Magnitude estimates on Heavens-Above

From: Anthony Ayiomamitis (
Date: Mon Apr 23 2001 - 11:18:17 PDT

  • Next message: Rik Hill: "Re: Magnitude estimates on Heavens-Above"

           Has anyone confirmed the magnitude estimates provided by Heavens-Above? As much as I love and use the site, I get serious discrepancies between its magnitude estimates for the
    ISS as well as almost all Iridium flares.
           Tonight I managed to get six photos of the ISS-STS100. Heavens-Above predicted a magnitude of -0.4 but I am convinced it was much higher. I would estimate at least -2 and
    perhaps even higher.
            I had a predicted pass at 20:40 (UT+3) including a pass  within 0.6 degrees of alpha-UMa and another within 0.6 degrees of epsilon-Vir. I did not have sufficient darkness to
    locate either of these two reference points (I could have used another 10-15 minutes) but thanks to some very good alignment between my finder scope and camera attached at prime
    focus, I was able to track manually (with a CG-14!) using the finder scope, setting slightly ahead of the ISS-STS100 and rushing to the camera viewfinder to prepare for a photo. I
    managed to get six photos in the space of about two minutes where the object was at a distance of 445 to 659 km (speak about a nice close distance!).
            All photos were taken at 1/125th sec using Fuji ASA 800 film. I hope to have it developed later this week and will follow-up with a URL if any of the photos do materialize.
            In hindsight, I should have done away with the focal reducer given that I was to track manually using the finder scope.
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