RE: Some errors in Heavens Above's prediction on Iridium Flares

From: Matson, Robert (
Date: Wed Jul 31 2002 - 21:04:38 EDT

  • Next message: Tom Wagner: "Re: Some errors in Heavens Above's prediction on Iridium Flares"

    Hi Shea,
    > Recently, I've found something wrong in Heavens Above's prediction
    > on Iridium Flares. ... Most of them are right, but the Alt. is
    > wrong. The observation is that Alt. is nearly 90 [versus 60
    > observed]. The error is roughly 30, so great!
    You may be surprised at just how high in the sky the zenith
    really is -- it is not a comfortable direction to be looking
    while standing, and consequently most beginning observers
    overestimate all elevation angles -- with increasing errors
    as the angle increases.  Here is a typical altitude angle
    conversion table I use for "translating" beginners' reported
    altitude angles:
    Reported  Actual
      Angle    Angle
    --------  ------
        10       7
        15      10
        30      20 
        45      30
        60      45
        80      60
        90      70
    Try testing yourself with some bright stars that are well above
    the horizon -- guess their altitude angles and then use one
    of the many planetarium programs out there to see how close
    you were.  You may be surprised by the results.
    Best wishes,
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