TLE Information, Please

From: amstuart (
Date: Sat Feb 07 2009 - 20:44:17 UTC

  • Next message: Ralph McConahy: "Re: TLE Information, Please"

    I would like to learn how to be assured that I am looking at the <latest>
    TLE information for the ISS. I use Heavens-Above and Space-Track to load TLE
    data into Software Bisque's TheSky in order to plan an imaging session. I
    look at the transit path and choose a good star to sync on and refine my
    GOTO's until the transit path crosses my CCD sensor.  Instead of manually
    guiding my LX200 with ToUcam attached, I am going to place my tiny 7.9' x
    5.9' FOV such that the ISS transects the rectangle as it transits my local
    This morning (8 AM EST), I loaded the epoch 09037.82898148 TLE from H-A.
    I just went toSpace-Track  (3:30 PM EST) and loaded the last 5 TLE's.
    Since I am using SAO 75883 as an easy star to sync on as the ISS transits
    and then culminates at ~89* ALT, the different TLE's have me placing my CCD
    chip east and west of SAO 75883 depending on the TLE used. Since this is a
    cat-and-mouse approach to capturing a mere 3 frames (30 fps) as the ISS zips
    past the sensor, I need very accurate placement. Three arc-minutes off east
    or west will surely cause me to miss the ISS transiting my sensor. Is there
    a certain time of day that the ISS TLE becomes the "latest" and most
    "accurate"? If the pass is at 18:14 EST, when should the latest TLE be
    Thank you.
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