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This comment to Did nobody in the Astronomy community think 12,000 new satellites in LEO might be a problem? links to Phys.org's New ESO study evaluates impact of satellite constellations on astronomical observations which includes ESO's Areas of the sky most affected by satellite constellations shown below.

It's a fisheye lens view (FOV wider than 180 degrees)looking straight up.

There is an large arc that begins at the bottom of the image (where the elevations of 20 and 30 degrees are deonted) and extends upward and toward the left. It looks like it could be a circle about the anti-lunar point since the moon is also seen on the right side slightly above center.

Question: What is happening here? Is this an atmospheric effect of scattered moonlight? If so, what causes such a sharp transition in the amount of scattered light? Does this have a name?

the night sky at ESO's Paranal Observatory around twilight, about 90 minutes before sunrise Crediti: ESO/Y. Beletsky/L. Calçada

This annotated image shows the night sky at ESO's Paranal Observatory around twilight, about 90 minutes before sunrise. The blue lines mark degrees of elevation above the horizon.

A new ESO study looking into the impact of satellite constellations on astronomical observations shows that up to about 100 satellites could be bright enough to be visible with the naked eye during twilight hours (magnitude 5–6 or brighter). The vast majority of these, their locations marked with small green circles in the image, would be low in the sky, below about 30 degrees elevation, and/or would be rather faint. Only a few satellites, their locations marked in red, would be above 30 degrees of the horizon — the part of the sky where most astronomical observations take place — and be relatively bright (magnitude of about 3–4). For comparison, Polaris, the North Star, has a magnitude of 2, which is 2.5 times brighter than an object of magnitude 3.

The number of visible satellites plummets towards the middle of the night when more satellites fall into the shadow of the Earth, represented by the dark area on the left of the image. Satellites within the Earth's shadow are invisible.

Crediti: ESO/Y. Beletsky/L. Calçada

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  • $\begingroup$ companion question in Astronomy: Which kinds of astronomical observations most need to avoid the Moon being up? $\endgroup$
    – uhoh
    Commented Mar 14, 2020 at 6:00
  • $\begingroup$ I would assume it is an effect of the camera system. For example some shadowing effect of the moonlight since the moon is directly opposed to the arc $\endgroup$
    – Christoph
    Commented Mar 14, 2020 at 9:57
  • $\begingroup$ Could it be that we don't see the Zodiacal light from the Earth's shadow? $\endgroup$
    – Keith McClary
    Commented Mar 14, 2020 at 15:04
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    $\begingroup$ It says on the ESO page: "the shadow of the Earth, represented by the dark area on the left of the image". $\endgroup$
    – Keith McClary
    Commented Mar 14, 2020 at 16:31
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    $\begingroup$ This is from the "Fulldome" (First of 4 pages.) I don't see a shadow in any other images. $\endgroup$
    – Keith McClary
    Commented Mar 14, 2020 at 17:10

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What is happening here? Photoshop!

The number of visible satellites plummets towards the middle of the night when more satellites fall into the shadow of the Earth, represented by the dark area on the left of the image. (emphasis added)

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  • $\begingroup$ yep, I can't imagine that this could possibly not be the answer. Thanks! $\endgroup$
    – uhoh
    Commented Mar 18, 2020 at 0:13

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