Ted, 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 aavso.org. 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 http://mailman.satobs.org/mailman/listinfo/seesat-lReceived on Wed Feb 26 2020 - 08:35:05 UTC
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