Questions

Edward S Light (light@argoscomp.com)
Wed, 27 Oct 1999 12:10:44 -0400 (EDT)

With the Christmas gift season rapidly approaching, several questions
have come to mind and it seems to me that the collective List members
most likely have the answers.

1) GPS-derived positions

   I recall that, at least a few years ago, coordinates obtained from
   the GPS system were intentionally degraded (I believe the term was
   "SA"). If this is still true, what is the approximate magnitude of
   the effect? Centimeters? Meters?  Worse? One frequently sees GPS-
   derived positions quoted to 0.000 001 degrees, which is approximately
   0.11 meters (or about 4 inches), and I wonder about the meaningful-
   ness of all those significant digits. (My own coordinates, quoted
   in my signature, are given to the nearest 11 meters and were based
   on measuring a paper USGS 1:24000 map to the nearest 0.005 inch and
   assuming absolutely no errors in the production of that map.)

2) "Go-to" telescopes

   With the current ever-expanding crop of computerized "go-to"
   telescopes (e.g. the Meade 90mm and 125mm ETXs, the larger Meade
   LX-200s, and the Celestron equivalents), I understand that one
   can "ask" these instruments to point to a specified RA/Dec in
   the sky. Can one specify altitude and azimuth?

   If one must input RA/Dec, is it assumed they are Equator-Equinox-
   of Date? Or 2000? (I know - not much difference between them these
   days, but I like to plan ahead :)  .)


To minimize List-clutter responders are encouraged to reply by private
e-mail. Thanks in advance for any information.


Clear and dark skies!
   Ed Light

Lakewood, NJ, USA
N 40.1072, W 074.2317, Hgt +21 m (69 ft)

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