Satellite pollution

[gregl]

We all know the problems satellites are causing. Today's Astronomy Picture of the Day shows it well:

https://apod.nasa.gov/apod/ap220614.html

[Richard]

Yes and its going to get worse year by year , seems everyone is so concerned about polluting Earth and forget about this!

[Johnny Carter]

That is mind boggling, always growing and always causing more potential problems.

[JayTee]

Stunningly horrible.

[Makuser]

Hi all. Yes and it IS getting worse. Most of the launches that I photograph here from my backyard are for the SpaceX/Starlink satellites and very few are for the ISS missions. Here is another link/article with many photos (some are already a couple of years old) on this situation, at:
https://www.astro.princeton.edu/~gbakos/satellites/

[OzEclipse]

I'm no fan of Starlink nor Elon.

However, that photo was posted in a Facebook astrophotography forum a few weeks ago. The group rules require disclosure of techniques.

If I recall correctly, this is not a single image and is the result of many many frames. He extracted the satellite streaks from the sequence of images and overlaid them on a short stack of nightscape images. Had he stacked them conventionally, they would have disappeared.

I have been noticing many more satellites in the 1 degree field of my 18" telescope when examining various objects. Oddly, last night, I did not see one.

Joe

[Ylem]

Looking at that first image, I can only think of SkyNet in the Terminator movies.

[TCampbell]

It looks bad and I don't know any astrophotographers who haven't had numerous satellites photo-bomb their shots. HOWEVER there are a few things that are helpful to know.

1) The satellite shows up because it is reflecting sunlight. When it is only recently become dark it means *you* can be in darkness, but a satellite in orbit above you is still in sunlight. Later in the night ... even the satellites are in total darkness. This means there are times when you are not likely to see any satellites.

An exception to this applies to your latitude. In the northern-hemisphere summer, depending on your latitude, there may *never* be a time in the night when satellites wont be visible. Currently (since the solstice was just yesterday) the entire arctic circle is in full sunlight. That's a latitude of 66.5°. If you lived at a latitude of say ... 50° ... you'd be able to see satellites anytime of the night.

2) FORTUNATELY there are image integration techniques which magically erase these satellite trails. If you capture enough images (e.g. 10+) you can use integration techniques that use clipping algorithms to detect anomalous pixels. e.g. if 9 of 10 frames say the pixel is black but 1 in 10 says the pixel is white, the software can analyze the pixel in the aligned frames and determine that the statistical mean is a lot closer to black and therefore the frame that says it is white must be an outlier. It can reject just the bad pixels (but keep all the good pixels in that frame) and replace the bad pixels with the mean of the corresponding pixel in the 9 remaining frames.

This technique works much better than integration by "averaging" -- where the satellite trail would get dimmer ... but not completely eliminated. In these statistical stacking methods, the bad pixels are completely eliminated and you don't have to throw out the frame just because a satellite photo-bombed it.

[Baurice]

One thing I hate is trying to differentiate satellite trails from meteor trails. I have found that, by using 6 seconds exposure, the satellite trails usually appear on successive images, whereas a meteor trail does not.

[Baurice]

I'll be back!

The next road to ours is called Skynet Drive.