No subject

[Tim Naylor]

> Okay, I'd like to bring up my current pet peeve about the NVO cone search
> standard (ie http://www.us-vo.org/metadata/conesearch/), which is that it
> doesn't include either equinox or epoch.

Let me add my take (as an astrophysicist) on this.

1) Epoch.  If you change the epoch of a cone search the answer should 
change, that's because some high proper motion objects will move through 
the cone with time.  So, a database with proper motions should accept and 
use an epoch.  A database without proper motions should return what epoch 
the data refer to.  Without this, cetrain science programmes will be 
impossible (e.g. proper motion studies).

2) Equinox really should be dealt with, and dealt with properly.  Its all 
very well to say "everything in the VO will be equinox 2000", but it seems 
to me to be building in a serious limitation at an early stage.  Folks 
should be making the data available in what ever equinox is needed, and 
then it should be converted (on the fly?) to what the user wants.  If not, 
how are we going to cope if there is another change such as that from 
Besselian to Julian equinoxes?

				Tim


-- 
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Prof. Tim Naylor,
School of Physics,
University of Exeter,
Stocker Road,
Exeter
EX4 4QL

E-mail: T.Naylor at exeter.ac.uk
tel: 01392 264172
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