[LEAPSECS] telescopes and observatories

[Tony Finch]

Rob Seaman <seaman at noao.edu> wrote:

> Tony Finch wrote:

>

> > 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".


See section 5.5.6.1 "Introduction of the new definition of UTC" of
http://www.lib.cam.ac.uk/deptserv/manuscripts/RGO_history/rgo_home_ch5.html

  "Secondly, the signal continued to be known as the Greenwich time signal
  and it was normally referred to as GMT. Thus once again, the meaning of
  GMT was ambiguous, as this abbreviation was used for both Greenwich mean
  solar time, which closely followed the variations in the rotation of the
  Earth and was the argument in the tables in the navigational almanacs,
  and for coordinated universal time, which was based on International
  Atomic Time (TAI). A change in the meaning of GMT had previously
  occurred in 1925 when the start of the day in the Nautical Almanac was
  changed from noon to midnight to conform with civil practice and with
  the recommendations of the prime meridian conference in 1884. The
  Nautical Almanac continued to use GMT with its original meaning, but it
  eventually changed to the heading "UT (GMT)". [Dr Donald Sadler,
  Superintendent of the Nautical Almanac] mourned the change in the
  meaning of GMT and used to wear a black tie to mark the occasions,
  usually on New Year's Eve, when a leap second was introduced."


> > 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.


Well spotted :-)

Tony.
-- 
f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/
Sole: Variable 3 or 4, becoming southeasterly 4 or 5 later in west. Moderate,
occasionally rough at first. Showers. Moderate or good.