[LEAPSECS] End of plausible equivalence between UTC and GMT

[Tony Finch]

Zefram <zefram at fysh.org> wrote:

> Gerard Ashton wrote:

> >The westernmost point of the London Borough of Greenwich

>

> Irrelevant.  The names "Greenwich Mean Time" and "Greenwich meridian"

> don't refer to the borough per se, but specifically to the transit

> instrument at the Royal Observatory, Greenwich.  (Historically there

> were two meridians so defined, from different transit instruments at

> the observatory.)


Greenwich Mean Time only referred to the timescale maintained by the
observatory, not to any particular transit instrument. As well as the
changes due to the move from the Bradley to the Airy meridian, there was a
change due to the move to Herstmonceux and the IERS virtual meridian, and
after 1972 the RGO seems to have treated it as a synonym for UTC.

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.

Tony.
-- 
f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/
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