roy at cacr.caltech.edu
Mon Jul 2 12:23:18 PDT 2007
> STC already has several representations for reference date-time and offset date-time, and Arnold is also taking the lead for the FITS WCS paper on time. STC has a list of time scales which may have any sort of precision meaning. So, please, let's wait on this until Arnold returns.
There is a fundamental question here, and I have not heard an answer
from the group. The question is should our standard allow a rich variety
of time standards?
There are may time standards: atomic clock, Earth rotation, barycentric,
topocentric, ISO8601, Julian Days, differential time from a fixed point,
what time is it at Pluto, etc etc. If the light-curve standard allows
ANY time standard (such as the long list of STC standards), then
providers are happy, especially those who have observatories on Pluto,
because they don't need to change anything except formatting. However,
consumers would NOT be happy to be forced into all this extra data
reduction. However, if the standard is very RESTRICTIVE about time
standards, then consumers are much happier. I am at an LSST meeting
right now, and have independently asked three astronomers about time
standards for light curves: one said MJD only, one said HJD only
(heliocentric), and the other said use either MJD or HJD.
--> Can we agree to adopt one/two varieties of JD as the time standard?
Make our lives simpler, get acceptance in the astronomy community from
--> To turn that question around -- who will suffer if all the world's
exchange of light-curve data is based on MJD/HJD?
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