Re: STS-114 / ISS Double Sun Transit

From: Gerhard HOLTKAMP (
Date: Mon Aug 01 2005 - 14:17:08 EDT

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    Stephan Szyman wrote:
    >anyhow,  I'm curious,  what equipment or filters were you utilizing to 
    >observe the sun during the transit?  did you have  5 scopes?  or were you 
    >wearing some special glasses or something?
    I've used a 3 inch Apo-refractor with an ND5 glass sun filter, just what I 
    normally use for sun observations. We also had a 5 inch refractor and two 8 
    inch SCTs (one was used for the camera) with ND5 sun screen foil for visual 
    observations and ND4 foil for the camera (to allow higher speed). The ISS is 
    so small that you do need a telescope to observe the transit. Solar eclipse 
    glasses or so won't do. The magnification I use for such observations depends 
    on the elevation of the sun at the time. With a very high sun the transit is 
    short (e.g. 0.5 sec) in which case my eyes find it easier to see something 
    with a 40x magnification. If the transit is slower (which happens at lower 
    sun elevations) I use higher powers. But this is something very individual to 
    each observer I guess.
    >I'd sure like to try to see a solar transit of the station sometime.  I saw 
    >the venus transit and it was really wicked.
    Solar transits of the ISS are quite frequent. If you don't mind travelling 
    some 30 miles or so you should expect 2 or 3 transits a month at your 
    latitude of 41.7. If you live close to 50 latitude as I do you seem to get 
    them even more often (at least during the summer). Two years ago I was able 
    to observe 4 transits within one month without even leaving the house!
    Clear skies (day and night)
    Gerhard HOLTKAMP
    Darmstadt, Germany
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