[AZ-Observing] Re: Precession Computations
- From: "Richard Harshaw" <rharshaw2@xxxxxxx>
- To: <az-observing@xxxxxxxxxxxxx>
- Date: Sat, 28 Apr 2012 12:00:04 -0700
Thanks, Tim. Just what I was looking for!
Richard Harshaw
Cave Creek, Arizona
Brilliant Sky Observatory
-----Original Message-----
From: az-observing-bounce@xxxxxxxxxxxxx
[mailto:az-observing-bounce@xxxxxxxxxxxxx] On Behalf Of Tim Jones
Sent: Saturday, April 28, 2012 9:28 AM
To: az-observing@xxxxxxxxxxxxx
Subject: [AZ-Observing] Re: Precession Computations
Rick Fisher of the National Radio Astronomy Obs in Va has an amazin resource
on his page at http://www.cv.nrao.edu/~rfisher/Ephemerides/earth_rot.html.
From the precession section -
Equations, accurate to one arcsecond, for computing precession corrections
to right ascension and declination for a given date within about 20 years of
the year 2000 are
RA = RA(2000) + (3.075 + 1.336 * sin(RA) * tan(Dec)) * y
Dec = Dec(2000) + 20.04 * cos(RA) * y
where y is the time from January 1, 2000 in fractional years, and the
offsets in RA and Dec are in seconds of time and arcseconds, respectively.
Very accurate telescope pointing calculations should use the exact equations
given on pages 104 and 105 of ref [1].
HTH,
Tim
On Apr 28, 2012, at 7:39 AM, Richard Harshaw wrote:
> Does anyone in this august group know the formula, transformation or
algorithm to determine the vectors for precession for any point on the sky
using equatorial coordinates and a given date?
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