Transformation coefficients (with weights): B, V measurements
Observed: 5 Jan 2005, 24 Dec 2006, 12 Jan, 9, 15, 20 Feb, 11, 14 March, 24 Apr 2007
Michel Bonnardeau
29 Sept 2007
Abstract
The transformation coefficients for my telescope and camera and B,V filters are measured and computed from weighted averages and weighted standard deviations.
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 | Field | Nb of subfields |
Nb of stars |
B-V range |
Tbv | Tb | Tv | |||
| value | error | value | error | value | error | ||||||
| 0 | 20050107 | L95 | 3 | 13 | 1.852 | 1.008 | 0.029 | +0.008 | 0.006 | -0.010 | 0.021 |
| 1 | 20061224 | L98 | 1 | 8 | 1.121 | 1.075 | 0.010 | 0.042 | 0.002 | -0.026 | 0.005 |
| 2 | 20070112 | L95 | 2 | 9 | 1.208 | 1.017 | 0.015 | 0.009 | 0.012 | -0.007 | 0.003 |
| 3 | 20070209 | L95 | 2 | 9 | 0.640 | 1.006 | 0.026 | -0.021 | 0.012 | -0.040 | 0.010 |
| 4 | 20070215 | L95 | 2 | 9 | 0.640 | 1.054 | 0.020 | 0.004 | 0.010 | -0.037 | 0.005 |
| 5 | 20070215 | L104 | 1 | 7 | 0.775 | 1.091 | 0.079 | -0.008 | 0.054 | -0.052 | 0.012 |
| 6 | 20070220 | L98 | 1 | 7 | 1.121 | 1.033 | 0.011 | 0.012 | 0.003 | -0.018 | 0.007 |
| 7 | 20070311 | L98 | 1 | 8 | 1.121 | 1.017 | 0.008 | -0.024 | 0.001 | -0.035 | 0.006 |
| 8 | 20070314 | L98 | 1 | 8 | 1.121 | 1.031 | 0.011 | 0.018 | 0.002 | -0.014 | 0.008 |
| 9 | 20070424 | L104 | 1 | 5 | 0.811 | 0.918 | 0.232 | 0.052 | 0.213 | 0.093 | 0.049 |
| 10 | 20070424 | L101 | 1 | 5 | 0.584 | 0.903 | 0.257 | -0.124 | 0.165 | 0.005 | 0.155 |
| 11 | 20070424 | PG1323 | 1 | 4 | 0.847 | 0.998 | 0.059 | 0.023 | 0.017 | -0.004 | 0.040 |
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 adopted values and uncertainties
are the weighted average values and the weighted standard deviations:
(N the number of observations, deltaTi the uncertainty/error
on observation i)
Tbv = 1.032 +/- 0.023
Tb*Tbv = 0.002 +/- 0.027
Tv*Tbv = -0.025 +/- 0.015
Technical notes
Telescope and camera configuration.
Computer and software configuration.
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