Sunday, December 16, 2012

Las Cienegas observing

With all the excitement regarding the close pass of Asteroid 4179 Toutatis (see the previous post), I neglected to share that the night before I made the trek to the Las Cienegas National Conservation Area to do some dark sky observing.  For many years, the Tucson Amateur Astronomy Association utilized an old airstrip within Las Cienegas as a dark sky site for monthly club star parties.  Despite being about 45 minutes from the east side of Tucson, the skies are quite dark, and it is my experience that the naked eye limiting magnitude at zenith can approach 7.0.  It is much darker than the clubs site west of town at TIMPA.  Over the last few years the TAAA has discontinued use of the site for regular star parties due to the acquisition and development of a club owned dark site about about 2 hours from town.  In addition, many members are uncomfortable driving down the sometimes rutted dirt road that leads to the old airstrip.

As mentioned, the site is about 45 minutes from Tucson, and from my house I can arrive in about 60-70 minutes.  This affords me the ability to work all day and then head to the site in time for darkness.  Last Monday night I made such a trip, joining my good fiends Jerry and Bill for several hours of dark skies, conversation, and of course observing.  Recently, we have identified a very nice spot in Las Cienegas to set up our telescopes, that is only about 5 minutes drive from the entrance.  The spot is in a slight depression in the rolling grasslands, which does seem to affect the temperatures, with cooler air settling in more quickly.  During our session temperatures were balmy, in the mid-20's, about 15-20 degrees colder than back at home.

Below is a 20 second exposure of Orion rising in the east.  The yellow glow on the horizon is the light dome from Fort Huachuca.  Despite how bright it seems in the image, the skies are still markedly darker than in Tucson as evidenced by the winter milky way extending down left of Orion.  Click the image to enlarge it.

I had decided to make the trip very lightweight and brought along an alt-az mount for the TEC 140.  I spent quite a bit of time panning through the milky way from Cassiopeia eastward.  This is the less bright region of the milky way in our sky, as we are peering away from the center of our galaxy.  I chose this area due to the simple fact that the summer milky way from Cassiopeia westward is where I have spent the last several months observing.  The skies were quite cooperative and I enjoyed my first extended views of objects such as the various nebulas in Orion (M42, M43, the Flame, The Running Man, etc).  One of the great things about a refractor are the beautiful low power wide field views one can achieve.  I was truly lost among all the open clusters in Cassiopeia, as every nudge of the telescope seemed to bring another into view.  At times, I would wonder what NGC cluster I was looking at, but before I could get up and go consult a chart I would again lose myself in the sheer aesthetics of the view through the eyepiece.

We had a great compliment of telescopes for the evening, with a 63mm Zeiss refractor, my 140mm TEC refractor, and a 9.25 inch SCT.   If you know Bill, it will not surprise you to hear that he was able to spot the same 14th and 15th magnitude Arp Galaxies in his 63mm Zeiss as we could observe in Jerry's 9.25 SCT.  Certainly there were no galactic details to be seen in the Zeiss, but the fact that we could detect the small, faint glow at all says something about the quality of the telescope and the transparency of the skies.  And yes, I said "we could detect," as I also observed some of them in Bill's telescope.

This has been a fairly long winded post for a Sunday morning, but if you are reading it and are a Tucson based amateur astronomer, I would strongly suggest that you consider the Las Cienegas area as a nearby location.  It's ease of access and reasonably dark skies make it quite enjoyable.

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