There is certainly merit in making a distinction among quantities such as
these. For example, one needs to be able to describe the interval of time
over which the data were obtained, as well as the effective duration of
the exposure. For example: an integration may be started, interrupted,
and then resumed. Or, multiple exposures of a region of sky may be
obtained separately and later combined. This is common in ground-based
IR, where sky brightness is an issue, or in the optical if the consecutive
exposures are obtained to track a time-variable phenomenon, or merely to
dither images spatially to remove artifacts such as seams in a large,
focal plane array. In these cases the interval over which photons were
collected is shorter than the difference between the start of the first
exposure and the end of the last. Somehow this information needs to be
recorded for high-level (i.e., combined) data products.
Depending upon the degree to which one wishes to obsess about the details, a richer semantic description may be in order.
Regards,
Dick Shaw
On Thu, 2 Mar 2006 12:52:39 +0000 (GMT)
Silvia Dalla <s.dalla-at-manchester.ac.uk> wrote:
>
> hi all,
>
> I propose modifying 'time.obs'.
>
> This UCD is currently defined as: 'Observation on-time, duration'
>
> However we are missing a UCD that identifies the time stamp associated
> with an observation: for example if data are collected between a
> 'time.obs.start' and a 'time.obs.end', frequently the mid point of
> this time interval is used to define the time of the observation.
>
> I propose that 'time.obs' should be 'time stamp associated to the
> observation'.
>
> A new UCD could be used to identify the duration of the observation:
> the obvious choice would be 'time.obs.duration'.
>
> Best wishes,
> Silvia
>
> ------------------------------------
> Silvia Dalla
> School of Physics and Astronomy
> University of Manchester
> PO Box 88
> Manchester M60 1QD
> UK
>
> Tel +44-161-306 8705
>Fax +44-161-306 3941
> ------------------------------------
#---
Dr. Richard A. Shaw, Scientist
National Optical Astronomy Observatory
950 N. Cherry Avenue
Tucson, AZ 85719
USA
520-318-8398
Received on 2006-03-03Z00:38:17