Sunday, June 20, 2010

Another McNaught Trip up Mt Lemmon

Last night (a Saturday), with a bright quarter moon setting about 1am and Melinda at work, I decided to head north of Tucson again to try imaging Comet McNaught (2009R1) again. I got it acceptably well last weekend, but the comet is supposed to be brightening as it approaches the sun, and it might look a little different... Unfortunately, as it approaches the sun, it continues to dive towards the horizon, so will be lower and not available as long as last weekend.

Like last trip, I left home about midnight for the 1 hour drive to San Pedro Vista, 17 miles up the hill and just over 7,000 feet elevation. This trip I used the 14" Celestron with the Hyperstar optics, so it was equivalent to a 700mm lens working at F/1.9. Even working in the dark, it was straightforward to set up, and I was ready to shoot by 2am.

With time to spare, and the Milky Way blazing overhead, I needed some alternate targets. I started out shooting one of my favorite objects to show at dark-sky star parties, Barnard 86, a dark nebula in Sagittarius. While a dark cloud of dust and gas may not sound very spectacular, just being able to spot it against the glowing star clouds of the Milky Way is indeed very neat. B86 is easily spotted just above the spout of the teapot asterism, located between a small star cluster (NGC 6520) and a bright star. It shows up well on images too, though is smaller than imagined after spotting it visually so many times. This image is from 10 stacked 45 second exposures, so about 7 minutes total exposure with the Canon XSi.

I also shot some more frames of the Iris Nebula, but the focus was a little off, so won't embarrass myself here!

Finally, right at 3am the comet was spotted just above Capella (Alpha Auriga) on the northeastern horizon. The sky was a little murkier than last weekend, and the comet, if anything, was less impressive than last week - perhaps because of it's lower altitude. In any case, I shot a few frames of it. Generally, it looked very similar to last weekend, a long blue ion tail and a short stubby dust tail. The comet is almost north of the sun, so generally the ion tail is swinging around slowly to the north. Compare this picture to the post last weekend(link above) - both have north up and west to the right... This image is from a series of 45 second exposures that were then stacked using the comet head as reference, so that the stars appear as trailed. After a dozen frames, morning twilight started, and I began to take down the scope. For dessert, the sky presented me with a glimpse of the Pleiades rising in the brightening eastern sky.

There was some talk of the comet being visible in the northwest after sunset, but I don't believe it will be worth writing home about - small and very low in the sky. So this is likely my last attempt to chase it down...

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