Rob Seaman wrote:
[...] Many surveys and targeted
projects (at least in the optical/IR) produced data products - images,
spectra or catalogs - that are composited in some fashion from multiple
separate observations. Astronomers have traditionally found these to
be useful for many purposes, and some of these purposes have retained
some notion of an epoch and of time variability.
[...]

I'm not sure about some of the larger issues here, but I've had a
need to know the observation ending time, so for years I've had
a 'UTEND' keyword for that.


--
Bill Wyatt ) "remove this" for email
Smithsonian Astrophysical Observatory (Cambridge, MA, USA)