[Aavso-photometry] 2MASS to Rc transform

[Michael Koppelman]

My thought (hope?) was that the three 2MASS colors might constrain the 
blackbody curve enough that one could make a reasonable extrapolation 
to Rc. For the stars I observe it is always hard to get reliable R 
magnitudes for comp stars and even V can be fairly dicey (in the 
V=11-16 range).

I will contact Doug and/or browse his web pages and see if he has a 
V/V-K to Rc transform.

Thanks!
Michael


On Sep 8, 2004, at 2:07 PM, Arne Henden wrote:

> The paper in question is Carpenter, J. K., "Color Transformations
> for the 2MASS Second Incremental Data Release," 2001, AJ 121, 2851.
> It is a good paper to read to see the variety of near-IR systems
> that call themselves "standard."  However, it is basically a paper
> that gives transformations from one JHK system to another JHK system.
> To go to Rc requires extrapolation, which never works, especially
> over such a wide wavelength range.
>   What people often do is to use a set of known standard stars and
> create a transformation from, say, V and (V-K), to Rc.  This works
> at an approximate level and is what I would do, since you can get
> "V" from Tycho, TASS or ASAS and "K" from 2MASS.  I think Doug West
> was trying a transformation like this, but I don't know of any
> published results from anyone.