[daip] UVFIX (B1950 to J2000 coordinates)

[Eric Greisen]

Teddy Cheung wrote:
> Hi Eric,
> 
> Thanks for the quick response. I went ahead and compared the VLA cal
> manual B1950 and J2000 values vs. the pre and post-UVFIX values and
> found at most 3mas differences in each direction so am satisfied.
> 
> BTW, is there a handy formula/algorithm you use in UVFIX to do the
> B1950-J2000 conversion? I'd like to convert some B1950 values from the
> literature. I'm dissatisfied with the tools on the web -- e.g.,
> HEASARC does not give sufficient precision, and NED calculator does
> not seem to do this right (again, looking at the VLA calibrator
> positions; may be tied to a lack of precision).
>

We use a subroutine so no easy formula - the verb EPOSW does it but I do 
not know if you can enter and extract enough precision to be useful.

The subroutine EPOCHS inside $APGNOT/UVFIX.FOR is used for the B1950 to 
J2000 conversion.  You could probably borrow it and put a wrapper around 
it for your use.

Eric Greisen