Notes from Under Sky

Wocket Gets Racked! (Film at 11)

In which the Tele Vue Ranger gets a solid mount

After a few entertaining but frustrating months of dealing with an unbalanced Tele Vue Ranger (on my light-duty fluid pan head tripod), I finally got my Up-Swing mount last night. I had priced the Tele-Pod, which is Tele Vue's combined tripod plus Up-Swing mount, but it turns out it lists for about $360, a bit high for a scope that I bought for barely 10 percent more than that.

So I decided to scour the used market. I took a brief look at Astromart, and there was an add for one, but by the time I contacted the seller, he had already sold it. Fortunately for me, another seller came on line just a couple of days later, this time with the Up-Swing head on a Bogen 3021 tripod and 3030 head. A sturdy combination, and the price was right. Thanks to Ben Kolstad for tipping me off to this ad; I would have missed it otherwise.

Attachment is a snap; the head is custom-designed for all of the Tele Vue telescope brackets. And I must say, it works exactly as advertised; the alt-az motion really is quite smooth and nearly weightless. With minimal tension on the altitude bearings, the scope maintained balance, from horizon to zenith.

Such robust balance also allowed me to figure out a good way to use my Barlow and 6 mm Radian together. As I mentioned here in a post earlier this year, I had trouble reaching focus with my particular Barlow (the Orion model) and the 6 mm Radian; insufficient out-focus without the diagonal, and insufficient in-focus with the Barlow. It was also a big pain to adjust without good balance.

Last night, the mount made it possible to wrestle a little more freely with the optical components. It turns out that there is just enough out-focus with the diagonal between the Barlow and the eyepiece. This kind of combination is traditionally said to yield a 3x power amplification, but I found it to be slightly less than that. Based on the drift method, some basic math, and the low-distortion Radian, I estimated the magnification in this case to be about 205x +/- 15x. (I am quite sure I could lower that error bar, but I'll do that some other time.) The magnification of the Radian alone is 80x.

It turns out that this magnification is just about what the Radian by itself gets in Opus, my 5-inch SCT. I didn't have time to do a side-by-side last night, but I will do so some time this planet season. On this night, 205x was enough to get me the NEB and SEB (of course), the GRS, and the NTB. Seeing did not cooperate. Cassini was obvious, but more so at 80x than at 205x. I think there is nothing intrinsically bad about this set-up, however; I only need to wait for good seeing to take advantage of it.

The sky was also partly cloudy last night, which didn't affect Jupiter, but at one point in time I couldn't see the Pleiades. This afforded me the opportunity to star-hop to M45 through the Ranger at 15x, a kind of entertaining exercise. It had cleared up a bit by the time I got there some 2 minutes later, so I could have just waited, I suppose, but the view once I arrived was splendid; I didn't care how I got there.

Copyright (c) 2000 Brian Tung