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INGRID timing error

A discrepancy between the integration time (as reported in the FITS headers of the images) and the real integration time, is present in all INGRID images obtained since the commissioning of the instrument (March 2000). Since then, different versions of the timing board software were running in the detector controller (SDSU), with a different "timing error" associated to them.

Below are summarized the corrections which should be applied to the reported integration time (in the FITS headers of the images) in order to get the real on-sky integration time for each of the sofware versions of the SDSU controller.

Further inforrmation about the INGRID integration timing error associated to version 3.2 can be found here.

NOTE: There is not timing error with UltraDas (i.e. since 1st September 2001).

Version 3.2 (from 1st March 2001 to 31st August 2001)

In order to get the real on-sky integration time of the INGRID images obtained with software version 3.2 of the timing board of the SDSU controller, the following should be done:

Version 3.1 (from 5th May 2000 to 28th February 2001)

Other cases (observations obtained before 4th May 2000)

The exposure time as recorded in the FITS headers must be increased by 0.146 seconds only, independently of the number of non-destructive readouts (keyword INGNR) performed.

NOTE: The corrections above (for all the 3 cases) do not depend on the number of coaverages performed (keyword INGNC in the FITS headers).

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Last Updated: 23 September 2001
Almudena Zurita azurita@ing.iac.es