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Making a plot in equatorial coordinates
Hi,
I have a list of objects given in equatorial coordinates... Is there a programm which lets me plot a projection of these coordinates (like you would print out a map of the world) with my datapoints in it? Greetings, Christian Herenz |
#2
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Making a plot in equatorial coordinates
On Fri, 26 Jun 2009, Christian Herenz wrote:
I have a list of objects given in equatorial coordinates... Is there a programm which lets me plot a projection of these coordinates (like you would print out a map of the world) with my datapoints in it? I use SkyMap, but it isn't free, and of course you need to do a little work to prepare the data and define it to SkyMap. Eric |
#3
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Making a plot in equatorial coordinates
On Jun 26, 6:03 pm, Christian Herenz
wrote: Hi, I have a list of objects given in equatorial coordinates... Is there a programm which lets me plot a projection of these coordinates (like you would print out a map of the world) with my datapoints in it? Greetings, Christian Herenz Below is a Perl subroutine to convert a series of (RA, Dec) values into a Hammer-Aitoff projection. The resulting (x, y) values can then be plotted with any ordinary graphics package to show the projected locations. ################################################## ################## # Given (RA, Dec), convert to (x, y) in Hammer-Aitoff projection # # The two arguments are RA and Dec in decimal degrees, # and we return a two-element list for x, y. # We scale (x, y) so that they range from # # 0 x 360 # -90 y 90 # # so that labels will correspond to (RA, Dec) in decimal degrees. # # MWR 7/22/2006 sub convert_radec_to_hammeraitoff { my($ra, $dec); my($tra, $tdec); my($x, $y, $z); my($DEGTORAD); my($pi); $ra = $_[0]; $dec = $_[1]; $pi = 3.14159; $DEGTORAD = $pi/180.0; # convert RA and Dec into radians $tra = ($ra*$DEGTORAD) - $pi; $tdec = ($dec*$DEGTORAD); # calc auxiliary variable z $z = sqrt( 1.0 + cos($tdec)*cos($tra/2.0) ); # calc Hammer-Aitoff normalized coords (x, y) $x = ( cos($tdec)*sin($tra/2.0) ) / $z; $y = sin($tdec) / $z; # now scale the normalized coords so that X ranges over 0 to 360, # and y ranges over -90 to +90. $x = ($x*180.0) + 180.0; $y *= 90.0; return($x, $y); } |
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