Thanks for the information about the site's seeing Brian. Not shown in the histogram is the seasonal variation. Are there known trends in seeing quality throughout the year at established sites up your way? Back when I was imaging with my 13" and ST-7 setup in Tempe, "good" seeing was a bit below 2 arcseconds, and typical nights ranged from 2" to 3". Just based on visual observations of planets, I haven't found our popular desert sites to be any better than my backyard. As Brian has said so often, setting up on a small rise pays off. Unfortunately, we get often into problems with space, access, and wind. Folks might be interested in how the Happy Jack seeing measurements were made with very simple, off-the-shelf hardware. They use a differential image motion monitor (DIMM). Typically, an SCT with twin aperture stops (one with a prism to offset the image) sends the twin images of a bright star through two separate light paths. Then the _relative_ motion of the two star images is measured to determine the seeing. The setup works remarkably well even when wind is buffeting the poorly mounted scope, since only the relative location of the two images is required. There's a good explanation and illustration at: http://www.astro.washington.edu/rest/dimm/dimmtext.htm I saw this one in action at Apache Point Observatory. Tom -- See message header for info on list archives or unsubscribing, and please send personal replies to the author, not the list.