Re: Satellite lunar transit

From: Bruno Tilgner (
Date: Sat Aug 18 2001 - 08:41:41 PDT

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    Mark Henning-Lee wrote:
    > You might also try a transit in front of the Sun. As the Sun shines
    > much longer than the the Moon the probability of such an event is
    > proportionally larger.
    >Surely not?
    >The sun and moon have almost the same apparent size of 0.5 degrees.
    >On average, each of them is above the horizon 12 hours a day.
    >Seems like the same transit probabiltiy to me!
    You are absolutely right, at least over a period of 18.6 years.
    What I should probably have said is that the Sun shines longer than
    the Moon *during the average amateur's observing hours*. Lunar
    transits have the habit of occurring at uncomfortable hours in the
    middle of the night. Lunar transits during daytime must be discarded
    if the Moon is too close to the glare of the Sun. Finally, if the
    transit occurs too long before or after Full Moon it may be unobservable
    because it crosses the dark part of the Moon.
    All in all, solar transits are much more likely to be observed than
    lunar transits, and this is confirmed by the record of observations.
    I know of only two verifiable and documented solar transit observations:
    one by Ron Dantowitz as described in the April issue of SKY & TELESCOPE,
    the other one by a Belgian observer on 25 June which has not been
    published so far but of which I have a copy of the video recording.
    On the other hand, I am not aware of any documented lunar transit
    by a dark satellite.
    Bruno Tilgner
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