[Kstars-devel] kdeedu/kstars/kstars

[Pablo de Vicente]

CVS commit by pvicente: 

Fixed a bug first pointed out by Mikhail Zotov in a private communication,
who noticed that precession between B1950 to J2000 as done by KStars does not
coincide with the results given by SIMBAD (http://simbad.u-strasbg.fr/sim-fidl.pl).
M. Zotov has not opened yet a bug in bugs.kde.org, so I have no bug
number to refer to in this commit.

  The bug comes from the fact that conversion between coordinates in B1950
to J2000 (and viceversa) involves changing from (old) catalog FK4 to FK5,
and a simple precesion, as done by KStars is not enough.

  To fix this bug I have used the following reference:
Smith, C. A.; Kaplan, G. H.; Hughes, J. A.; Seidelmann, P. K.; Yallop,
B. D.; Hohenkerk, C. Y.
Astronomical Journal, vol. 97, Jan. 1989, p. 265-279

The conversion between the FK4 catalog and the FK5 catalog requires 4 steps:
- Drop E-Terms in B1950 coordinates. In the past, the mean places of
  stars published in the FK4 catalog included the contribution to the
  aberration due to the ellipticity of the orbit of the Earth. These terms,
  known as E-terms were almost constant, and in the newer FK5 catalog they
  are not included.
- Precess from B1950 to 1984, January 1st, at 0h, using the parameters
  given by the Astronomische Rechen-Institut.
- Apply the zero-point correction to the right ascensions to correct for the
  equinox error of the FK4. This is done for 1984, Jan 1st, at 0h.
- Precess from 1984 Jan 1st at 0h, to J2000 using the new precessional
  parameters.

This bug may seem not important since KStars produced (before this patch) 
a result which is almost correct, but since the conversion between B1950 
and J2000 is done very frequently among astronomers it needs to be corrected. 

Jason Harris has told me to go on with this commit since HEAD is opened again 
for these kind of fixes.

CCMAIL: kstars-devel at kde.org


  M +2 -0      dms.h   1.13
  M +32 -0     ksnumbers.cpp   1.5
  M +11 -3     ksnumbers.h   1.8
  M +195 -49   skypoint.cpp   1.17
  M +51 -0     skypoint.h   1.16