“I’m not aware of any geosynchronous satellites spoiling any of my photos, but I’ve had an occasional unexplained streak which I usually attributed to an airplane. They typically have an oscillating intensity across the image, and there has been some debate as to whether it could be a rotating satellite. Do satellite rotate? It would be like it would make it difficult to aim an antenna that way. I recently saw someone on Twitter who purposely imaged some geosynchronous satellites. They are pretty fair out there at 22K miles to they weren’t very bright.”

I would expect that passing airplanes would have red flashing lights, an attempt to be seen by other aircraft, so if your unexplained streaks have little red pearls, then those may be planes.

Spin stabilization is not as common for satellites as it used to be, and for those satellites the antennas are either designed to account for the spin or are mounted on de-spun platforms on the satellite. All the geostationary Earth orbit (GEO) satellites that I know of are three-axis stabilized, pointing to the Earth at all times. Dead satellites and spent upper stages tend to tumble, which may account for the oscillating intensities.

I once went to an overnight astronomy viewing party on top of a short mountain, and one of the guys had his telescope pointed to something that was on the far side of the GEO orbit. Every once in a while a string of white dots would cross the field of view. These were geostationary satellites.*

GEO satellites are also located at specific longitudinal locations. The broadcast frequencies that they use determine how far apart they must be from other satellites that use the same frequencies, sometimes 1 degree, sometimes 2-1/2 degrees, so at 1/2 degree increments (as you know, about the width of the Moon) you may find half a dozen-ish of these satellites fairly close together. My recollection is that 1/2 degree is two minutes.
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* For readers unfamiliar, the geostationary satellites still orbit the Earth, which is why they do not fall down to the ground. This means that they appear stationary to we observers on Earth, but they still move relative to the background stars. Our satellite TV antennas can hold one position and continuously listen to a satellite. From our point of view, or reference frame, the stars move around the Earth, just like the Sun and the Moon, and the GEO satellites are stationary (geo = Earth, stationary = not moving relative to a viewer on that Earth).

For astronomical viewing, many powerful telescopes are counterspun relative to the Earth’s rotation, which is the purpose of those domed observatories, so that as we view the stars, they remain stationary in the eyepiece. However, that means that the GEO satellites appear to move across the eyepiece as we view our stars. It is all a matter of reference frame and whether or not it is moving. We live on a rotating reference frame. Don’t get dizzy thinking about it, you may fall from your chair.

https://spotthestation.nasa.gov/

#1: I agree. My understanding is that Starlink is purposely in low orbit in order to reduce transmission delays. I just looked up Starlink’s altitude is about 340 miles, while ISS is 254 miles. Hubble is 332 miles. Geosynchronous orbits are 22,236 miles.

#2: Correct. The air isn’t very steady right after sunset and telescope is cooling down. Most amateur astrophotographers will be polar aligning during this time, anyway.

In the olden days when I started astrophotography with film, we’d take very long exposures that could be up to 2 hours. You’d hope that you don’t get any gusts of wind or someone walking near your scope which could ruin your photo. With modern digital cameras, you typically make several short exposures of 5-10 minutes which are stacked. You can simply throw out any bad ones.

I remember the Iridium flares. They were amazing!

Airplanes are definitely a nuisance, and they can spoil an image at any time of the night.

I’m not aware of any geosynchronous satellites spoiling any of my photos, but I’ve had an occasional unexplained streak which I usually attributed to an airplane. They typically have an oscillating intensity across the image, and there has been some debate as to whether it could be a rotating satellite. Do satellite rotate? It would be like it would make it difficult to aim an antenna that way. I recently saw someone on Twitter who purposely imaged some geosynchronous satellites. They are pretty fair out there at 22K miles to they weren’t very bright.

However, he apparently does not read this site often enough to have seen my questions.

Jason Lewis,
Would you be able to answer them? Some seem to be already answered by your comment, above:

1) Don’t these Starlink satellites shine and spoil the photographs only shortly after sunset and shortly before sunrise? The sun does not shine on them once the satellites are in Earth’s umbra. Doesn’t this give several hours of Starlink-free viewing and photography? When I go satellite watching, I am limited to observations at these times when the satellites are not yet in Earth’s umbra.

2) Aren’t the times that these satellites are not yet in Earth’s umbra mostly times when it is not yet dark enough to do good time-lapse photography? Since doing this astrophotography requires long exposure times, don’t your photographs begin toward the east, where the satellites are already in the umbra, so that as your camera moves toward the west, the satellites will already be in the umbra when your camera gets there? When I go satellite watching, I observe that the satellites first lose their visibility toward the east, then this loss of visibility drifts westward as the evening wears on. In the morning, I imagine, visibility should return toward the east before it does in the west, but when the Sun is about to rise, isn’t it better to not start photographing long exposure times?

3) Don’t large numbers of satellites already pass through your field of view during these same times that Starlink satellites interfere with your viewing? Even before Starlink, when I went satellite watching, I observed many satellites that have yet to enter Earth’s umbra. A quarter century ago, there was the phenomenon with the Iridium satellites when they would occasionally shine brightly during these times as one of their solar arrays briefly would be angled just right with the sun to reflect the light onto parts of the Earth, where viewers could see them as temporary, very bright lights in the sky. It was called an Iridium flare. They looked like flashes in the sky, and photographed as bright streaks. Do they still do this, or are the next generation Iridium satellites doing something different with their solar arrays?

4) Don’t airplanes already fly at night and spoil your photography and viewing with their flashing lights? Don’t these airplanes fly all night long rather than only near sunset and sunrise? They do in my area. Airliners, cargo planes, military aircraft, and the occasional nighttime private plane. Despite being inside Earth’s umbra, when passive objects would not be lit up, these airplanes are actively lit with “see and be seen” navigation lighting. Don’t these planes spoil your photography even after Starlink and the other satellites enter the Earth’s umbra and are no longer visible? When I go satellite watching, I see all kinds of airplanes in the sky during the times that the satellites are visible, before they enter the Earth’s umbra.

5) How do you photograph areas of the sky in which geostationary satellites would interfere with the photographs. These satellites only spend about 2% of their time inside Earth’s umbra (a greater percent of each orbit within a few weeks of the equinoxes, and no time spent in the umbra for several weeks on either side of the solstices).

6) Why are the Starlink satellites singled out? Each year, literally hundreds of other small satellites are taken to low Earth orbit, yet these others are not the subject of complaints for spoiling photography of the stars. Neither are OneWeb satellites. Will the Kuiper constellation likewise not be the subject of complaints?

But if there is a threat it is during the shorter defined astronomical period of darkness, and it is from the actual obscuring of targets by satellite bodies themselves. I believe the impact of this could be difficult to detect, because while the data gathered could be modified, no visual indication of the modification within the data would necessarily occur.

A natural reaction would be to say that average sized satellites would be incredibly unlikely to interfere with observations. That may true or not, but it is inevitably true that with the advent of super-heavy-lift launchers, the frequency of very large satellites will increase.

No big outcry

Jason Lewis: Fascinating. Based on what you write, the claims of the astronomy community are even more bogus than I imagined.