[AZ-Observing] Happy Jack site

  • From: Brian Skiff <Brian.Skiff@xxxxxxxxxx>
  • To: az-observing@xxxxxxxxxxxxx
  • Date: Fri, 12 Mar 2004 14:55:15 -0700 (MST)

     As many of you know, Lowell Observatory is planning on building
a 4-meter telescope.  The site for the telescope is not absolutely
decided, but is very likely to be a cinder cone just west of the
settlement of Happy Jack in central Arizona.  Elevation is about
7700 feet.  Attilla Danko has kindly added a new 'ClearSkyClock'
for the location:  

http://cleardarksky.com/c/DCTOb1AZkey.html?1

     My purpose in mentioning this is that visual and imaging observers
may be interested in using the site before construction begins in earnest,
probably this time next year.  The summit is not large but should accomodate
a few groups/vehicles.  At present there is a small fenced compound
holding Lowell site-testing apparatus, with a weather-instrument mast,
small trailer, etc.
     The advantage of the site, compared to essentially all that are
used by folks on this list is plainly evident by the following:

http://www.lowell.edu/Research/NGLTbak/hj.2003.jpg

This shows a histogram of seeing measurements taken in 2003, summarizing 
387 hours of data on 99 nights.  The median seeing is 0".84 full-width-
half-maximum, and the mode (most common) value is 0".75.  The first quartile
seeing is 0".61.  This last figure means that a quarter of the time
the seeing is 0".6 _or_less_.  (The plot dies out below 0".5 because the
two-hole differential image-motion rig is on a C14, which limits 
resolution to about that of a 10-inch telescope.  The rig has been used
at the WIYN telescope on Kitt Peak, from which we know that the results
are reliable in comparison to the monitoring done with that telescope.)
     In brief, this is a good seeing as you'll find at a world-class
observatory site.  Later this spring and again all through the post-monsoon
months should be the times to check out this site.

\Brian
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