Under the "graphical plots" PLOP gives you the location of the various points on each part - the center, the ends etc. - in cartesian coordinates relative to...
Something that I've never understood clearly and hope someone here could answer. I understand all the formulae concerning exit pupil, fov and magnification, I...
... Well that also depends on the focal length of the scope. ... Because the light rays entering the eye do so at larger angles. It seems pretty evident from...
See comments in text below. ... fov ... 30 ... moon ... That was stated as a given not as a question. ... 14mm ... That and the cited article does explain it....
... Well the eye is just another optical instrument, so if you understand basic optics then that should be easy. If you want the size on the retina in linear...
Seasons Greetings! I do not know how many folks in the astronomical arena are aware of it, but this past fall Rob Teeter built a 12.5" truss tube Teeter...
I am not sure, Kyle, but they look like it. Rob Teeter could answer that question, however. He installed them. Charlie _____ From: bigdob@yahoogroups.com...
Perhaps you're not looking at it the right way. The telescope produces an image on its final focal plane. The scale of that image is based on the focal length...
... In general, yes, but the _apparent_ FOV is also involved. A narrow AFOV low power EP _can_ have a smaller field stop than a wide angle higher power EP....
Seasons greetings, Everyone! This is a brief announcement about a new product from Markless Astronomics. It is a heavy duty (#8 AWG) power cable to run from a...
John, Thanks. I stated: "For instance, if the 7mm eyepiece had a field stop twice as large as the 14, the true field of view would be the same size in both ...
I just bought a couple of University Optics Orthos (4mm and 6mm) mainly for planetary viewing in my WO 80mm refractor. I have an 18" f4.3 Dob as well and...
... Sure (as long as the AR coatings are good), although the reasons for preferring less glass is a bit different for planets. They're bright, so you don't...
Thanks John. Yes my Telekit now has ServoCat so for certain objects, FOV is not an issue. I have heard excellent things about the UO Abbe Orthos especially...
There is a discussion now on Cloudy Nights ATM on alternative laminates for alt and azimuth bearings. What have you had success with now that Ebony Star isn't...
Jim, Scopestuff has it in strips for alt bearings and in narrow-cut rings for small az bearings. They don't sell it in squares or full circles though; and the...
David, When you asked about Ebony Star, I assumed you were looking for alt. bearing material. You're building an 18", correct? Look for FRP (fiberglass...
I have used the glass board on the AZ on small scopes such as the Antares 12" tube dob with success. It does seem to be a bit smoother with heavier scopes...
I think FRP is even preferred over ebony star for az bearings on larger dobs. It's available at most of the big home improvement stores, about $25 (IIRC) for a...
Why would it be preferred? How is the application different than for alt bearings? It seems like you have similar forces and the need for similar friction. ...
... I'm not quite sure myself, but I've only heard of it being used for az bearings, not alt. One possible reason is that it's a stiffer material, so I don't...
My 10-year-old Obsession 25 has FRP for both alt and az bearings, from the factory. It works fine. My much newer 30, on the other hand, has FRP az and Ebony...
True. It is preferred for ALT bearings on larger Dobs. Charlie _____ From: bigdob@yahoogroups.com [mailto:bigdob@yahoogroups.com] On Behalf Of John Mahony ...
For the underside of the mirror box, I like to use FRP, which stands for Fiberglass Reinforced Plastic. There are several makers of it, a well-known brand...
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