Decommisioned instruments

Since 1973 four instruments have been mounted at the cassegrain focus of the 182 cm telescope.

Currently only two instruments are available. The characteristics of two decommissioned instruments are given below.


At the Cassegrain focus an adapter is used with the CCD camera and the filters wheel for direct imaging.

The CCD camera consists of three main parts:

  • the cryostat with the CCD sensor

  • the analog-electronics

  • the control-system.

The control system is located in the Coude' room and is connected to the remaining parts through a 30 m link.

The whole system is controlled by the operator either from the Coude' room or from the dome room. Off-set guiding through an intensified TV-camera is possible both at the console in the dome and in the Coude' room. About 30 broad and narrow band filters are available at Ekar which are listed in table. When specifying a filter to be installed in the instrument, please use the Ekar number. The transmission curves of the filters are not given; these curves can be found in the Ekar Filter Inventory (in preparation), a copy of which exists in the Ekar library. The filters are classified according to their band width (broad or narrow) and to their central wavelength. The last column gives the starting wavelength of the red leak.

Table 1. Johnson and Cousin Filter

Table 2. Gunn Filters

Table 3. Interference Filters


The Boller and Chivens spectrograph has been equipped with the "Dioptric Blue Galileo Camera" with a focal length of 188 mm and an off - axis parabola collimator with 90 mm of diameter and a focal length of 810 mm.

There is a comparison source, a hollow cathode Fe - Ar lamp, for wavelength calibration.

There are five gratings available for the B&C spectrograph with dispersion ranging from 42 A /mm to 339 A/mm. Gratings can be changed, but the spectrograph must be refocussed after every change. Refocussing can take up to 2 hours and it is therefore not recommended during the nights observing.

In the table the available gratings are shown together with their principal characteristics: