[LEAPSECS] telescopes and observatories

[Rob Seaman]

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