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CMAIMAGE - EXOSAT CMA Images for Each Pointing



This database table contains the images from two EXOSAT LE telescopes with the channel multiplier array (CMA) detectors in the focal plane. The CMA/telescope combination covers the 0.05-2.5 keV energy range with a field of view of 2 degrees and an on-axis angular resolution of 24 arc seconds (HEW). The detectors had no intrinsic spectral capabilities; however, different filters were used to make broad band measurements. The most commonly used were Thin Lexan (number 7), Aluminum-Parylene (number 6) and Boron (number 8). An image was generated for each filter used during an observation.


De Korte P.A.J. et al., 1981, Sp. Sci. Rev., Vol. 30, p. 495.

White N.E. and Peacock A.P. 1988, in X-ray Astronomy with
  EXOSAT, [eds. N.E. White and R. Pallivicini], Memoria S. A. It, p. 59.


This Browse table was created in March 1995 and updated in October 2003.

Data Products

An image is available for each filter used during each observation. The images are in linearized detector coordinates and de-blurred (to account for fluctuations of the pointing position which were quite small). These images created originally at the EXOSAT Observatory were in a compressed binary format. The HEASARC converted these images to FITS format. The images are also provided in GIF format. Each GIF file includes two different views of the EXOSAT field. The left view shows the complete FOV (2 X 2 degrees), while the right view shows only one degree around the central region.


This parameter contains the original target/field name chosen by the principal investigator (PI) and used in the EXOSAT observation log.

The Right Ascension of the pointing position.

The Declination of the pointing position.

The Galactic Longitude of the pointing position.

The Galactic Latitude of the pointing position.

The name of the associated image file.

The observation start time. Accurate to the nearest second.

The date the data was processed.

The instrument paramater records which of the two telescope+detector combination, LE1+CMA1 or LE2+CMA2, were used in the observation to detect the source. The values are L1, for the combination LE1+CMA1, and L2, for the combination LE2+CMA2.

Some observations were carried out with an OBC program that sets a 'diamond' filter. This filter electronically screened out the outer part of the field of view. The resulting image, which is shaped as a diamond, covers only a fraction of the 2 degree X 2 degree field of view. If the diamond filter was in use, then this parameter is set to 1; otherwise, its value is 0.

The filterwheel position corresponding to the following filters:

    2 = PPL
    3 = 4000 (thick) lexan
    6 = Al/P
    7 = 3000 (thin) lexan
    8 = boron

The distance from the center of the detector to the pointing position in arcminutes. This parameter is usually 1-4 arcminutes because of a deliberate random offset put in to the pointing to avoid always the same spot on the detector being exposed by the source.

The total on-source observation time in seconds. This includes all dead time effects, interruptions in coverage, etc.

The sequence number of the observation.

The number of the archived tape where the files are stored.

A number unique to each Principal Investigator.

The type of proposal (HLX, etc.)

The 21-cm NH through the galaxy in cm^-2.

The name of the file containing the associated background lightcurve. One background lightcurve is associated with each image.

Contact Person

Questions regarding the CMAIMAGE database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 8-Nov-2004