| Sherwood Observatory - Inside the
dome |
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Sherwood Observatory
The idea to form a local astronomical society in the Mansfield / Sutton-In-Ashfield
area came about in late 1969, when David Collins placed an advert
in the local newspaper with the intention of contacting other people
with a similar interest in the area.
History
After considering various locations for the proposed Sherwood Observatory,
one location stood out as the most suitable, and thanks to the help
of three key parties we were able to secure the present site on Coxmoor
Road, on one of the highest points in Nottinghamshire.
Initial site preparations commenced in 1972, and the observatory foundations
were gradually dug out.
The dome itself is 22 feet in diameter, and was designed with the
help of the Nottingham University Architects department.
The observatory was officially opened in 1986.
The main Sherwood Observatory telescope uses a system of mirrors,
in a Newtonian configuration.
The telescope
A 61-cm diameter main (primary) mirror collects light from the object
being observed. Light is reflected up the tube to a flat mirror inclined
at 45°.
The secondary 'flat' mirror is supported by a 'spider' system. This
is the cause of 'crosses' that can sometimes be seen superimposed
on photographs of stars.
The image is then deflected into an eyepiece focussing assembly affixed
to the side of the telescope tube upper section.
Individual eyepieces provide a range of magnifications. Lower and
intermediate powers are most frequently used.
Seeing conditions determine how much magnification can be applied.
High magnifications are effective only when the atmosphere is stable.
A single lens reflex camera body can be used in place of an eyepiece
to photograph the Moon, planets, stars and a wide range of other objects.
The CCD camera captures images more rapidly and these can be analysed
on a PC.
Video cameras provide a convenient medium for displaying objects to
large numbers of people.
This method also shows how atmospheric turbulence - known as 'seeing',
determines image quality.
The telescope is driven to counteract the Earth's rotation, enabling
objects to be kept in the field of view.
Bright objects such as the Moon, planets and stars down to naked eye
visibility can be found by using the Telrad to 'point' the telescope.
This device does not magnify, but displays in a headup mode, an illuminated
reticle For fainter objects, where pointing accuracy becomes more
critical, the 61-cm reflecting telescope onboard NGC-miniMAX computer
system is applied.
This holds a database of several thousand items, including nebulae,
galaxies et al The CCD camera used at Sherwood Observatory is a Starlight
Xpress SXL8 large format CCD camera. |
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