Sunday, August 16, 2009

Rarer Than Hen's Teeth!

It is rare that the Summer monsoonal flow clears out to allow any astronomical observing in the 2 month period between 1 July and 31 August. And it is one of the corollaries of Murphy's Law that if it does clear, it happens during full moon or definitely on a school night. So it is rare indeed when it clears on a dark-of-the-moon Saturday with enough advance notice to make plans. This has been a rather pathetic monsoon - we are several inches behind in rainfall, this after the weathermen predicted a wetter than average season, but we really haven't had that much clear weather. Yes, the diurnal variation allows clearing usually late in the evening and most days dawn clear, but you can't depend on it.

Thursday we had a 60% chance of rain - unusually high for Tucson, so what happens? It clears out - the moisture heads east and north somewhere and dry air is overhead. I still haven't loaded up the scopes in the van after our Midwest trip (why bother - it's the rainy season!), so I got out my little tracking platform and planned some wide field imaging. I didn't even pack (I forgot, actually) the binoculars, so mostly stood and enjoyed the brilliant Milky Way while taking some pictures. No firm plans - a few objects on the list that I didn't actually get to, but I did pack the IR-modified camera to take some shots.

Heading west towards one of my favorite pullouts on the Kitt Peak National Observatory road, I arrived late and saw the last rays of twilight illuminating the 4-Meter Mayall Telescope Dome with the Teapot asterism in Sagittarius behind. In the next 15 minutes (the time between the 2 shots), the Milky way became more obvious, and the dome fainter as twilight faded. Both were taken with the Canon XSI at ISO 1600 and 15 seconds of exposure. The first was with a zoom set to 70mm and F/2.8, the second with a 50mm and F/2. In both pictures, the diffuse glow near the top is the Lagoon Nebula (M8), and the diffuse golden glow to the left and a little down is the globular cluster M22. The wider field below also contains clusters M6 and M7 at lower right.

I continued up towards the top of the mountain and took some comparison shots of the Milky Way with visible and IR cameras - will need to look at the results before posting. There are some things visible in the IR I was not expecting... It was a fun night, always great to get out under a dark sky, and I was home by 1am. We've got a star party planned for the Kitt Peak picnic area next Saturday - chances of clear sky? Iffy at best, but we'll be there to give it a try!

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