From: Bruce Schupler 
To: atm{at}shore.net
Reply-To: Bruce Schupler 


From your description, it sounds to me like your alt-alt mount is what is
called "an XY mount with the fixed axis North/South" in the
satellite tracking community.  These used to be fairly common and provided
excellent coverage except for 2 keyholes located low in elevation in the
North and South.  The oddest thing about these mounts is the rotation of
the antenna (or telescope if you will) as the mount moves in azimuth.  If
you are high enough in elevation to be above the keyholes, the antenna will
rotate around its own central axis as the X and Y axes are driven to do a
constant azimuth scan (ie, if a point on the edge of the antenna is down
when the antenna is pointed South, it will be horizontal when pointed East,
up when pointed North, and horizontal on the other side when pointed West).

Bruce Schupler

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