EULER
Name
EULER
Purpose
Transform between Galactic, celestial, and ecliptic coordinates.
Explanation
Use the procedure ASTRO to use this routine interactively
Calling Sequence
EULER, AI, BI, AO, BO, [ SELECT, /FK4, /RADIAN, SELECT = ]
Inputs
AI - Input Longitude, scalar or vector. In DEGREES unless /RADIAN
is set. If only two parameters are supplied, then AI and BI
will be modified to contain the output longitude and latitude.
BI - Input Latitude in DEGREES
Optional Input
SELECT - Integer (1-6) specifying type of coordinate transformation.
SELECT From To | SELECT From To
1 RA-Dec (2000) Galactic | 4 Ecliptic RA-Dec
2 Galactic RA-DEC | 5 Ecliptic Galactic
3 RA-Dec Ecliptic | 6 Galactic Ecliptic
If not supplied as a parameter or keyword, then EULER will prompt for
the value of SELECT
Celestial coordinates (RA, Dec) should be given in equinox J2000
unless the /FK4 keyword is set.
Outputs
AO - Output Longitude in DEGREES, always double precision
BO - Output Latitude in DEGREES, always double precision
Optional Input Keyword
/FK4 - If this keyword is set and non-zero, then input and output
celestial and ecliptic coordinates should be given in equinox
B1950.
/RADIAN - if set, then all input and output angles are in radians rather
than degrees.
SELECT - The coordinate conversion integer (1-6) may alternatively be
specified as a keyword
Example
Find the Galactic coordinates of Cyg X-1 (ra=299.590315, dec=35.201604)
IDL> ra = 299.590315d
IDL> dec = 35.201604d
IDL> euler,ra,dec,glong,glat,1 & print,glong,glat
71.334990, 3.0668335
Revision History
Written W. Landsman, February 1987
Adapted from Fortran by Daryl Yentis NRL
Made J2000 the default, added /FK4 keyword W. Landsman December 1998
Add option to specify SELECT as a keyword W. Landsman March 2003
Use less virtual memory for large input arrays W. Landsman June 2008
Added /RADIAN input keyword W. Landsman Sep 2008