Historical Values Patrick A. Wayman's book "Dunsink Observatory
1785-1985" gives some historical latitude and longitude
measurements for Dunsink. The figures quoted for longitude are:
• Rev. Dr. Henry Ussher (who worked at the observatory from
about 1783 to 1790) had made various observations which give values
about 25m48s, 25m18s and 25m07.4s The last is dated 1787. •
Rev. Dr. John Brinkley (who worked from 1790-1826 and may have been
Bishop of Cloyne) made a measurement reported by Hamilton in 1832
of 0h25m22s. • T. Romney Robinson of Armagh worked with
Hamilton to make a detailed determinations for Dunsink and Armagh.
His result was 0h25m21.08s, with an error of about 0.1s. This was
about 1838. • The Nautical Almanac continued to use Brinkley's
value until 1896, when it moved to Robinson's value of 25m21.1s.
And the figures quoted for latitude: • Brinkley gave values of
53o23'13''.5 or 53o23'14''.2, depending on the refraction tables he
used. In a later paper he gives a value of 53o23'12''.6. Hamilton
recommended a value of 53o23'13'' for the Nautical Almanac, which
was used from 1835 to 1895. • In about 1874 Brünnow did
further measurements, that gave a similar answer to Brinkley,
53o23'13''.0. • Rambaut verified these results in 1889,
53o23'13''.08 with an error bound of about 0''.04. This made it
into the Nautical Almanac in 1896. The 1935 Nautical Almanac (p.
684) uses these figures, which show that the altitude is pretty
good too. No Place Long Lat Alt 80 Dublin, Irish Free State
+0h25'21.1'' 53o23'13.1'' 86m Dunsink Observatory, Trinity College
One of the other important observatories in Ireland is Armagh
Observatory. A trip there with a handheld GPS gives a location of
around 54o21'10.2''N, 6o38'52.6''W, 60m. This seems to be in
reasonable agreement with standard figures of around 54o21'12'' and
6o38'54. Its most famous director was William Rowan Hamilton, who,
amongst other things, discovered quaternions, the first
non-commutative algebra, while strolling from the observatory into
the centre of the city with some friends and his wife. He is also
renowned for his Hamiltonian formulation of dynamics. In the late
20th century, the city encroached ever more on the observatory,
which compromised the seeing. The telescope, then no longer state
of the art, was used mainly for public 'open nights'.
The location of the cache is near Elm Green Golf Centre which is
adjacant to the Observatory on Dunsink Lane. You do not have to
enter the centre to discover the cache, however I recommend a visit
if you have time. No fee to look and enquire about its facilities.
It boasts that it has 110 acres of lush green fairways and stunning
views just 10 minutes from the centre of Dublin. I know this to be
true as I have played here with fellow geocaching friends. The
container is a small brown plastic container with a screw top. Bit
like a stubby bottle.