Are These Satellite Trails?

Ed Beshore:
Images one and three have multiple parallel trails -my first reaction is that these are  set of SpaceX Starlink or similar communications satellites. These will become increasingly common with time. 

Ed

*I guess shooting much later in the evening might reduce the sun's reflection on the increasing number of satellites orbiting the planet.

How do experienced astrophotographers deal with these nuisances? Is PixInsight the best software for removing them? 

I hope that as the number of satellites continues to increase the software will get better and better at removing them.

Pixinsight and other software can be pretty effective at removing these. Image integration in PI can reject anomalously high pixels using a number of algorithms (sigma clipping, for instance).

One trick is to take enough subs that you might be able to eliminate those frames entirely. In the case of M42, you probably want to keep your subs short anyway to avoid blowing out the bright center of the nebulae. That means you can have plenty of subs and throwing a few away are usually not a problem.

Good luck, Ed

They are geostationary satellites. Orion is in the background of their orbits as seen from mid northern latitudes.

Ed Beshore:
Ed Beshore#19 minutes ago·  4 views
Tim McCollum:
They are geostationary satellites. Orion is in the background of their orbits as seen from mid northern latitudes.


Hi Tim -

If they are geostationary why are they moving in straight lines?  I would think that geostationary sats would be just that - stationary. This is why ground stations don't have to track them, they can just point at fixed locations in the sky.

Ed,

You are correct in that if you point your telescope toward a geostationary satellite, it will not appear to move in the FOV of a stationary mount, however, all of the background stars, nebulae, etc. will move.  The OP was taking a shot of the Orion Nebula clearly using a tracking mount, so the nebula appears stationary, but when tracking, anything that was stationary, for example any foreground tree or even a geostationary satellite, would move in a straight line out of the FOV over time. 

To demonstrate, point your untracking telescope to a geosynchronous satellite and it will indeed stay stationary while all the stars move through the FOV.  Now turn on the tracking - the stars stop moving and the geostationary satellite moves out of the FOV in a straight line.

Ron

Ed Beshore:

Tim McCollum:
They are geostationary satellites. Orion is in the background of their orbits as seen from mid northern latitudes.

Hi Tim -

If they are geostationary why are they moving in straight lines?  I would think that geostationary sats would be just that - stationary. This is why ground stations don't have to track them, they can just point at fixed locations in the sky.

This gets brought up quite a bit and is an easy mistake to make.

Geostationary satellites are fixed to a point on the ground. Hence the name. When imaging, you are fixing your camera/scope to a very distant point in the sky. The earth and the satellite in geosynchronous orbit are rotating together. This is why you see Orion rise in the east and then set in the west. It isn't really moving (well, it is, but for the sake of this discussion, its movement is so inconsequential, it is 0)... it is you and the earth and those satellites that are rotating at about 15 degrees per hour.

Here's a fun experiment for you to try. Find the coordinates for a geostationary satellite. Slew your mount to those coordinates, but do not start tracking. Now, take an image... maybe a 3 minute exposure. You'll see plenty of stars trailing across your image... but that satellite will stay pinned right there in the center. Turn on tracking and take another 3 minute exposure. The stars will be points, but that satellite will streak across your image.

Many a night I have been looking at Orion with just my eyes and see a flash that repeats about every 13 seconds then train my binoculars on it.
What I was seeing was a geostationary satellite creating a sun glint as it was spinning. Most all geostationary satellites are spin stabilized.
The actual satellite core is de-spun so as to keep its antennas pointed at a fixed spot on the Earth, only the solar panels spin.
This bright glint only last for about a minute as the sun angle changes.
Tim