Posts Made By: George Golitzin

Nice job Stuart! Looks beautiful. Albert is a great guy--I bought the mirror for my 16" from him and he showed me around his shop...I enjoyed meeting him very much.

Couple questions--
1. Are your alt bearings just 1/2" thick? I'm tempted to try that on my next project.
2. Did you happen to use electrical conduit for the struts, or something else? I seem to recall Albert using conduit, which is kind of heavy, but readily available in many sizes.
3. How is the vibration at higher powers? I'm very curious about that.

George

No luck on m15 and m13 last night, but conditions were poor--thanks for an interesting challenge, Inge. Maybe I'll have a decent view of m22 tonight, though my southern view is very light polluted.

What power were you using when you made these observations?

-george

Floyd Blue said:

Always fun to make your own stuff and satisfying too some how.

Amen to that Floyd! Now how about a dovetail saddle? That's what I need for my little polaris mount...

But wait a minute...where do you get 3.5 lb of aluminum for $10 these days?

--george

Oh boy! Another flood of Naglers on the used market! More disruptions in our eyepiece collection! (sigh)

--geo

Nice scope Pollux--after all those cute refractors I'll bet you're enjoying the aperture!

---George

Thanks to all! As it turns out, the issue for me really revolves around astigmatism, and the ability of the 13E to take a dioptrx, which I can't do with the 13T6. Thanks to Gene Baraff's post in another thread (ethos plus dioptrx question), I was able to determine I really need the astigmatism correction at a pupil of 2.3mm--and that's exactly where the 13mm focal length puts me in my two reflectors...So I think I have my final excuse to make this ridiculous expenditure!

aperture wins. unless the c8 is from the halley comet era.

--geo.

Dale--

The angle at which the altitude pads are set depends a lot on the diameter of the bearings. As the alt pads get closer, balance becomes more critical, and altitude motion requires less force. On the flip side, closer alt pads slightly reduce the weight of the rocker. (But what really reduces the weight of the rocker is large diameter bearings.) I've got the alt pads centered at 60 degrees on my 10", and that works fine, because they are 15" diameter. I think the spacing is something similar on my 16", but with 32" diameter. I don't think I'd want anything less on either (well, I could reduce the spacing on the 16"). That angle on the pads would allow the bearings to be cut to 150 degrees. I left the bearings on the 10" at 180, and trimmed the ones on the 16" a bit. So that does allow you to save on weight. You can also remove a lot of material from the interior of the alt bearings without sacrificing stability. I do not recommend semicircular rings though--too bouncy. I built my 16" that way and later added a cross brace. Every little bit helps, and in removing material from the bearings, you're not affecting the balance much at all. If you're going to a truss scope, you can easily drop 50 pounds on this guy.

George

Wow, Jim, congratulations. What a nice problem to find oneself with! One does get used to that 100 degrees in a hurry.

I'm noticing the same non-parfocal thing with the ethos (having been spoiled so long by the naglers in this regard), and I'm in a similar situation with regard to back-focus, having just enough room inwards for the 26T5.

The instruction notes from Televue included in the 13mm ethos box that I received actually recommend using it in 2" mode with the paracorr all the way out--rather than in 1.25" mode with the high-hat adapter.

In general, I think you should avoid cutting truss poles until you have lived with a given eyepiece for a while, especially if it is usable in some fashion--that is, you can use your ethos and your 26T5 in the paracorr now, so why cut the poles in order to use the high hat adapter? Further, given the length of this ep and the resulting torque it generates on the focuser, it seems preferable to me to use it in 2" mode whenever possible. More stable. Bottom line, I'll bet the way you use it now you're not seeing any coma anyway.

Regarding the other problem, I don't see you keeping the 12T4 if you're keeping the ethos, but hold off on the 17. Some diffuse objects will appear more concentrated at lower power--for example, I actually preferred the view of M31's dust lanes in my 16T5 over the 13E the other night, as the longer ep showed the lanes with a little more contrast.

George

Now there's a dedicated amateur! Thanks for the link--Reiner has provided a very nice resource in both the hickson and abell atlases.

George