RE: I saw ISS!

From: Thierry Legault via Seesat-l <>
Date: Mon, 06 Apr 2020 13:42:07 +0200

I'm thinking of the Moon too. I can illuminate 
the ISS, even if it's under the horizon (just 
like the Sun illuminates the ISS before sunrise or after sunset).

Rough calculation: the magnitude of the full Moon 
and the Sun differ by 14, therefore the ISS 
illuminated by the full Moon should be 14 
magnitude dimmer than -4 (the maximum magnitude 
of the ISS in sunlight), ie mag +10. For a star, 
mag +10 is accessible to a 40mm telescope only. 
Of course, the ISS is not punctual and a larger 
telescope would be necessary (because its light 
is spread over a larger apparent area), but I 
think that it's still accessible to an amateur telescope.

For those of you who have catched the ISS in the 
shadow of the Earth, it could be interesting to 
know what was the situation of the Moon at that moment.


At 18:27 31/03/2020, John Franke via Seesat-l wrote:
>As a satellite approaches the shadow of the Sun, 
>the sunlight is taking a longer path through the 
>Earth's atmosphere and more blue light is 
>scattered than red light, the result is redder 
>sunlight, much the same as for sunsets. When the 
>shadow edge is far below the satellite, the 
>light does not pass through any of the Earths 
>atmosphere and hence the sunlight is whiter. 
>John > On March 31, 2020 at 11:02 AM Daniel 
>Hampf via Seesat-l <> 
>wrote: > > > Hello Cees and everyone, > I found 
>this really interesting, so I pointed my 
>tracking telescope at the ISS on a pass last 
>Tuesday. I could indeed follow it for more than 
>a minute into the Earth shadow, then I lost it 
>due to poor tracking. I hope to do this again 
>soon. > I recorded the brightness and colour 
>index of the ISS during the pass and uploaded it 
>here: > > As 
>expected, the brightness decreases by several 
>orders of magnitude when it goes into the 
>shadow. Interestingly, the colour index jumps 
>from blue-ish to red-ish after it's reached the 
>shadow. However, from a single pass it's hard to 
>say if that is actually an effect of the shadow 
>a rather of another viewing angle onto the 
>structure. > I'm still quite puzzled as to where 
>the light is coming from. Cannot quite believe 
>it's the city lights, but I don't have a much 
>better idea either. Will be interesting to hear 
>what other people think. > Thanks for this 
>inspiration! > Best, > Daniel > > > > 
>-----Ursprüngliche Nachricht----- > Von: 
>Im Auftrag von C. Bassa via Seesat-l > Gesendet: 
>Dienstag, 24. März 2020 00:27 > An: Seesat-L > 
>Betreff: I saw ISS! > > This subject used to be 
>hot on SeeSat-L back in 1998, but this evening > 
>I saw ISS where I did not expect to see it -- 
>while ISS was in the > shadow of the Earth! > > 
>I only noticed that my camera had captured ISS 
>while processing the > results. I was very 
>puzzled why ISS was not much much brighter. 
>Only > after checking the time of the 
>observation (21:15UTC), did I realize > ISS was 
>already in the Earth's shadow and no longer 
>illuminated by the > Sun. > > At 21:15UTC ISS 
>was only about a minute after shadow entry, so 
>some > stray sunlight may still have been 
>illuminating ISS. Hence, I set up > the camera 
>again for the next pass, that was predicted 
>around > 22:53UTC. Passing close to Procyon, ISS 
>was seen again. Shadow entry > on that pass was 
>at 22:48UTC, so ISS was deep into the shadow. 
>I > re-positioned the camera towards Spica to 
>catch it later in the pass. > While not obvious, 
>ISS was detectable after correcting for the > 
>expected motion and averaging the moved 
>frames. > > I've uploaded my images to this 
>link: > > This 
>clearly highlights the sensitivity of my setup, 
>but also that ISS > is big enough to reflect 
>what must be lights from bright cities while > 
>passing over Europe. > > An unexpected 
>first! >     Cees > 
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Thierry Legault

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Received on Mon Apr 06 2020 - 06:56:04 UTC

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