Summary: Meteorological Data recorded at Armagh Observatory from
1795 to 2004: Volume 10 � Daily, Monthly, Seasonal and
Annual Hours of Bright Sunshine 1880�2004
C.J. Butler, M. Emerson, A.M. Garc��a�Su�arez, E. Pall�e and S.T. Kelly
Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
Introduction
A daily record of sunshine hours at Armagh Observatory, using a standard Campbell�Stokes
sunshine recorder, commenced on 21 April 1880. From that date until October 1885 there are
several gaps in the data but, subsequently, the records are regular and consistent. Here we tabulate
the daily, monthly and annual total sunshine hours recorded at Armagh up until the end of 2004.
The Campbell�Stokes Sunshine Recorder
The original design of the bright sunshine recorder used a water filled glass sphere to focus
the rays of the Sun onto a paper strip where a burnt trace was produced. A later version, which
subsequently became standard, employs a solid glass sphere (see Met. O#ce Observers Handbook,
1982). The sustained use of the Campbell�Stokes recorder for over a century probably owes more to
the desirability of continuity than its ability to record a scientifically well defined parameter. Even
when well adjusted and maintained, it tends to over�record periods of intermittent bright sunshine
and to under�record periods of hazy sunshine or weak sunshine when the Sun is at low altitude. In
addition, the measurement of bright sunshine using the Campbell�Stokes recorder is susceptible to
error from a number of other sources such as : (i) a non�uniform horizon due to the proximity of

Source: Armagh Observatory

Collections: Physics