Don Colton wrote,
I question whether you will get diffraction effects based on aperture on the moon at 560X with the Ealing. . . . . You may, also, be getting deterioration of the image due to the quality of the eyepiece. I have found some eyepieces perform very poorly at high power.
Good point. I do have low-end eyepieces and did not try my one 20mm Nagler. The specific lunar test for diffraction deterioration that I use are fine rilles - like Rima Gay-Lussac (Rukl 31) mentioned in the prior post. At lower magnification, the rille was crisp. At extreme power, parts of the rille visible at lower power, appeared broken and merged with the surrounding terrain. This visual effect held even during periods of calm - thus ruling out atmospheric turbulence as a cause. My understanding is that this is an effect of the diffraction waves overlapping each other at extreme mag. But the low-end eyepiece probably is the right cause. - Kurt _______________________________________________ Sent via CSolutions - http://www.csolutions.net