Specifications

AUTOSTAR CCD PHOTOMETRY 29
5. Advanced Data Reduction
5.1 Reducing the Raw Magnitudes to Standard
Magnitudes
So far all or our work has produced raw (instrumental) magnitudes
that are unique to the equipment used to produce them. Raw
magnitudes are fine, if you are only interested in changes. Many
times, data may be desired to be combined with data taken with
other equipment. Calibrating the data to a standard will allow it to
be useful. Once calibrated, your data will represent true
magnitudes. To do this, the raw magnitudes must be corrected with
color transformation coefficients. See Appendixes C and D for the
details on determining these coefficients.
5.2 Transformation Coefficient Equations
(R – I) = γ *(r – i) – k'
ri
* X + ζ
ri
(V – I) = α *(v – i) – k'
vi
* X + ζ
vi
(V –R) = β *(v – r) – k'
vr
* X+ ζ
vr
V = v +ε * (B – V) – k'
v
* X + ζ
v
(B – V) = μ * (b – v) – k'
bv
* X + ζ
bv
Where:
Instrumental Magnitudes
Instrumental Magnitude = –2.5 * log
10
(Star Counts)
iv
rb
Corrected Magnitudes
I V (V – I) (V – R)
R B (R – I) (B – V)
Transformation Coefficients (Must be determined)
α for (V – I) ε for V
β for (V – R) μ for (B – V)
γ for (R – I)