Saturday, November 14, 2015

"Bad Dog" Sunset

It was such a lovely afternoon yesterday, and with Melinda feeling a little better every day since she is skipping the chemo this month, we battled rush-hour traffic for an evening drive! I had seen on some planetarium software that the post-sunset skinny crescent moon would be low in the southwest somewhere near the silhouette of Kitt Peak, so we headed east towards one of our favorite outlooks, "Bad Dog" (in actuality, Babad Do'ag - the native name of the mountain range north of town, "Frog Mountain"). Similar to "A" Mountain, it is paved to a nice parking lot a few hundred feet above the local elevation, though instead of overlooking the downtown Tucson skyline, you have a panorama view of the entire Tucson valley from the south to the west.

Traffic was bad enough that we missed the sunset, though we watched the last golden rays disappear on the peaks and witnessed the Belt of Venus rising as we sped down Tanque Verde. Missing the sunset was ok, almost expected, and we arrived pretty far into twilight. The views are such that almost anything you take pictures with comes out great, so had brought a number of lenses from the TEC 140 to the kit lenses for the camera. Since the former was longer to set up, I did it first and captured Kitt Peak against the twilight. First thing I noticed was that the seeing was quite poor. Granted we were looking through 60 miles of atmosphere, the stiff surface breezes were doing a number on the image sharpness.

Undeterred, I went on - setting up another scope, the smaller Meade 80mm, which at F/6 has less than half the focal length of the TEC scope, and corresponding wider field. And to make things more interesting, I shot some images with a vertical format, shifting between them to make a panorama. Shown at left, this is the result of cropping somewhat from the panorama made from 7 individual frames. Of course, I could have shot it with a single 180mm lens or so, but I like having the higher resolution the longer focal length provides, though the blog limit of 1600 pixels puts a crimp on displaying the full resolution images. Granted, with the poor seeing, a single exposure with shorter lens wouldn't have been a bad idea... More on that below...

Next up, since the TEC was still set up but the lighting behind Kitt Peak was dimming, I took a series of shots of the "Tucson skyline", such as it is. This is built up from 3 exposures of 4 seconds duration each and shows the University of Arizona area, from the Arizona Stadium at left to Aloft Hotel at right a half mile to the north. From Babad Do'ag, it just happens to lie on the same path as Tucson's downtown area, then up beyond that you can see housings up what I suspect is the Star Pass area up west into the Tucson Mountains. There were some lights on in the stadium for preparations for a game today, and also there was an NCAA Soccer match on the field to the south, thus all the lights. There also appear to be other lighting centers on campus, and I'm thinking it might have been a pep rally for today's football game.

Finally, as it got a little darker, the crescent moon sank low enough to get it into a picture with a normal camera lens. So here I can make the comparison between a single wide shot or panorama from several shots. At left is a single shot with my kit lens for the Canon XSi, set to 60mm focal length. At right is a 4-frame panorama with the same lens set to 70mm, and combined with Photoshop. Unfortunately, with the blog's 1600 pixel-wide limit, you can't really tell the difference between them, so these likely look pretty identical. Certainly with the original files, the panorama was 8500 pixels wide and the single shot only 4500, so the panorama should be sharper, all things being equal!

Even when you go to the full-camera-resolution, the difference is hard to see, but perhaps detectable. At left is the cropped image at Kitt Peak both from the panorama and single shot with no subsequent processing. Since the panorama was taken at a little longer focal length on the zoom (70mm vs 60mm), the image looks larger. Also, the single exposure was a 4 second exposure at F/5.6, while the panorama was taken for 10 seconds at F/7.1, pretty much equivalent. Looking at the 4-meter and 90" telescope profiles on the right side of Kitt Peak (the flat-topped mountain), I think the longer focal length helps pull out a little more resolution. If more exposures at longer focal length were taken I think the difference would be more visible...

We didn't wait for moon set - it would have been against a black horizon anyway, so packed up and headed home, stopping at Pinnacle Peak for a steak dinner on the way. A fun evening and a chance to get out of the house!

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