Observing report for 8 February 1997

Location/Conditions

Gear

Objects

Comet Hale-Bopp, Gegenschein, Omega Centauri

Report

Here's another long observing report with some interesting twists involving a sherrif's deputy, the Gegenschein, a high-latitude sighting of Omega Centauri, and some notes on Hale-Bopp (this is at the very end, if you want to skip the rest of the report).

"Do you want to do some astrophotography tonight?", said my officemate, Jeff. After some snow the last couple days, it was really looking good for Friday night and I was contemplating what to do. He was planning on going to a University site with AC power and some amenities. That sort of fell through, and when I decided that I would astrophotograph from my usual spot 8 miles west of Laramie from 10pm-midnightish, he decided to meet me there. However, he declined to join me for a second session from 5-5:45am for Hale-Bopp.

My early astrophotography plan was to get some shots of the Orion area with my 50mm lens for an ongoing test of several films. Next, some shots with a 135mm lens to capture several asteroids near opposition. Finally, I wanted to get a good shot of the Gegenschein.

When I left home, my thermometer had just dropped below zero (Farenheit), on it's way to the forecasted low of 5-15 below. I arrived just before 10pm (5UT), to an unexpectedly empty parking area. However, as I was polar aligning my barndoor mount, a vehicle pulled in which turned out to be Matt, a 1st-year graduate student in the department. Five minutes later, Jeff rolled in. Since he didn't have AC power, he hadn't brought the C8. However, Matt had never really been an amateur astronomer; also, not being used to real winter weather, he was cold. Thus, the two of them headed back into town for the scope and for Matt to get more clothes while I was tracking a 9 minute exposure on Orion.

Just after I finished this exposure, a car slowed down while passing the area, and turned around. I guessed that it was law enforcement, and was pleasantly surprised when he cut his headlights down to running lights. He pulled alongside me and as it turned out, he was a sheriff's deputy and somewhat of an astronomy buff (when Jeff got back, he suggested that it was probably the same guy that he had talked to before out there). I ended up chatting with him for almost 20 minutes, just basically doing the usual amateur astronomy public outreach kind of thing. No calls came in while he was there ;).

After he left, the only problem was that my camera had been on, sitting in the cold with batteries that had repeatedly experienced cold weather. Thus, after another exposure, I had to change batteries. I was just finishing my Orion stuff when Jeff and Matt arrived. I spent the next half-hour shooting frames containing asteroids, listening to Jeff rave about the sky conditions and the views of some showpiece objects he was finding for Matt. From the sounds he was making, the Double Cluster seemed to be Matt's favorite ;).

My final shot was a 10 minute tracked shot of the Gegenschein, which was an easy naked-eye object as it had been earlier in the week for me. In fact, Jeff and I both found it "easily" visible with *direct* vision, an observation I had made before but kept to myself because I wasn't sure that it was really possible.

After I finished photographing, I got Jeff to test his naked-eye limiting magnitude. I tried as well, but my damn glasses kept fogging up which wasn't helping. Jeff wears glasses, too, but I was wearing a balaclava which tends to restrict airflow around glasses (and after standing outside for two hours straight, I wasn't about to take it off!). Anyway, both of us were able to see a +6.7 star near Polaris, and Jeff was possibly making a marginal observation of a +7.1 star. Unfortunately, there aren't any stars in between on the RASC Handbook chart; I suspect that my limit at Polaris would have been +6.8 and his +7.0 (the 0.2 magnitude difference is about what I would expect between us).

We all left at about 12:30am, and I waited around until 4:30am to load the car back up and head out again. There was some patchy ground fog in my part of town, but that cleared up before I left the city limits. I arrived for the second time at the observing site right at 5am (12UT). I had a little bit of time before I needed to start photographing the comet, so I decided to get the binoculars out and look around from the warmth of my car for a few minutes. Sticking my head out my window I could see Scorpius and the northern reaches of Centaurus, which I mostly only knew from my observing runs at Kitt Peak National Observatory near Tuscon. I scanned along the flat visible horizon (about a degree above the real horizon) with my 7x50s when I encountered a faint, large fuzzy patch less than a degree above my horizon. Omigod, omigod, omigod. Actually, that should be, "Omega, omega, omega". Omega Centauri! From 41d 19m (+/- 3m) north latitude; neat! I sketched the stars in the area to confirm this because I didn't have an atlas with me; I was able to barely see the 2.5 magnitude Zeta Centaurus naked-eye at the same altitude as Omega. I didn't even think to try to see NGC 5128.

I got in 0.5, 1, 2, and 4 minute exposures of Hale-Bopp with my 135mm f/2.8 lens, and then decided to wait 10 minutes for it to rise higher to take a few more. During this time, I studied the comet with my 7x50s and naked- eye. Unfortunately, I was looking over Laramie, which reduced my naked-eye limiting magnitude to about 5.5 in that area, and that combined with the interference from Gamma Sagittae made a naked-eye sighting of the tail difficult. However, with the binocs, I was able to trace the ion tail out to about 5-6 degrees and seeing both the ion tail and the bright dust fan was really cool, and a nice contrast to Hyakutake last year. I checked again, and Omega Centauri was gone by this time. I tried to do a magnitude estimate of Hale-Bopp, but Laramie's skyglow was creating a significant amount of differential effects and I just couldn't correct for it. I got another photo, and watched dawn break at about 12:36UT and then headed home. When I got home at 6am, it was -9F with very dense ground fog; I'm glad the fog was confined to Laramie itself!


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