June 30, 2008

Giro III & the C8

Last week I found the sky had cleared about 12:30 am and went out for an hour with this setup. The tripod is my own, homemade, walnut, not yet finished but very sturdy. That's the 100mm f/6 on one side, and the C8 on the other. In between is the Giro III that was my Christmas present (I have a very understanding bride who this year let me pick my own present). Just under the Giro III and above the tripod hub is a 60mm-wide rubber washer I obtained from Lowe's.

The Giro III is a fine piece of work. The C8 with the WO focuser and the 8mm Baader eyepiece is pretty heavy, but the Giro III handles it quite well. The 8mm provides a magnification of 254x. I thought that might be too much for the mount, but it was not so. The field of view is very small, just a quarter of a degree. To illustrate, M13 pretty much filled the view. I was just able to put Jupiter and three moons in the view; the moon furthest out would not fit or just barely fit with the planet quickly moving outside the view (Jupiter was awesome to behold that night at that magnification). Most things I see in that view disappear in about a minute tops, and they filled the middle 50% of the view for only 20 or 30 seconds. That means that I have to move the scope often. Moving the scope is not a problem, really, for me: I'm a dob fan. But dobs are so large. With the Giro III, I was hoping to get the benefits of a dob mount for my refractors and SCT. And that's about what I have. The primary issues for a mount of this type are, for me, backlash and settling time. Settling time is less than a second with this setup (with my rubber washer in place), and that's if I actually move the tripod. Just rapping on the tripod does nothing. Bumping the scope itself requires the less-than-a-second settle. If the scopes are balanced well, there is virtually no backlash. On this night, I was balanced a little too far backward for work at the zenith and tightened down the altitude axis to compensate, and even then the backlash was only 0.03-0.04 degrees, well within workable limits, even at 254x. I will definitely not hesitate to put the 8mm in again.

There are some drawbacks. My eyepieces do not all weigh the same, and sometimes I have to re-balance when switching eyepieces. That's a pain if I have to find objects twice. But the virtue of the dual arm setup is that I do not need to switch eyepieces. I use my 4-inch as a giant finder (35mm ultrascopic eyepiece, 17x) and the C8 for a closer view.

[Update: I later removed the rubber washer. The mount handles vibrations almost as well without it, and I was continually (once every four or five uses) having to tighten the bolt holding the mount when the washer was in place. On balance, I decided it was not worth the effort. The mount performs beautifully without it, too.]

June 25, 2008

Draco's Nose

I took the 100mm f/6 out last night for a short session. After a quick look at Jupiter (with Ganymede on one side and the other moons all grouped on the other), Albireo, M29, M27, and M22, I turned the scope to Draco's nose.
First, I found NGC 6229. This is a globular cluster in Hercules just south of the nose. Appearing much smaller than M13 or M22, and not nearly as bright as M92 just to the southeast, still NGC 6229 was not hard to find. It sits next to a couple of stars and the three objects together make a nice equilateral triangle. I could make out no individual stars in NGC 6229, but given that the globular is about 100,000 light years away, much further than M13 or M22, that's not surprising.
If Draco has a short nose, Al Rakis or Mu Draconis is it. It's a nice double star of about equally bright components that was split at 75x through the 100mm. It looks a little like Gamma Virginis---two tiny headlamps---only appearing a bit further apart than that system right now.
If Draco has a long nose, 16 & 17 Draconis is its tip, also a splendid view. 17 is a double, so the whole is a triple system resembling Mizar and Alcor somewhat, but closer together. 17 was also split at 75x.
I will definitely go back to these doubles soon.

June 19, 2008

Outreach & Navasota Storm

Last night I drove about an hour west to a young women's camp experience that my church organizes. A large group of campers and I talked for a bit about planetary orbits, and the planets' current locations, and then hit the telescopes. It was cloudy for part of the time, and this discouraged some, but those who stayed were rewarded with some nice views of Saturn and Jupiter through the XT8. Others watched the moon, which was full tonight, through the 100 f/6. My amazing daughters helped others look through the scopes.

After the young women left for their tents, a storm approached. It was never closer than about 20 miles, I think, but it looked ominous and for a while generated lightning about once every three seconds.

June 3, 2008

Jupiter & Sagittarius on June 1

This image is an 8-second shot with the Sony DSC-75, dark subtracted, color adjusted, resampling filters applied, and resized in Registax.

June 1, 2008

First Light with Little Red, and a First Observation of M94

Last night was lovely. I received a new (used) scope in the mail this last week: a bright red (anodized) AT66ED (f/6). It's a small scope, but it's a real performer! I hung it on one side of the Giro III and the Orion 100mm f/6 achromat on the other. I put a 24mm eyepiece in Little Red for most of the night, for about 16x, and an 8mm Hyperion in the 100, for 75x.

Some clouds passed by around 11:40, and then the night was grand. I first stopped at M94. This was an item on my "yet-to-see" Messier list. But no more "yet." There it was in the 66's view, and much brighter in the 100. In fact, I believe I could see a dark marking on the galaxy in the 100. I'd be curious if others see that.

I also found M63 again, but it was dim. Mostly, it was a grand night for globulars: M13, M4, M56, M22 (the Great), M28 (surprisingly bright), M54, M70, M69. Contrasting these is an interesting enterprise. More stars were resolved in M28 than any other. M4 always seems a bit under-populated for such a bright object. I am always disappointed that I can resolve so few of M13's stars in these smaller scopes. M28 was so bright I spotted it easily in the 66. It is almost as bright as M22, but appears perhaps only 25% as large.

I also observed M57 and M27, and M8 and M21. Jupiter was up, with two Galilean satellites on each side of it, as if the planet were a judge trying a case, with the parties and their lawyers sitting before him. I also looked at Cor Caroli, Albireo, and Epsilon Lyrae.

What most impressed me during the session was Little Red's performance. One could easily come to prefer the APO above other scope designs. I could see most of these deep sky objects in Little Red: M13, M4, M56, M22, M28, M57 (a tiny little ring in a very wide field), M27, M8, M21, M94. I was surprised. Increasing the magnification did not dull performance at all, but enhanced it. Jupiter looked every bit as good in Little Red at 80x as in the 100 at 75x---perhaps a little better because the planet lacked the slight purple halo the achromat always shows. And Little Red split the components of Epsilon Lyrae cleanly at 80x, a better view than in the 100 at 75x. Of course, the 100 gave everything a much brighter view, and the objects I could not see in Little Red I could see clearly in the 100, but Little Red did what it is supposed to do: Show high-contrast, wide-field images, and when magnification is pushed a little higher, continue to show very fine detail per inch of aperture.