[Aavso-photometry] ASAS182612 Campaign & CIs of Comparisons

[Greg Crawford]

I am attempting to arrive at standardised measurements of ASAS182612, as per the
campaign advised in Alert Notice 351.

 

Using the general formula:

M = m-X(k'+ k"CI) + (Tm*CI) + ZP

where Tm = transform for the single colour (not colour index), and

           CI = standard colour index of the object.

 

and the reduction technique in my software, it is necessary to know the CIs of
the comparisons in order to work out the CIs of the target. So with transform
coefficients, first order extinction and nightly zero points now worked out, it
seems I need CIs for the comparisons, which will lead to CIs for the target, and
thus the ability to convert m to M. 

 

Alert Notice 351 gave colour indices for one comparison star, namely the comp at
18:26:09.44 +12:17:37.2 (no. 119 in the AAVSO star chart). My questions are,
should I use just this one comparison star, or use all four provided in the
chart (numbered 109, 119, 133, 134)?  If the latter; where do I get the colour
indices for the other three comparison stars from?

 

Greg Crawford

 <http://www.nelsonbay.com/~gc/observatory.htm> Bagnall Beach Observatory