sla at ucolick.org
Mon Jul 2 13:06:43 PDT 2007
On Mon 2007-07-02T12:23:18 -0700, Roy Williams hath writ:
> 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?
Who are you serving?
> 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.
One size may not fit all.
> 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.
On the surface this lack of precision in response implies no
familiarity with the work of IAU RCMAM over the past two decades, nor
with everything explained nicely by Lindegren and Dravins
This is undoubtedly why one of the goals in the charter of the new IAU
Comm 52 is "deepen understandings of the above results among
astronomers and students in astronomy".
> --> 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
> the start?
If you are serving asteroid rotation and Cepheid/RR Lyrae light
curves, and even probably many instances of microlensing, then it
really doesn't matter. The observations were probably not even
timestamped well enough to distinguish.
> --> To turn that question around -- who will suffer if all the world's
> exchange of light-curve data is based on MJD/HJD?
If you are serving x-ray pulsations, or if observations
of millisecond pulsars count as light curves then the model
had better be as good as the TEMPO code described in
Just saying MJD/HJD is definitely not going to do the job.
Steve Allen <sla at ucolick.org> WGS-84 (GPS)
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