Hamburg Observatory - Overview:
Buildings & Telescopes
The Oskar-Lühning Telescope is the largest instrument at Hamburg Observatory,
and currently the second largest telescope in Germany. It is a Ritchey-Chretien
system with 1.20m aperture and a focal length of 15.60m in the Cassegrain focus.
Built in 1975, it is also the youngest telescope at the observatory.
Building and mounting, however, date back to 1954. They housed originally the
Big Hamburg Schmidt Telescope. The building also houses a
metallizing facility, for large mirrors
which is still in operation today.
Its existence owes the telescope to the foundation of Bergedorf's headmaster
Nikolaus Lühning. His son Oskar intended to study meteorology and
astronomy, but at the beginning of World War II he had do join the Wehrmacht
(army), and was lost in Russia since 1943. With no other heirs, the
Lühnings left their fortune to the university to be spent - according to
their son's intentions - on the advancement of astronomy.
In the mid-seventies, the plan was realised to relocate the Big Hamburg
Schmidt Telescope to the
Calar Alto Observatory (Spain). The telescope could no longer be effectively
used: its large focal ratio made it too sensitive of the bright night sky of
Hamburg. Because of the different geographical latitude of South Spain, a new
mounting was required. The telescope was taken down in June 1975, while the
fork mounting remained in its dome in Hamburg.
For some time, Hamburg Observatory had intended to obtain a modern 1.3m telescope
for spectroscopic and photometric investigations of single objects. The
university, though, had been unable to provide the neccessary means. Now in 1974,
thanks to the Lühning-Foundation and additional means from the Hamburg
Senate, the new telescope could be ordered from Grubb-Parsons (Great Britain).
Near the end of 1975, the instrument was set up in the former Schmidt dome in the
old fork mounting. It was named Oskar-Lühning-Telescope in honour of the son
of the founder. Due to its smaller focal ratio it is less strongly
affected by light pollution than the Schmidt telescope.
After some adjustment problems were solved, the telescope was used until the
mid-eighties, primarily for photoelectric measurements. Further works included
(among other studies) determinations of angular diameters of planetary nebulae, and
spectroscopic observations of novae and Beta - Cephei stars. The latter
purpose made use of a grid spectrograph, bought in 1973 with money from the VW
foundation, which unfortunately proved to be technically insufficient.
Since 1994, after several years without scientific observations, the
Oskar-Lühning Telescope is occasionally used to obtain CCD images
Hale-Bopp). The electrical and/or mechanical parts of the mounting, by that
time more than 40 years old, caused occasional problems, and the dome seeing is
often less than optimal, because of the heated yet badly isolated office rooms
in the storeys below. In 1998 the telescope was closed for reconstruction. At
first only mechanical improvements were planned, but later one realized, that
the telescope - if equipped with a powerful CCD or
a modern star spectrograph with high resolution - could be successfully used
for a variety of observational purposes.
The works were completed in 2001, and a modern CCD camera from Apoge with
1024x1024 pixels and a visual field of 5'x5' was installed. The telescope was
converted into a robotic telescope, i.e. it can now be fully run via internet
from anywhere in the world. With the contruction works Hamburg observatory
gained a lot of knowledge which can be used for, e.g. the STELLA
project. As a modern telescope it can be used for practice how to work with
modern telescopes and it can be presented to the public for explaining how
observations are performed. The scientific output will not be very large, since
weather and light conditions in Hamburg are poor, but because of the good
access the telescope can be used, e.g. for tracing long term variablilty.
German text and images by
Hünsch; English translation by Kerstin Molthagen