Tony Finch wrote:
> Greenwich Mean Time only referred to the timescale maintained by the
> observatory, not to any particular transit instrument.
For a more nuanced perspective:
http://www.worldcat.org/title/quest-for-longitude-the-proceedings-of-the-longitude-symposium-harvard-university-cambridge-massachusetts-november-4-6-1993/oclc/034878901
> after 1972 the RGO seems to have treated it as a synonym for UTC.
See rather: http://ucolick.org/~sla/leapsecs/timescales.html
The only coherent astronomical usage of the term would be "mean solar time on
the prime meridian". This has indeed always been a practical synonym for UTC.
It will not remain so if the "Draft Revision to ITU-R Recommendation TF.460-6"
is passed. This is a problem with the draft. Reinterpreting history won't get
rid of it.
> Continuing Gerard's theme, I think the westernmost outpost of the Greenwich
> Observatory was the Roque de los Muchachos Observatory on La Palma in the
> Canary Islands, where the 2.5m Isaac Newton Telescope was moved from its
> original installation at Herstmonceux. La Palma is at 17°52′W.
This is beside the point.
Many observatories maintain multiple sites distributed in longitude or between
the northern and southern hemispheres. The former provides coverage in time,
that is, angle on the sky. The latter to reach areas of the sky otherwise not
visible from a particular location. Several ongoing projects have built (or
plan to) telescope networks that girdle the world.
An observatory is a scientific organization. A telescope is a physical
instrument at a particular site. Even multiple-telescope projects correspond
to some coherent-if-complex ObservatoryLocation coordinate system expression.
Greenwich Mean Time has always had a meaning in relation to the prime meridian.
If the goal here is to make it seem like some free parameter and therefore
that the "Universal Time" part of UTC is a free parameter, this A) won't
succeed, and B) is a dangerous strategy to follow if any of our standards are
going to remain coherently tied to the real world.
The message of Steve Allen's remarkably thorough list of timescales is rather
that more coherence needs to be brought to these efforts.
Rob
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