Starlink brightness observations of Russell Eberst posted by Ted Molczan

From: Anthony Mallama via Seesat-l <>
Date: Wed, 26 Feb 2020 09:33:46 -0500

Thanks for sharing Russell Eberst's magnitude data. I found that the
average 1,000 km magnitude for the satellites at the final 550 km altitude
is 6.8. When that is adjusted to 550 km it becomes magnitude 5.6.

Your plot shows a moderately weak correlation between brightness and phase
angle (again for the satellites at the final 550 km altitude). So, these
data do not indicate a very pronounced backward or forward scattering of
sunlight - more like a diffuse scattering. Additional data at high and low
phase angles would provide a more definitive result though.

Since Starlink satellites themselves are shaped like a table top, I would
expect to see a fairly strong dependency of distance-corrected brightness
on elevation above the horizon. The satellites are seen face-on (presumably
brighter) when overhead but edge-on (fainter) when near the horizon, if I
understand their orientation correctly.

There could also be a relationship between brightness and the azimuth
difference between satellite and sun - due to scattering. (Similar to phase
angle though not quite the same.) Altogether, the brightness model might be
fairly complex.

Question: If the satellite elevation and azimuth turn out to be important,
can those quantities be determined for past observations? I ask because
positions from TLEs become inaccurate pretty quickly. So, I'm wondering
whether az and el should be recorded at the time of observation.

In my opinion, the brightness of Starlink satellites is an important issue
(ask any astronomer) and a major way in which we observers can contribute
to our field of study. Anyone who wants to make visual brightness estimates
can find instructions for stars at The same method can be
applied to satellites.

Lastly, I can send you a spreadsheet with my first 20 magnitude
observations if you want to include them in your analysis. They're not in
the format you're using though as they include az and el.

Best regards,
Tony Mallama
Seesat-l mailing list
Received on Wed Feb 26 2020 - 08:35:05 UTC

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