pro glactc,ra,dec,year,gl,gb,j, degree=degree, fk4 = fk4, $ SuperGalactic = superGalactic ;+ ; NAME: ; GLACTC ; PURPOSE: ; Convert between celestial and Galactic (or Supergalactic) coordinates. ; EXPLANATION: ; Program to convert right ascension (ra) and declination (dec) to ; Galactic longitude (gl) and latitude (gb) (j=1) or vice versa (j=2). ; ; CALLING SEQUENCE: ; GLACTC, ra, dec, year, gl, gb, j, [ /DEGREE, /FK4, /SuperGalactic ] ; ; INPUT PARAMETERS: ; year equinox of ra and dec, scalar (input) ; j direction of conversion (input) ; 1: ra,dec --> gl,gb ; 2: gl,gb --> ra,dec ; ; INPUTS OR OUTPUT PARAMETERS: ( depending on argument J ) ; ra Right ascension, hours (or degrees if /DEGREES is set), ; scalar or vector ; dec Declination, degrees,scalar or vector ; gl Galactic longitude, degrees, scalar or vector ; gb Galactic latitude, degrees, scalar or vector ; ; All results forced double precision floating. ; ; OPTIONAL INPUT KEYWORD PARAMETERS: ; /DEGREE - If set, then the RA parameter (both input and output) is ; given in degrees rather than hours. ; /FK4 - If set, then the celestial (RA, Dec) coordinates are assumed ; to be input/output in the FK4 system. By default, coordinates ; are assumed to be in the FK5 system. For B1950 coordinates, ; set the /FK4 keyword *and* set the year to 1950. ; /SuperGalactic - If set, the GLACTC returns SuperGalactic coordinates ; as defined by deVaucouleurs et al. (1976) to account for the ; local supercluster. The North pole in SuperGalactic coordinates ; has Galactic coordinates l = 47.47, b = 6.32, and the origin is ; at Galactic coordinates l = 137.37, b= 0 ; ; EXAMPLES: ; Find the Galactic coordinates of Altair (RA (J2000): 19 50 47 ; Dec (J2000): 08 52 06) ; ; IDL> glactc, ten(19,50,47),ten(8,52,6),2000,gl,gb,1 ; ==> gl = 47.74, gb = -8.91 ; ; PROCEDURE CALLS: ; BPRECESS, JPRECESS, PRECESS ; HISTORY: ; FORTRAN subroutine by T. A. Nagy, 21-MAR-78. ; Conversion to IDL, R. S. Hill, STX, 19-OCT-87. ; Modified to handle vector input, E. P. Smith, GSFC, 14-OCT-94 ; Converted to IDL V5.0 W. Landsman September 1997 ; Added DEGREE keyword, C. Markwardt, Nov 1999 ; Major rewrite, default now FK5 coordinates, added /FK4 keyword ; use external precession routines W. Landsman April 2002 ; Add /Supergalactic keyword W. Landsman September 2002 ; Fix major bug when year not 2000 and /FK4 not set W. Landsman July 2003 ;- On_error,2 compile_opt idl2 if N_params() lt 6 then begin print,'Syntax - glactc, ra, dec, year, gl, gb, j, [/DEGREE, /FK4]' print,'j = 1: ra,dec --> gl,gb j = 2: gl,gb -->ra,dec' return endif radeg = 180.0d/!DPI ; ; Galactic pole at ra 12 hrs 49 mins, dec 27.4 deg, equinox B1950.0 ; position angle from Galactic center to equatorial pole = 123 degs. if keyword_set(SuperGalactic) then begin rapol = 283.18940711d/15.0d & decpol = 15.64407736d dlon = 26.73153707 endif else begin rapol = 12.0d0 + 49.0d0/60.0d0 decpol = 27.4d0 dlon = 123.0d0 endelse sdp = sin(decpol/radeg) cdp = sqrt(1.0d0-sdp*sdp) radhrs=radeg/15.0d0 ; ; Branch to required type of conversion. Convert coordinates to B1950 as ; necessary case j of 1: begin if ~keyword_set(degree) then ras = ra*15.0d else ras =ra decs = dec if ~keyword_set(fk4) then begin if year NE 2000 then precess,ras,decs,year,2000 bprecess,ras,decs,ra2,dec2 ras = ra2 decs = dec2 endif else if year NE 1950 then precess,ras,decs,year,1950,/fk4 ras = ras/radeg - rapol/radhrs sdec = sin(decs/radeg) cdec = sqrt(1.0d0-sdec*sdec) sgb = sdec*sdp + cdec*cdp*cos(ras) gb = radeg * asin(sgb) cgb = sqrt(1.0d0-sgb*sgb) sine = cdec * sin(ras) / cgb cose = (sdec-sdp*sgb) / (cdp*cgb) gl = dlon - radeg*atan(sine,cose) ltzero=where(gl lt 0.0, Nltzero) if Nltzero ge 1 then gl[ltzero]=gl[ltzero]+360.0d0 return end 2: begin sgb = sin(gb/radeg) cgb = sqrt(1.0d0-sgb*sgb) sdec = sgb*sdp + cgb*cdp*cos((dlon-gl)/radeg) dec = radeg * asin(sdec) cdec = sqrt(1.0d0-sdec*sdec) sinf = cgb * sin((dlon-gl)/radeg) / cdec cosf = (sgb-sdp*sdec) / (cdp*cdec) ra = rapol + radhrs*atan(sinf,cosf) ra = ra*15.0d if ~keyword_set(fk4) then begin ras = ra & decs = dec jprecess,ras,decs,ra,dec if year NE 2000 then precess,ra,dec,2000,year endif else if year NE 1950 then begin precess,ra,dec,1950,year,/fk4 endif gt36 = where(ra gt 360.0, Ngt36) if Ngt36 ge 1 then ra[gt36] = ra[gt36] - 360.0d0 if ~keyword_set(degree) then ra = ra / 15.0D0 return end endcase end