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David Knisely - A Night With a Few Variables

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A Night With A Few Variables

By David Knisely, KA0CZC, dk84538@navix.net

On Wednesday evening September 9th [1998], Dave Hamilton and I headed out to the Olive Creek State Recreation Area, southwest of Lincoln, Nebr. for some much needed observing. We were tired of the lousy observing conditions over the past few weeks, so even though the waning gibbous moon would be rising around 10 p.m., we still decided to "just do it", to satisfy our observing hunger. I arrived a little after a colorful sunset under a nice clear sky, and, after setting up my ten inch f/5.6 Newtonian, used my 10x50's to watch a nice Blue Heron do his thing on the north side of the lake just below the dam while I waited for Dave Hamilton. Dave H. pulled in and began to set up his 12.5 inch f/4.8 Portaball, with its newly-installed Telrad/secondary mirror heaters and the new Telrad "cross" reticle. The Milky Way appeared beautifully, but for once, we let the real Deep-sky take a backseat so we could experiment with a different kind of observing activity, which if successful, might just fill the nights when the moon drowns out the really faint targets.

Dave H. has just joined the American Association of Variable Star Observers (AAVSO), so we decided to try our luck with the small group of variables which Dave H. had been assigned to monitor. We began with the long-period variable T Cephei. This one was fairly easy, as it was bright enough to show its reddish color, standing out well from the fainter stars. I don't recall what magnitude we assigned to it exactly, but it seemed to be around 8th. The AAVSO charts (provided with membership) for the star made locating and doing a magnitude estimate fairly straight forward. The next stars on the list were V and R Cassiopeiae, which were also fairly easy, but not as bright as T Cephei. The AAVSO "a" charts sometimes were for more than one variable, and thus did not always cover the entire region around a particular target star. This occasionally made the initial location process a bit more difficult. I found that I could use my old right-angle-sweep finding technique with my equatorial mount to get to each field fairly easily, but sometimes I had to refer to the wider field of Uranometria to make certain I had hit the right area. Since these variables were all shown on Uranometria, I quickly stopped using the AAVSO wide field charts for the location process. I seemed to be beating Dave H. to each variable after that. R Vulpeculae gave us a few headaches, since the field was fairly rich in stars, and there was another variable next to it. After a lot of running back and forth from the charts (and putting Dave H's wide field eyepiece in my ten), we finally nailed this fainter star.

We thought we were doing pretty well until we tried T Herculis! Although the field was easy to locate, seeing which star was actually the one in question was a bit trying. I found that I liked the older Telrad ring reticle a lot better than the "cross" one in Dave H's unit. The variable was around 10th magnitude, and, with the rising of the moon, was a bit faint and more difficult to pick out from the numerous similar-magnitude stars in the area. Still, we both agreed on the magnitude estimate, and took a break to look at Jupiter. Dave bought a 5mm Pentax eyepiece, but to his chagrin, he couldn't get it to focus in the Portaball. We tried it in my ten, and with the wider focal range of my focuser, we did get a good focus. While it gave a slightly wider field of view than my 10mm Ultrascopic and 2x Barlow, the overall performance was about the same, so I wasn't all that impressed with the Pentax. However, when Dave brought over his Meade 8mm Ultrawide, all I could say was WOW! It was most impressive on the moon, and was tack sharp both at the field center and the edges. His 14mm Ultrawide was equally impressive (I guess I will need to get a new eyepiece box soon). Jupiter showed the "Little Red Dot" spot in the south temperate belt, along with a wealth of other interesting detail. Saturn was also nice, but not as good as several nights previous.

As a final target, we went after the dwarf nova SS Cygni. Normally, this star is fairly faint (about 12th magnitude), and sits in a fairly rich field, so we weren't all that optimistic about being able to see it. The moon light was really hampering finding visual guide stars, so we verbally expressed more than a little frustration as we hunted for it. Finally, the words, "GOT IT!" exited my lips. I was surprised to find that we caught SS Cygni in one of its 8th magnitude outbursts (about 8.3 was our estimate), and it wasn't difficult at all to see. Once we finished with it, we did the usual tear-down of equipment, followed by a few minutes of just talking about all that we had done. I found David Levy's book on observing variable stars for beginners to be an interesting introduction to this fascinating aspect of our hobby which effectively puts your finger on the pulse of a star. It looks like I too will be getting out to observe more often, as I follow the progress of these interesting stars. Clear skies to you.

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484