To get your mean coordinates of a particular equinox into apparent
coordinates for a particular date, you will have to make a few
calculations....
1) apply proper motion of polaris until the new date
2) precess the result to the new date
3) convert to ecliptic cordinates using the mean obliquity of the new date
4) apply nutation to the ecliptic longitude
5) apply annual aberration to the true ecliptic coordinate
5a) apply diurnal aberration and parallax (these two are generally ignored)
6) if rqd, convert back to equatorial by using the true obliquity of the
new date
Also, don't forget to use the apparent lst if converting to Declination
and HrAngle
Finally, apply refraction to the altitude if you want it in alt-azi form
Many star chart programmes miss a few of these steps, but I would check
out some of them and see if they provide the numbers you are looking for.
On 2014-11-28 23:52, James E. Morrison wrote:
I am working on two modest projects, both of which require accurate
coordinates (RA and declination) of Polaris several hundred years ago.
I have been using a spreadsheet of my own doing to calculate
precessed stellar coordinates using the formulae in Meeus, but I'm not
very confident in the results as I have only one sample giving
confirmed values. I am hoping someone in the sundial brain trust can
direct me to an available trusted source of Polaris coordinates for
years in the past. A few accurate values that I can try to replicate
would also be useful.
Best regards,
Jim
James E. Morrison
janus.astrol...@verizon.net <mailto:janus.astrol...@verizon.net>
Astrolabe web site at http://astrolabes.org
---------------------------------------------------
https://lists.uni-koeln.de/mailman/listinfo/sundial
--
---------------------------------------------------
https://lists.uni-koeln.de/mailman/listinfo/sundial
