... Such ideas have been under consideration, especially in the cold of winter and the height of mosquito season. We have a nice south facing window, up well...
... Tom, Thanks, but some of my posts take more than 12 hours to show up! I've sometimes resent messages to this group and others, and then they both wind up...
A friend has a new modest sized APO and he has been busy star testing it. He is a little puzzled by the results. I gave him my thoughts, and promised to...
Definitely encourage him to do a Roddier test. It's easy and quantitative, not subjected to the vagaries in interpretation of a visual star test. Several...
2 old posts on this, here ya go; (1) from me, On my scope I had the inside focus circles perfect, but on the outside, I could make out the circles, but they...
Rich Interesting discussion...... I am curious your comments on this..... If larger diam. focusers were more commonplace, say 3 - 4", and wider diag. and EP's...
Alan; You are NOT being moderated on this group. Currently new members are automatically on moderated status when they join. After a first acceptable, non...
Bill; With current configurations of scope color correction suffers considerably as F ratios are decreased. Other optical aberrations also increase in...
Rich my Antares 152 f/6.5 required an 1nch and a half removed from the focuser drawtube of the R+P focuser to obtain a fully illuminated non-vignetted field of...
Rich, good points...... Since the f6.4 Scopes, like the SV4 are forced to be a triplet for correction, so I imagine, getting below f6 range would require too ...
Stan; At least you recognized the problem and dealt with it, as Antares has done via the shorter focuser tube on the current scopes. IMO though yours should...
I agree Rich it truly makes you wonder how many scopes out there are operating at reduced aperture with the drawtube or baffle vignetting issue. I have a sight...
Bill; A lot depends on wanted color correction. Remember the SV Nighthawk II is an F6 achromat and it works fine as long as the CA is not too objectionable to...
In another discussion, someone has commented that ghosting tends to compromise the lunar and planetary performance of uncoated achromats. This was not my...
Ghosting in Uncoated Achromats Alan home-made, 76mm/f18, uncoated. Never noticed any ghosting. Person I knew bought a 4" coated achromat, borrowed my 76, sent...
... knowledge plus the skill with math, to answer the question: "Given an achromat with a finite amount of reflection from each glass-air interface, is there...
... That should have been : "I have the impression that YOU have the computer program and/or the optics knowledge..." Apparently, a whole line of type got...
I'm glad you asked the question because I am contemplating a 7" f/15 lens. I still have to decide on coated or uncoated. Most of my experience is with the 9"...
... If I remember correctly, you'll lose about 4% at each air to glass surface with an uncoated lens. With coatings, you'll lose about 1/2% per surface. So...
Hi Gene, I have played with some designs with ATMOS, but hardly consider myself an expert. I haven't done anything related to ghost images. I know Zemax ...
Are you selling the 102 to move up to the 130? An alternative plan would be to keep the 102, sink the $3.7k into a better mount and side-by-side mount the 102...
In the real world of observing, do these ... details? If you star test an uncoated doublet expect to see brighter and more rings compared to a coated apo,...
Hi Alan, While in school, I used 2 Clark refractors with uncoated lenses: a 6- inch (used by Burnham) and a 15.6-inch (Washburn Observatory). Neither had a...
Alan; I never noted ghost images in either the Chabot 8" Clark or their 20" Brashear. It is my understanding that some designs, including some early Clark's,...
Ghosting will occur in a doublet objective if the inner radii are very close to equal in radius, and can occur whether they are closely spaced or spaced far...
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