Re: The unid with slooh

From: Marco Langbroek (
Date: Tue Nov 26 2013 - 15:49:35 UTC

  • Next message: Kevin Fetter: "Re: The unid with slooh"

    Are the originals in FITS format?
    Normally, time tags should be in the FITS header, along with an indication 
    whether it refers to start, middle or end, and what exposure time was used.
    You can read the FITS header in software that can open FITS images.
    Accuracy however highly depends on what time source was used. Some 
    (professional) CCD cameras are equiped with GPS and get a very accurate time 
    stamp directly from GPS. But if this one is synchronized by some other means 
    (e.g. by the pc attached to the camera), it all depends on what they used for 
    that and how accurate it was (basically: how accurate the PC clock is kept synched).
    If this same telescope is used for accurate astrometry on asteroids and comets, 
    the timestamp in the FITS header should be fine (as that kind of astrometry 
    demands good time keeping). If it is just used for pretty pictures, I would 
    however not necessarily trust it.
    - Marco
    Kevin Fetter schreef op 26-11-2013 15:34:
    > What the person at slooh replied awhile ago, when I asked about the system.
    > We take a series of exposures during a mission and each exposure's time
    > hack is when that image is written to the database.  So the simple
    > answer is that the time represents the end of the exposure.
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