Thread by @cgbassa

This is the impact of a ~1600 satellite @SpaceX #Starlink constellation for a location at latitude 52 degrees. At any time, about 84 satellites would be above the horizon. During twilight and the entire summer, up to 15 of those visible (sunlit and above 30 degree altitude).

These plots assume 53 degree inclined orbits at 550 km altitude, with 24 evenly spaced orbital planes, each having 66 #Starlink satellites. The total constellation would have 1584 objects. This is the initial @SpaceX plan for #Starlink.

cc @planet4589 @Alex_Parker @markmccaughrean @AstroKatie

At 52 degree latitude, these 550 km orbits are illuminated throughout the night from May to mid-August. During those summer nights #Starlink satellites will be visible all the time.

But even in the spring, autumn and winter, around half a dozen #Starlink satellites will be visible at anytime upto 3 hours before sunrise and 3 hours after sunset. Depending on how bright they end up being, this will have a drastic impact on the character of the night sky.

For locations at lower latitudes, the situation is only slightly better. At 34 degree latitude, say Los Angeles, up to 10 #Starlink satellites will be visible during twilight. At those latitudes the satellites will be invisible for only 4 hours in typical a summers night.

It's unclear what this would mean for a 12000 satellites, as the details of their orbits are not known. A rough guess would be to multiply these numbers by a factor of 7 (12000/1600). So around 70 to 100 satellites visible during twilight at any time and any location!

For @markmccaughrean. Here's a plot for the case of 7500 @SpaceX #Starlink satellites at 340 km altitude. Here, I assumed 75 orbital planes with 100 satellites each. There'll be around 40 sunlit and above 30 degrees elevation at any time during twilight.