Datatype: da0 CCD
The Delta a photometric system has be designed by Maitzen to detect photometrically
peculiar stars (Ap). The original system is based on photoelectric photometry.
The da CCD system is the realisation of the original da system
with a CCD detector.
It uses three filters g1, g2 and y and the parameter a is defined as
a = g2 - [(g1 + y) / 2].
Δa is computed relatively to a linear relation : a versus (B-V) or (b-y) or (g1-y).
For young open clusters with differential reddening, dereddened magnitudes and indices have
been used, and a new datatype, da0ccd, has been introduced.
|V0||:||Unreddened V magnitude|
|a0||:||Dereddened a parameter|
|g1-y0||:||Dereddened g1-y colour index|
|Da0||:||Deviation from the normal relation|
|ebv||:||E(B-V) colour excess|
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Last Update: 22 January 2006