Workflow - Determining the transform coefficients

1.Step

  • Make 10 images of several FOVs - see "Charts, Photo metric Parameters"
  • Name all standard stars in FOVs
  • Generate light curves for every marked star amd every filter (B-V-R-I) for example using MuniWin
  • As a result you receive the instru-mental parameters

2. Step

  • Download photo-metric tables (FOVs
  • Calculation absolute values for V B R I
  • Insert star names and differences V-C, V-K1,... according to image processing e.g. with MuniWin
  • Calculation standard star differences for different filters.

3. Step

  • For every FOV create a table with instrument data for every filter
  • Calculate average values for every star difference and filter

4. Step

  • Create a comparison table between instrument and standard star data
  • Calculate the differences between filter instrumental and standard star values

5. Step

  • Create diagrams for transformation coefficients.

Remark: 

If you use Excel and point chart, excels delivers automatically equation for transformation coefficients

6. Final Step

Transfer instrumental values into standard photo-metric values, using following equations:

dB = dv + Cb*(db - dv)    Cb = (dB - dv) / (db - dv)

dV = dv + Cv*(dv - dr)    Cv = (dV - dv) / (dv - dr)

dR = dv + Cr*(dv - dr)    Cr = (dR - dv) / (dv - dr)

dI = dv + Ci*(dv - di)    Ci = (dI - dv) / (dv - di)

 

Remark: Instead of using Excel for transformations, there is a Perl-script available - conv2std.pl - see also manual "priloha1".