Re: Magnitude estimates on Heavens-Above

From: Anthony Ayiomamitis (
Date: Mon Apr 23 2001 - 11:50:24 PDT

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

    Hi Rik,
          From what I recall, an order of magnitude translates to a factor
    of about 5.7x. As a result, if Heavens-Above is off by 1-2 magnitudes,
    we are really talking about a factor of 5.7 to 32.5 ... personally I
    would consider this a serious error. My experience tonight was at least
    a couple of magnitudes off. In fact, I would go further and claim that
    it was probably off by about 4 magnitudes (Venus a couple of months ago
    at -4.4 had similar magnitude to tonight's pass).
          There have been occasions when I have not bothered pursuing photo
    opportunities with the ISS and shuttle due to a low predicted magnitude
    from Heavens-Above. From now on I will take a more aggressive approach
    as I may be foregoing opportunities that I should be pursuing.
           Ditto for iridium flares as I have seen differences of the order
    of 3 to 4 magnitudes between Rob's program and Heavens-Above.
    Rik Hill wrote:
    > I too have noticed discrepencies and mentioned them on this list.
    > Since I am often doing visual photometry on variable stars on the
    > same night I have a pretty good idea what a given magnitude looks
    > like. While I would expect variations of 1-2 mag. just due to
    > presentation of a satellite, still on several I have noted 4 mags.
    > With ISS and STS's the variations can get big and the more junk
    > they stick on to the ISS the more that will probably increase. Right
    > now I've been trying to get video in one of my telescopes of these
    > two and have noted some variations from predicted brightnesses, but
    > still they were the brightest moving target in the sky!
    > -Rik
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