Unfortunately the Naglers do not do that well at high power because of the number of elements. I have found that good plossls, the Takahashi and the monocentric are the best performers. I have a 4.8 Nageler, a 4 mm Takahashi and the 6 mm TMB previously noted. Both the Takahashi and the TMB are better for fine detail than the Nagler but they have narrow fields of view. The collimation of the Ealing may also be a factor but so also may be the atmosphere. Even though the seeing may appear calm, at high power the detail may not be there. I have seen a significant difference in the image quality at Wolf Creek on a good night versus lower elevations. One night at Wolf Creek we split Beta Delphinus at the time .5" with an 18 inch Starmaster (with tracking) at 900x. I normally can not use more than 300-400x without the stars "smearing" in Sandy with the same scope. -----Original Message----- From: utah-astronomy-bounces+djcolton=piol.com@mailman.xmission.com [mailto:utah-astronomy-bounces+djcolton=piol.com@mailman.xmission.com] On Behalf Of Kurt Fisher Sent: Friday, April 27, 2007 1:29 PM To: utah-astronomy@mailman.xmission.com Subject: [Utah-astronomy] Observing notes - Ealing 4-26-2007 Lunar visual 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 _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.utahastronomy.com