天图投影上的圆

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  • On the atioff projection map, how to draw a circle (e.g. telescope field of view)? suppose, telescope pointed at (Ra0,Dec0), FOV is a circle with radius R0
  1. Change the coordinate system from celestial to the designed coordinate (pole at Ra0,Dec0).
  2. Then the circle in the new coordinate system is simply DecP=90-R0
  3. change the new coordinate system back to celestial
  • IDL code(在天球投影上画出一个中心在Ra，Dec，半径为2.5度的圆）
Rad=2.5
fRa=indgen(360)*1.
fDec=fRa*0+90-Rad
change_cor,fRa0,fDec0,fRa,fDec,Ra,Dec,0,2 ;my own code文件:Change cor.pro.txt
aitoff,fRa0,fDec0,x,y
aitoff_grid,60,/label
cgplots,x,y,psym=3,color='red'
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