MBCAA Observatory

Transformation coefficients: B, V measurements

Observed: 5 Jan 2005, 24 Dec 2006, 12 Jan, 9, 15, 20 Feb, 11, 14 March, 24 Apr 2007

M. Bonnardeau
28 May 2007

Abstract

The transformation coefficients for my telescope and camera and B,V filters are measured.

Introduction

For an introduction to transformation equations and coefficients for differential photometry, see HERE.

The transformation coefficients for my telescope and camera and B,V filters are derived by multiple observations of Landolt's fields (1992, VizieR II/183A), spanning over several nights. The stability of these coefficients can then be assessed.

Observations

Run Session FieldNb of
subfields
Nb of
stars
B-V
range
TbvCbv TbCbTv Cv
0 20050107 L95 3 13 1.852 1.008 +0.012 +0.008 +0.024 -0.010 +0.021
1 20061224 L98 1 8 1.121 1.075 -0.054 0.042 -0.050 -0.026 -0.002
220070112L95 2 9 1.208 1.017 -0.027 0.008 -0.010 -0.007 0.017
320070209L95 2 9 0.640 1.006 -0.022 -0.021 0.013 -0.040 0.049
420070215L95 2 9 0.640 1.057 -0.059 0.023 -0.032 -0.037 0.026
520070215L104 1 7 0.775 1.091 0.003 -0.008 0.032 -0.052 0.007
620070220L98 1 7 1.121 1.031 -0.023 0.010 -0.020 -0.018 0.000
720070311L98 1 8 1.121 1.017 -0.010 -0.024 -0.000 -0.035 0.005
820070314L98 1 8 1.121 1.031 -0.029 0.018 -0.032 -0.014 -0.002
920070424L104 1 5 0.811 0.918 0.046 0.052 -0.072 +0.093 -0.099
1020070424L101 1 5 0.584 0.903 0.142 -0.124 0.193 0.006 0.009
1120070424 PG1323 1 4 0.847 0.998 -0.001 0.023 -0.012 -0.004 0.002

The transformed magnitudes B,V are calculated the following way:

B = b+Tb*Tbv*[(b-v)-(Bc-Vc)]
V = B-[(Bc-Vc)+Tbv*[(b-v)-(Bc-Vc)]]

or

V = v+Tv*Tbv*[(b-v)-(Bc-Vc)]
B = V+[(Bc-Vc)+Tbv*[(b-v)-(Bc-Vc)]]

with Bc,Vc the magnitudes of the comparison star, b,v the measured magnitudes of the star being studied. The only coefficients that are then useful for the equations are Tbv, Tb*Tbv, Tv*Tbv:





The coefficients are fairly stable. The worst is for run 10 but this is also the run with the smallest B-V range (the larger this range, the better the coefficient determination is).
The average values and standard deviations are:

Tbv = 1.013 +/- 0.056
Tb*Tbv = 0.002 +/- 0.042
Tv*Tbv = -0.014 +/- 0.036

Technical notes

Telescope and camera configuration.

Computer and software configuration.



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