OHP 80cm CCD camera

Haute-Provence 80-cm telescope CCD camera

News:

We are making available an Andor DW-436-BV system, the spare camera of the TAROT projet (PI Michel Boer). This camera has a 2048x2048 pixel Marconi back-illuminated CCD cooled by a 5-stage Peltier system to -50 C. See ANDOR for more details. The field of view is 7x7 arc-min (pixels of 13.5 microns). The Cassegrain adapter is the same with the same filter set. The acquisition software is AudeLa. See also obs-psr for more information.

Introduction

The OHP 80cm telescope, financed by the Dina Foundation and designed by A. Couder, was built in Paris ca.1930 and was set up at Forcalquier in 1932 prior to the founding of OHP. It became the second to be installed in Saint Michel (after the 1.20m), where it was re-commissioned in 1945. It is used now exclusively in its f/15 Cassegrain configuration, although a f/6 Newtonian focus could still be accessed if necessary. The focal distance is 12 meters, yielding a focal plane scale of 58 µ per arc-second. The refurbishing of the 80-cm telescope started a couple of years ago but much remains yet to be done.

An adapter (on extended loan from the Bureau des Longitudes and built by the Observatoire de Bordeaux) was fitted to the telescope in early 1996. This adapter houses a 6-position filter wheel, an iris shutter and an auto-guider. The dewar containing the CCD and the preamplifier are attached to the adapter. The camera controller is bolted to the Cassegrain base-plate. The signal from the controller is transported to the observing room by an optical fiber cable. The ensemble adapter+dewar+controller is called the CCD camera. All basic functions of the camera are computer-controlled from the observing room, with the exception (for now) of the filter wheel --whose position must be selected manually at the telescope. Pointing and slewing, as well as turning the dome are done manually.

Filters

The filter wheel accepts 6 filters of 50-mm diameter. They are twins of those used at the 1.20m. Several broad-band filters exist (U, Cousins BVR and Gunn uvgriz. The Gunn i is used as a 'Cousins I' since the transmission curves are quite similar). Interference filters centered on interesting emission lines are also available. Each filter is fitted with an optical compensator so that no change in focus is needed when using different filters.
Filter transmission curves
List of all available filters

Pointing and Tracking

The telescope's drive electronics were developed in-house. Actual tracking of the telescope is done by a stepper motor which drives a tangent screw/sector-wheel system for as long as 3 hours. The sector-wheel must be reset after this time interval. The telescope coordinates are now still set by using the original setting circles.

S.A.Ilovaisky
26 June 1997; updated 28.05.06