ISS and the eclipse

Whilst running a simulation of the sky as seen from Side, Turkey at
the time of the eclipse on the 29th, using Starry Night, I noticed
that ISS was in the sky at the time of totality. In fact, it was shown
to pass very close to the zenith 20 seconds before the start of
totality. This set me thinking as to whether it would be visible. The
satellite itself would, of course, only be illuminated by a 90 percent
or more eclipsed sun and the phase angle (sun - satellite - observer)
would be large, thus reducing the brightness still further.
The orbital elements of the satellite were for epoch 21st March, thus
the timing may vary by a minute or two by the 29th, but ISS will
certainly cross from north-west to south-east at or about the time of
totality.
Observers in the area might find it worth looking out for.
Incidentally if ISS was 7 minutes later, it would fly through the
umbra.

I wondered abot this too but I suspect not as the ISS brightness would
be reduced by the same percentage that the ambient sunlight is reduced,
so the contrast will be similar to a normal daylight pass. There is the
possibility of catching it passing over the eclipsed sun however.

http://eclipse.astronomie.info/2006-03-29/isstransit/

Robin
(Now reduced to using Google Groups since Wanadoo stopped carrying
Usenet)
-----------------------------------------------------------------------------
Robin Leadbeater
54.75N 3.24W
http://www.leadbeaterhome.fsnet.co.uk/astro.htm
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An observer on ISS is never going to see much more than about a 90
percent eclipsed sun, so I thought that an observer on the ground in a
location where the sun is 99 or 100 percent eclipsed would see their
ambient light reduced significantly more than the light they see
reflected off the satelllite, thus making it visible.


Dave W.

On 24 Mar 2006 03:01:47 -0800, "robin_astro"
wrote:

I wondered abot this too but I suspect not as the ISS brightness would
be reduced by the same percentage that the ambient sunlight is reduced,
so the contrast will be similar to a normal daylight pass. There is the
possibility of catching it passing over the eclipsed sun however.

http://eclipse.astronomie.info/2006-03-29/isstransit/

Robin
(Now reduced to using Google Groups since Wanadoo stopped carrying
Usenet)
-----------------------------------------------------------------------------
Robin Leadbeater
54.75N 3.24W
http://www.leadbeaterhome.fsnet.co.uk/astro.htm
-----------------------------------------------------------------------------

wrote:
An observer on ISS is never going to see much more than about a 90
percent eclipsed sun, so I thought that an observer on the ground in a
location where the sun is 99 or 100 percent eclipsed would see their
ambient light reduced significantly more than the light they see
reflected off the satelllite, thus making it visible.


Dave W.


Ah yes, of course. I was assuming the ISS and observer would be equally
illuminated which obviously need not be the case.

Robin

On 24 Mar 2006 09:10:23 -0800, "robin_astro"
wrote:


wrote:
An observer on ISS is never going to see much more than about a 90
percent eclipsed sun, so I thought that an observer on the ground in a
location where the sun is 99 or 100 percent eclipsed would see their
ambient light reduced significantly more than the light they see
reflected off the satelllite, thus making it visible.


Dave W.


Ah yes, of course. I was assuming the ISS and observer would be equally
illuminated which obviously need not be the case.

Robin

Well, I didn't see it. One or two other things to look for - shadow
bands, Baily's beads, moon's shadow approaching, diamond ring,.....

Dave W.

David Wood wrote:
On 24 Mar 2006 09:10:23 -0800, "robin_astro"
wrote:


wrote:

An observer on ISS is never going to see much more than about a 90
percent eclipsed sun, so I thought that an observer on the ground in a
location where the sun is 99 or 100 percent eclipsed would see their
ambient light reduced significantly more than the light they see
reflected off the satelllite, thus making it visible.


Dave W.


Ah yes, of course. I was assuming the ISS and observer would be equally
illuminated which obviously need not be the case.

Robin


Well, I didn't see it. One or two other things to look for - shadow
bands, Baily's beads, moon's shadow approaching, diamond ring,.....

Dave W.
In the ISS you dont need the moon to eclipse,
any small coin can replace the moon and you
can have an eclipse whenever you want.
I seem to remember that there have been
satelites doing just that to monitor the
sun's fotosphere.

Sjouke Burry wrote:


Dave W.
In the ISS you dont need the moon to eclipse,
any small coin can replace the moon and you
can have an eclipse whenever you want.
I seem to remember that there have been
satelites doing just that to monitor the
sun's fotosphere.

I am not sure if that's the case is it? (At least I have not seen it
demonstrated) Although you get rid of atmospheric scattering,
diffraction effects around an object so close will still give problems
I think. Even the coronagraphs on SOHO (The satellite you are refering
to) cannot image the corona close in.

http://sohowww.nascom.nasa.gov/hotshots/2006_03_29/

Robin