the eyepiece only showed it because I had put an astigmatic corrector on it to counteract my eyeballs.
I lost about an hour to all this. It shows the terrible effect that long weather-enforced abstinence from viewing can have: one's equipment becomes a stranger. I forget what I have, and also how to set up what I have.
regards
Greg N
I felt a sinking feeling and concluded that somehow the secondary must have got loose on the corrector. The secondary mounting is generally snug, rotates with hand pressure, but I was thinking, well, maybe some ignorant person turned it at a star party, or I twisted it by accident, or something.
So I proceeded to evaluate the secondary mirror different positions, moving 1/8th turn each time.
(Meantime everyone around me is having observing fun.)
I was at position #6 and thinking the view was pretty good when perchance I came at the eyepiece from a different angle and noticed that the astigmatism was differently skewed.
Then came the DOH! moment.
My 40mm Pentax XW has a dioptrx on it. And I ain't just anyone. I'm the guy who wrote and posted the article on how to put a dioptrx on an XW40.
The scope was never showing any astigmatism, and the eyepiece only showed it because I had put an astigmatic corrector on it to counteract my eyeballs.
I lost about an hour to all this. It shows the terrible effect that long weather-enforced abstinence from viewing can have: one's equipment becomes a stranger. I forget what I have, and also how to set up what I have.
regards
Greg N
"Scope will get you through times of no money better than money will get you through times of no scope." --Freewheelin' Franklin
