rot

 function mat=rot(ra, dec)

 Return the rotation matrix to convert from a coordinate system 
 centered on a given pointing position, to a coordinate system with 
 X aligned with RA=0h, Y aligned with RA=6h, Z aligned with the NCP

 Inputs:

   ra  - The right acension, in radians

   dec - The declination, in radians

0001 function mat=rot(ra, dec)
0002 
0003 % function mat=rot(ra, dec)
0004 %
0005 % Return the rotation matrix to convert from a coordinate system
0006 % centered on a given pointing position, to a coordinate system with
0007 % X aligned with RA=0h, Y aligned with RA=6h, Z aligned with the NCP
0008 %
0009 % Inputs:
0010 %
0011 %   ra  - The right acension, in radians
0012 %
0013 %   dec - The declination, in radians
0014 
0015 
0016 cr = cos(ra);
0017 sr = sin(ra);
0018 
0019 cd = cos(dec);
0020 sd = sin(dec);
0021 
0022 rotr = [cr, -sr,  0; sr, cr, 0;   0, 0,  1];
0023 rotd = [sd,   0, cd;  0,  1, 0; -cd, 0, sd];
0024 
0025 mat = rotr*rotd;
0026 
0027 return
0028