Posts Made By: Jim Richberg

I'm a manager in one of the new (post 9/11) Federal agencies in Washington DC. Designing and building scopes is very much a stress reducer for me (as much or more than observing is!), in part because it is a) something more concrete than the usual problems I deal with and b) somewhat more under my control (all but the observing part. )

My ATM'ing training consists of a semester each of woodworking and metal shop some 35 years ago...
Jim

Jon,
I've got about a half-dozen pages about the PST and budget white light solar observing on my astronomy web site, including observing tips, eyepiece reviews, and mounting options (check out my H-a, CaK, and white light triple mount "Uncle Beasley"!) Feel free to peruse it and I'll be happy to answer any questions.

Jim
The site is located at
http://www.jimrichberg.com/astronomy/solar_observing.htm

Tom,
If you're not dead set on having LED's, I'd take a serious look at the "Astro-Glow" material sold by http://www.astronomy-shoppe.com/

While they got started selling sets of illuminated numbers for labelling eyepieces, the store also sells strips of the material in a set called 'Tri-lineators' intended specifically to use on tripod legs. This stuff is *very* luminescent and glows all night long, in my experience.

The proprietor is an old observing buddy of mine, and gave me some samples at WSP. Take a look at how far I was able to make them stretch-- on ladder treads, Dob handles, knobs, eyepieces, and a name tag. Images can be found on my page at
http://www.jimrichberg.com/astronomy/User%20friendly%20mods.htm

The bottom image on that page -- of my name rendered in leftover bits of Astro-Glow-- shows you exactly how brightly this stuff is! http://www.jimrichberg.com/astronomy/ag%20Jim.jpg

Like Byrll Cream, "a little dab'll do ya" -- I think I did all of my applications using about as much of the material as you'd get in an $8 order of the Tri-lineators.

Worth checking out, in my opinion.

Jim

I've used metal slings on both my 16" and 24" Dobs, and my solution to avoiding stiction has been to wrap adhesive-backed teflon tape on both the sides of the mirror and the face of the sling. The coefficient of friction for teflon on teflon is ~0.04 -- about as low as you'll find for *any* materials. (For reference the coefficient for steel on glass is between 0.5 and 0.7)

I've successfully used my 24" Dob to point at Omega Centauri from mid-Atlantic latitudes (Virginia), so this Teflon/sling combination performs well down to what are essentially horizontal viewing angles. FWIW, this sling replaced a conventional nylon one on my 24" scope; part of my motivation to change was watching the primary move over 1/2" in the scope between night and day at WSP two years ago in response to changing temperatures and humidity. The new steel sling is basically insensitive to these environmental factors.

I have used both thin tape and wider 'bumpy' textured teflon tape, and make my slings out of different thicknesses and widths of steel lumber strapping tape. (I wanted some 'give' in the sling supporting the relatively light 1/20th wavefront 1 3/8" thick 16" mirror, whereas on the 75 pound 24" I was looking for something stiffer.)

You can see examples of both slings and types of tape on my web site, http://www.jimrichberg.com/astronomy/
Insert "sling" into the FreeFind search tool in the upper left corner hand side of my home page and you'll find a half-dozen photos or references to the slings' performance.

Clear skies,

Jim

Looking for a wide field compliment to my 24"f/4 Dob, I ended up getting one of those inexpensive 120mm f/5's to try. I modified it fairly heavily by shortening the drawtube and removing some of the baffles-- both of which had contributed to vignetting -- and flocking the inside of the OTA.

Outfitted with a Nagler 31 and MaxBright 2" diagonal-- both of which I already had-- it renders a 4.24 degree FOV and a crisp and bright view which trounced smaller refractors and a pair of 20 X 80 binos in testing. At 19X the limitations of an inexpensive achromat are not bad, and 120mm of aperture offers enough light grasp to yield a view that starts looking like a 'real telescope' under dark skies. To be honest, the real key is the Nagler 31 eyepiece -- using cheaper eyepieces like the 30mm Widescan III clone rendered a view that was abysmal.

Here is a link to the mods I made:
http://jimrichberg.com/astronomy/Orion%20ST120.htm

and here is one to the testing I did against a Televue Ranger, ST80, and the 20x80 binos.
http://jimrichberg.com/astronomy/refractors.htm

Jim