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Jacobus Kapteyn Telescope


The Jacobus Kapteyn Telescope was taken out of service as a common-user facility as of August 2003

Coordinates of the JKT
Latitude: 28° 45' 40.1" N (+28.761°)
Longitude: 17° 52' 41.2" W (-17.878°)
Ground floor height: 2364 m

The Jacobus Kapteyn Telescope (JKT) has a parabolic primary mirror of diameter 1.0 m, and two interchangeable secondary mirrors. The telescope is usually fitted with the hyperboloid secondary mirror, which gives a conventional f/15 Cassegrain focus. The alternative f/8.06 Harmer-Wynne system uses a spherical secondary and a doublet corrector to give a field of 90 arcmin diameter for photographic astrometry over a wide field.

The JKT is equatorially mounted, on a cross-axis mount, which allows operation east or west of the pier. Normally it is east of the pier. The observing limits are currently:

  • Zenith distance < 84 deg
  • -6 h < hour angle < +18 h (telescope East of pier) 
  • -18 h < hour angle < +6 h (telescope West of pier) 
There are no explicit declination limits. The fully-lowered windshield which sits on the dome lintel sets a further limit. Because of the asymmetry of the telescope, the limits are different east and west of the pier.

A more detailed description of the optics and the mounting of the JKT is available in the Observers' Guide. For more information about the Telescope Control System please see the JKT TCS manual. For other documents see the manuals for JKT instruments.

For more information about the JKT, see the public information web pages.


The JKT was offered to visiting astronomers with the 2k × 2k SITe2 CCD camera and the JAG autoguiding box. The camera provides an unvignetted field of view of 10 × 10 arcmin, with a pixel sampling of 0.33 arcsec.


Most of the information required for operating the telescope can be found in the Observing Guide and in the Observers' Guide to JKT JAG-CCD imaging.

An ALPHA station lpas1 runs the telescope control system. Computer lpss10 hosts the observing system, i.e. data acqusition (UltraDAS), instrument control (ICS) and data inspection (IRAF).

NB at ZD >~ 45 degrees in the west, the tracking is poor. Jumps in tracking typically manifest themselves as double images on the CCD. Observers should therefore plan their observations to aovoid HA > 3 hours.

Quality Control

Reflectivity/scattering plots for the JKT mirrors:

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Contact:  (Head of Astronomy)
Last modified: 23 January 2013