I needed a way to scale circle size to approximate magnitudes. Here is
how I did it.
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Relation between star V magnitude and radius in arcseconds on DSS images. Data were taken from 3 different DSS fields. |
A rough relatio to predict star sizes in arcsec based on V mag (for DSS) Work done in: /home/sco/work_2017/n6946_R/T1/n7790/S Usage: usno_look 08:13:15.10 +45:59:29.0 5.0 15.0 1 JustText arg1 - Ra J2000 in sexigecimal arg2 - Dec J2000 in sexigecimal arg3 - search Radius in arcmin arg4 - faint V magnitude limit arg5 - ds9 frame to display in arg6 - overplot code (S,G,SG,JustText,magR2,V) NGC7790 23:58:24.0 +61:12:30.0 To get a map: usno_look 23:58:24.0 +61:12:30.0 8.0 18.0 1 V % image_ps dss.fits 1.00800073 0.00000957 B.reg = regions saved in image units To get blue stars where I have sized the circles stored in keep_1 % ds9regget.sh B.reg circle blue 690.19 73.84 3.19 circle blue {2;17.80}..................... 624.56 24.56 3.30 circle blue {7;17.00}..................... 858.38 248.49 3.65 circle blue {71;16.70}.................... 851.59 221.61 2.99 circle blue {72;17.91}.................... 829.25 243.86 3.20 circle blue {80;16.72}.................... 801.49 235.79 5.54 circle blue {99;14.37}.................... 634.33 418.30 5.41 circle blue {219;12.83}................... 583.89 414.87 5.31 circle blue {262;13.69}................... 580.80 497.30 8.52 circle blue {875;9.62}.................... 427.28 567.28 3.61 circle blue {1017;16.63}.................. 275.70 698.96 3.40 circle blue {1143;17.72}.................. To get brighter stars (and fainter) 76 00:20:05.20 +48:51:55.00 2000.00 +00.005 -00.017 6.52 1561 # A0V s BD+48 79 RV -00 usno_look 00:20:05.20 +48:51:55.00 5.0 15.0 1 V Stored in keep_2 % ds9regget.sh B.reg circle blue 550.60 225.15 3.82 circle blue {1;14.59}..................... 422.74 200.64 4.02 circle blue {5;14.41}..................... 354.87 391.52 4.55 circle blue {7;13.90}..................... 192.92 138.85 6.15 circle blue {21;11.17}.................... 88.92 170.21 5.31 circle blue {28;12.15}.................... 298.00 298.77 17.08 circle blue {0;6.52}...................... To get fainter stars % usno_look 08:30:0.00 +48:00:00.0 5.0 20.0 1 V put in keep_3 % ds9regget.sh B.reg circle blue 218.02 73.49 1.99 circle blue {49;19.70}.................... 481.21 302.36 5.91 circle blue {78;15.98}.................... 421.00 404.50 1.94 circle blue {85;19.71}.................... 296.67 307.83 1.84 circle blue {98;19.89}.................... 216.49 340.10 3.21 circle blue {108;18.75}................... 143.48 463.97 2.91 circle blue {113;18.82}................... 99.66 498.17 3.37 circle blue {116;19.20}................... 91.33 430.76 6.60 circle blue {117;13.67}................... ++++++++++++++++++++++++ So, I make file manually: # data 690.19 73.84 3.19 circle blue 17.80 624.56 24.56 3.30 circle blue 17.00 858.38 248.49 3.65 circle blue 16.70 851.59 221.61 2.99 circle blue 17.91 829.25 243.86 3.20 circle blue 16.72 801.49 235.79 5.54 circle blue 14.37 634.33 418.30 5.41 circle blue 12.83 583.89 414.87 5.31 circle blue 13.69 580.80 497.30 8.52 circle blue 9.62 427.28 567.28 3.61 circle blue 16.63 275.70 698.96 3.40 circle blue 17.72 550.60 225.15 3.82 circle blue 14.59 422.74 200.64 4.02 circle blue 14.41 354.87 391.52 4.55 circle blue 13.90 192.92 138.85 6.15 circle blue 11.17 88.92 170.21 5.31 circle blue 12.15 298.00 298.77 17.08 circle blue 6.52 218.02 73.49 1.99 circle blue 19.70 481.21 302.36 5.91 circle blue 15.98 421.00 404.50 1.94 circle blue 19.71 296.67 307.83 1.84 circle blue 19.89 216.49 340.10 3.21 circle blue 18.75 143.48 463.97 2.91 circle blue 18.82 99.66 498.17 3.37 circle blue 19.20 91.33 430.76 6.60 circle blue 13.67 I put this into: Table1.dat I want to plot col 6 on X col 3 on Y % xyplotter_prep Table1.dat 1 To fit the data: % curve_runner 1 I fit a parabola (poly3) My plot is: Fit1.png The coefficents are: % cat poly3.out 0.32194332123E+02 0.30000000000E+01 a1 -0.30936033726E+01 0.30000000000E+01 a2 0.81455871463E-01 0.30000000000E+01 a3 Rad = a1 + a2*V + a3*V^2