Oooh - A Close Miss!

As I mentioned in my last post, there was to be a sunset alignment with Kitt Peak National Observatory from "Bad Dog" Overlook (actually Babad Do'ag - Frog Mountain in the native tongue).  So I was joined by 2 of my local Tucson readers to observe it.  It was a spectacular afternoon, very clear sky, though a brisk breeze out of the east was going to play havoc with shaking long focal length telescopes...  At left is the view shooting almost directly up-sun with the zoom lens set to about 70mm, distant mountains Baboquivari on the left, and the flat-topped Kitt Peak on the right side of the view.  The Catalina Highway, used to access the mountain, is the diagonal road across the bottom of the frame.  At right, a mesquite tree and yucca line a ridge about  a half mile or mile away to the north.

After getting set up for imaging, I visited some with Jim and Dick who also came up to observe the sunset.  Each of them brought gear - Jim an H-alpha telescope, Dick a little refractor with white-light solar filter.  As soon as the sun touched the horizon, I knew it was a little too far to the north.  It never touched the solar telescopes that make up the left side of the Observatory profile.  Oh well, these things happen!  Looking at these images, calculations indicate that the sun should be about 6 arcminutes further south, or a declination of about -20.895 degrees.  Like I warned in the previous post, unfortunately, the sun moves about 12 arcminutes/day this time of year, so you've got to be lucky for a perfect alignment this far from Solstice!  By the way, you can look closely and see some nice sunspot groups on the suns face.  While atmospheric refraction gives the upper edge a greenish/blue rim and the lower edge red (another recent post!) interestingly the sunspots have the lower edges green and the upper edges red!  When you pause and think about it, the explanation is pretty simple - the lower edge of a sunspot is actually the upper edge of the bright edge of the sunspot, so has a green upper edge like the top of the disk. 

 

The thin haze or smog shown in the up-sun picture above had a surprise waiting for us after sunset.  Once the sun disappeared below the horizon, it made a perfect screen to see shadows cast from the domes and mountains!  I don't think I've ever seen an effect this strongly before.  With the contrast stretched just a little, you can see each mountaintop structure very clearly casting a shadow.   These are officially called crepuscular rays, and are often seen by casual observers, mostly around sunrise and sunset.  They tend to fade fast, but even after a few minutes, they were still visible after switching to the hand-held zoom lens for a wider exposure.  One is even faintly seen from a peak far to the left side of the picture.  It was really cool to see.

Ok, I'm officially done with these Kitt Peak sunsets for the season - I promise not to submit any more till the end of the year - I promise!