[Aavso-photometry] survey photometry

[Michael Koppelman]

A hidden gem about these surveys (TASS, ASAS, NSVS, etc) is their 
measurements of *constant* stars. Once we know how to transform them 
all, we have many independent measurements by which we could probably 
determine fairly if not highly accurate photometry of a lot of stars. 
If you average 3 measurements each with errors in the neighborhood of 
0.1m you get an uncertainty of 0.06 or so. All the surveys probably 
beat 0.1 so we could maybe get in the 0.03 range?

Has anyone ever done this?

1. Create (or find) survey-to-Johnson/Cousins transforms for TASS, ASAS 
and NSVS. Determine the uncertainty in the transforms.
2. Average the measurements for a single star using many, many 
measurements from a given survey. Determine the uncertainty.
3. Determine the total error in the measurement based on the error in 
the average and the error transformations for a given star in a given 
survey.
4. Create a weighted average of all three survey measurements for a 
given star.

If you did that for all stars which all surveys have observed, you 
could then plot the uncertainty as a function of color and magnitude 
and get a pretty good idea of the useful range of the catalog. 
Something like that may be more useful than, say, Tycho.

Cheers,
Michael Koppelman
http://www.lolife.com/astronomy/