Celestia Forums

Hi (: I'm in desperate need of some help with some calculations.
1st, I need to convert ecliptic coordinates (-39 +/- 9 microas/yr toward the East and 31 +/- 8 microas/yr toward the North) to equatorial.
2nd, I need rotation matrices for the galactic plane in relation to the equatorial, and for the supergalactic plane in relation to the galactic and equatorial, and maybe an algorithm to convert between the three as well.
Other problems might arise later, too. Could you please help me out?

egasimus wrote:Hi (: I'm in desperate need of some help with some calculations.
1st, I need to convert ecliptic coordinates (-39 +/- 9 microas/yr toward the East and 31 +/- 8 microas/yr toward the North) to equatorial.

From Astronomical Algorithms (Meeus):
tan A = (sin L cos E - tan B sin E) / cos L
sin D = sin B cos E + cos B sin E sin L

A: right ascension
D: declination
L: ecliptical longitude
B: ecliptical latitude
E: Obliquity of the ecliptic (angle between ecliptic and celestial equator, or axial tilt of the Earth)

NOTES:
* The original formulae used Greek letters, substituted for convenience.
* for the tan A formula, I recommend using the second arctan function (atan2) because this avoids issues with division by zero.

Yeah, but what about them being in microarcseconds? Do I convert them to degrees first?

If it's got trig formulae, use radians.