Re: Tycho-2 Catalog

From: Mike McCants (
Date: Mon Feb 14 2000 - 10:59:03 PST

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    David Brierley wrote:
    >For those of you who haven't heard, the Tycho data from the ESA
    >Hipparcos satellite has been reprocessed, resulting in a new catalogue
    >called Tycho-2 containing the positions and magnitudes of 2,539,913
    >stars.  It is claimed to have a cleaner cutoff than the first Tycho
    >catalogue, at around mag +11.5.  It comes on a CD-ROM in one
    >uncompressed file of 515Mb.
    A while back I wrote a program to "compress" the SAO catalog of only
    250000 stars into a file of 1MB so that a program (that I call "print near")
    could be used to print relatively inaccurate (0.01 degrees) positions
    and magnitudes for all stars "near" (about 1/2 to 1 degree) a given
    RA and Dec.
    A few months ago I did this for the first Tycho catalog.  The resulting
    file was 3 bytes per star times 1200000 stars = 3.6MB.
    I will probably do this to this new catalog.  2500000 stars times 3 bytes
    = 7.5MB.  I could also apply a magnitude cut-off to get a smaller file.
    Would anyone be interested in this?  Typically only satellites above
    5000 miles move so slowly and are so faint that such a catalog/program
    is needed to determine the observed position.
    If you are interested, probably you should email me directly:
    Mike McCants
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