 | The Carlsberg Meridian Telescope | |
TheCarlsberg Meridian Telescope (formerly theCarlsberg Automatic Meridian Circle) is dedicated to carrying outhigh-precision optical astrometry. It was until recentlyoperated jointly by the CopenhagenUniversity Observatory (CUO), theInstitute of Astronomy, Cambridge (IoA) and the Real Instituto yObservatorio de la Armada en San Fernando (ROA), however it is nowrun solely by the ROA.Although not one of theIsaac Newton Group of telescopes, it is nevertheless part of theObservatorio del Roque de los Muchachos onLaPalma. It began operation in May 1984. When the telescope was first moved to La Palma in 1984 it was one of thefirst fully automatic telescopes in the world. When the skies were clear aselection of stars (about 500 a night) would be made and at about sunset thedome would open automatically and start observing. An observer would bepresent on the site (usually in the flat underneath the telescope), butwould only be needed if there was a failure of a piece of equipment. Clickhere for more information on the oldsystem. In the spring of 1997 a further stage of automation was made when weconverted the telescope to remote operation. Since then, the telescope has beenoperated over the Internet from Britain, Denmark or Spain and no observer hasbeen present at the telescope. Most of the problems can be solved over thenetwork, but sometimes local help is needed. By operating in this way aconsiderable saving is made on travel costs. The main task that is currently being done by the telescope is to map theNorthern sky using the upgraded CCD detector. This will give accurate positions ofstars, allowing a reliable link to be made between the bright stars measuredby Hipparcos and the fainter stars seen on photographic plates (as measuredby the APM and similar measuring machines). The current area of the survey is between-30° and +50° in declination and has been recently completed. At the IAU General Assembly in Manchester (August 2000) a meeting was heldon astrometric surveys. The viewgraphs from themeeting arehere. The results of observations with the old micrometer were published annuallyin catalogues. As well as the positions and magnitudes,the catalogues contain the improved proper motions of many stars derived bycombining the Carlsberg position with previous epoch observations retrievedfrom a data-bank. The average accuracy of the proper motions so derived is0.003 arcsec/year. Catalogues 10 and 11 were finished in June 1999 and were the last to be published using data from the oldmicrometer. Carlsberg Meridian Catalogues numbers 1 to 11 can now beinterrogated online via the interface at theUK Astronomy Data Centre.Alternatively, the complete data files from the CD-ROM for CMC1-11 can be foundhere. Carlsberg Meridian Catalogue 14 has been released (31 December 2005). This is anastrometric and photometric catalogue of 95.9 million stars in the red(SDSS r') magnitude range 9 to 17.This catalogue covers the declinationrange -30° to +50° and supercedesCMC12which covered -3° to +3° andCMC13which covered -3° to +30°. From observations of about 50 photometric standards, the Carlsberg MeridianTelescope provided nightly values ofatmospheric extinction in V for La Palma. The data is split up intoyearly files going back as far as 1984. The most recentfile is that for 2010.From the end of 1999 March this differs from the previous years as it isderived from the newCCD camera which works in theSloan r' band. For more information lookhere. Measurements of temperature, pressure, windspeed, wind direction and humidityat the site are taken every 5 minutes day and night. This large database ofmeteorological recordsis available to interested persons directly over the web. Details of past projects of the CMT using the old micrometer can be foundhere. A bibliographyfeaturing Carlsberg observations is available. Some more views of the Carlsberg Meridian Telescope. The project is under the supervision of ROA. The main contact is: Señor J.L.Muiños Tel : +34 956 599000 ext 35605Description
The telescope is arefractor with an objective of 17.8 cm diameter and focal length of 266 cm.The observing procedure is entirely automatic, with the acquisitioncontrolled by a Pentium PC. The data reduction is carried out in themorning on another Pentium running Linux.
In June 1998 we changed the detector froma photoelectric scanning-slit micrometer to a Charge Coupled Device (CCD)mainly operating in drift-scan mode. This has not only helped us observefainter stars, but it also has enabled us to observe many stars at once.This one improvement has increased the number of stars we observe a night bya factor of more than 20.
The most recent development (April 1999) has been to upgrade theCCD systemto a 2k by 2k chip and to fit a SDSS r' filter. These and other improvementswith the CCD have allowed us to observe about 4 times as many stars withthe new CCD. Our current magnitude limit is r'=17 and we observe between100,000 and 200,000 stars a night.There is also an RGO leaflet onMeridian Astronomy.Current Aims
Results
Astrometric links
Pictures of the telescope etc.
Contacting us
Real Instituto y Observatorio de la Armada en San Fernando,
Seccion de Astronomia,
11110 San Fernando,
CADIZ,
Spain
FAX: +34 956 599366
E-mail: ppmu@roa.es
Dafydd Wyn Evans / IoA / dwe @ ast.cam.ac.uk
Last update 5 January 2010
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