How does the Schmidt telescope work?
This reflecting telescope is a camera, imaging directly onto
glass photographic plates. Before its invention, astronomers were
unable to photograph large areas of the sky in any great detail.
Instead, they had to build up a picture using narrow images, which
was extremely time consuming and meant larger objects were
sometimes missed, or use smaller lenses, which could not capture
faint objects.
This camera telescope was invented in 1930 by Bernhard Schmidt
(1879-1935), a Swedish-Estonian optician. Schmidt’s groundbreaking
solution was to use a spherical mirror within the telescope,
correcting distortion (known as ‘spherical aberration’) with a
thin, aspheric lens, now called a ‘Schmidt corrector plate’.
Because its revolutionary design provided a large field of view, it
could photograph bigger swathes of sky, far more quickly. The
images it produced could be used to build up an atlas of the
sky.
Click on the thumbnails below to see examples of the images
capture by this Schmidt telescope. Images © Royal Observatory,
Edinburgh.
Where does our telescope come from?
This particular telescope was one of the first Schmidt
telescopes to be set up in a British observatory. It was installed
in 1951 in the West Dome of the Royal Observatory on Blackford
Hill, Edinburgh. The mount is prominently dated 1930; this is
because it was reused from a previous telescope.
In the early 1960s this telescope became the most widely used
telescope on Blackford Hill. From 1970, images taken with it were
used in the observatory's pioneering development of a plate scanner
to convert glass astronomical photographs to digital data. This
telescope retired later in the 1970s and the four inch glass
photographic plates it used are no longer made.
From 1973 the astronomers of the Royal Observatory, Edinburgh
operated the UK Schmidt telescope in Australia, at a site further
away from air and light pollution, and with better weather.
You can find out what it was like to use
the Schmidt telescope here.
How was the telescope installed in the museum?
Removing the telescope from the dome at the Observatory was
something of a challenge, made possible through the fortuitous
timing of major restoration work to the dome and the experience of
our engineering conservation team and contractors. Before it was
removed from the Observatory, it wasn’t even possible to tell how
much the telescope weighed, as it was perched on top of a column,
or pier, about 10 metres tall. We now know it weighs over 3.2
tonnes!
The telescope was unbolted into two main pieces and hoisted from
the Observatory by crane (on a beautifully clear, but absolutely
freezing March morning) and removed to the aircraft studio at the
National Museum of Flight for conservation, as our conservation
unit at the National Museums Collection Centre was too crowded with
other objects for the new galleries.
It now takes pride of place in the Earth
in Space gallery, which investigates our planet’s place in the
universe.
Above: The new Earth in Space gallery.
With thanks to the UK Astronomy Technology Centre, who donated
the telescope to the Museum.