Re: I saw ISS!

From: Patrick Schmeer via Seesat-l <seesat-l_at_satobs.org>
Date: Mon, 6 Apr 2020 17:26:26 +0000 (UTC)
 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-l
Received 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