Star sizes on DSS images
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.
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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
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