WHT time lost to technical problems
The plot below shows for each month
the fraction of night between dusk and dawn astronomical
twilights when the planned observations could not be carried out due
to technical problems. Engineering/commissioning nights,
service/discretionary nights and nights when observers were using their
own instrument, are excluded from the data.
The raw data (more up-to-date) from which the plot was constructed are
The fraction of
time lost to technical problems declined rapidly after 1992,
as newly-commissioned instruments and software systems
It has been around 1 - 3% since then, apart from 1998-9, when
a lot of time was lost to faults in an ageing data-acquisition
The downtime is due to faults occurring in many different
sub-systems, and is not easily reduced.
Technical downtime at other medium-sized optical telescopes is probably
as of the late 1990s,
3 - 4% was quoted for all of AAT, CTIO, KPNO, MMT and UKIRT.