Video Astrometry

From: Derek C Breit (
Date: Tue Mar 31 2009 - 17:10:39 UTC

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     From Dave Herald...
    Over the last 5 years, precisely timed video has matured into the preferred
    approach to recording observations of asteroid 
    occultations. The passage of 2009 DD45 on 2009 March 2 was noteworthy as two
    observers independently recorded the asteroid on 
    video with the aim of obtaining astrometric positions. Significantly, the
    astrometric positions derived from the videos had a 
    positional accuracy comparable with usual CCD astrometry. Most importantly,
    the time associated with each position was determined 
    to a far greater precision than traditional CCD astrometry. [It was
    subsequently determined that the positions reported from 
    Siding Spring required a correction of 0.375 secs; corrections of over 1
    second were indicated for some other observatories.]
    For precise astrometry of fast-moving objects (that is, moving faster than
    100"/minute) precisely timed video provides a number of 
    advantages over normal CCD astrometry - with the advantages increasing as
    the rate of motion increases. Recognising that most 
    observers involved with astrometry have little knowledge of video
    techniques, and that video observers have little knowledge of 
    astrometry, I have put together a Video Astrometry guide. That guide is now
    available on the web site of the Minor Planet Center. 
    On the CBAT/MPC/ICQ index page, it is the 'Documentation' under the new
    heading 'Video Observers'. The direct link is:
    You will also see a link to 'Script for determining mini normal places'. The
    script has been written by the MPC to combine 
    positions spread over an interval of less than _two seconds_ into a single
    position. Its use is essential for video astrometry of 
    fast moving objects.
    The guide is a 29 page document detailing the hardware, software, and
    processing (including normal positions) required to obtain 
    an astrometric observation using video. As referenced in the MPC 'What's
    New' document:
    " A new web service allowing video observers to derive the mini normal
    places needed for submission. Documentation (PDF, 660KB) on 
    using the service is supplied and should be considered mandatory reading.
    [2009 March 30]"
    As I state in the guide, I would like to acknowledge the following people
    who have critiqued or otherwise assisted in putting the 
    guide together.
    John Broughton (who also suggested the possibility of performing video
    astrometry on 2009 DD45 on an internet group.)
    Gerhard Dangl
    Dave Gault
    Bill Gray
    Rob McNaught
    Hristo Pavlov
    Herbert Raab
    Gareth Williams
    Dave Herald
    Canberra, Australia
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