Hi, My own "earthshine hypothesis" is of course nonsense. When the ISS enters Earth's shadow, our planet would be still illuminated for an observer at a much higher altitude – but not for the ISS itself. Cees wrote: > To re-iterate; it was new Moon on March 24th, so > with the Sun below the horizon, so was the Moon. Anyway, the new moon would be too faint to cause a noticeable effect. > Hence your reasoning also suggests that city lights > are the remaining option. This option can also be tested. How bright you see the ISS in Earth's shadow would depend on the cloud cover above the bright cities (of course your view of the ISS should not be blocked by clouds). The moonlight option (around full moon in particular) is still valid (for many of my own sightings, not for Cees'/Cees's observation). Regards, Patrick ------- Am Montag, 6. April 2020, 15:24:23 MESZ hat C. Bassa <cgbsat_at_gmail.com> Folgendes geschrieben: Hi Patrick, On Mon, Apr 6, 2020 at 3:08 PM Patrick Schmeer <pasc1312-seesat_at_yahoo.de> wrote: > I still think Cees' city lights hypothesis is wrong. I politely disagree. In my earlier post, I already ruled out your first two hypotheses; 1) Earthshine and 2) moonlight for the 22:53UTC observation on March 23rd. Here is the observation I posted earlier: https://i.imgur.com/zws7dQz.png To re-iterate; it was new Moon on March 24th, so with the Sun below the horizon, so was the Moon. The plot at https://imgur.com/a/lz7hROz shows the location of ISS above the Earth. The red line indicates the terminator, and the 3 blue lines on the dark side indicate the loci of civil (-6 deg solar altitude), nautical (-12 deg) and astronomical (-18 deg). Hence, almost the entire footprint of the ISS (gray circle) is located deep at night; only a small bit of it near Iceland overlaps with locations between nautical and astronomical twilight. This essentially rules out Earthshine. You yourself mention that artificial lights on board ISS can be ruled out. Hence your reasoning also suggests that city lights are the remaining option. It is interesting to note that at 22:53UTC, ISS was at 60 degrees altitude from Paris, also known as the "city of light". Furthermore, my observations showed that ISS was fainter around 22:56UTC when it was above the Alps, where there are significantly less cities. Regards, Cees _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-lReceived on Mon Apr 06 2020 - 12:27:26 UTC
This archive was generated by hypermail 2.3.0 : Mon Apr 06 2020 - 17:27:26 UTC