On Jan 13, 2009, at 11:57 AM, Brad Cavanagh wrote:
>
>
> Observation 54 from 20081007 ends up in its own group because it has
> a difference reference RA/Dec. You can see this by doing 'ndftrace
> a20081007_00050_01_0001 fullframe' and 'ndftrace
> a20081007_00054_01_0001 fullframe'. For observation 50 the reference
> Declination is -1:54:27, whereas for observation 54 it's -1:54:10.
> This change in the reference position means they get split up into
> separate groups -- the reference position has to be the same to
> within an arcsecond. I can adjust this "slop" though, if necessary.
>
Little bit of clarification here. The AST nomenclature is Sky
Reference but that is not to be confused with a heterodyne REFERENCE
position (the off position). Here Brad is saying that the BASE
position has changed between observations. Since oracdr does not want
to start doing astrometry itself it looks at the base positions and
uses those to decide when to group (the JSA will be cleverer). It
assumes that you will use offset iterators in the OT to move around
your field rather than changing the telescope base position.
--
Tim Jenness
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