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Could anyone help me to explain?

This evening I played with a Gen 3 night vision binocular. I spotted a very slow blinking light 5 hours after sunset. I made a 5 minute video, I but can't attach that here. The object was stationary for 2 minutes and then moved around quarter of a degree in 3 minutes. The frequency of the blinking didn't change (1 flash/7 sec). I wasn't able to see it with the naked eye.

As far as I know, balloons (weather or internet) doesn't have lights and the sun was way below the line where reflecting light could cause the flashes. Even if one has lights in the high altitude winds it couldn't stop and then drift again later.

What I think it was a high orbit rotating satellite (because of the blinking). If I'm right two questions remain, how was it in stationary position for a while? (I can imagine an optical illusion too). If I check the high orbiting satellites, the GPS/GLONASS systems could be that high level but those can't blink, they don't have lights and aren't rotating at all.

I played with a Gen 3-D night vision binocular. I spotted a very slow blinking object 5 hours after sunset. The object was stationary the frequency of the blinking didn't change (1 flash/7 sec) during the video. I wasn't able to see it with the naked eye. At 2 minutes I repositioned the camera a little to check if the sensor is playing with me but it wasn’t.

As far as I know, balloons (weather or internet) doesn't have lights and the sun was way below the line where reflecting light could cause the flashes on a rotating(?) balloon. Even if one has lights the high altitude winds would move it for a little.

I checked the geosynchronous satellites can be seen, but only because of the reflecting sunlight on the solar panels, otherwise they have no lights.

The other object is moving through the left side of the screen (at 1:52). According to the speed it is a low orbit satellite(s) but those aren’t traveling side by side. The Starlink is following each other in a line and never on the side.

I'd appreciate it if somebody could help to explain.

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  • $\begingroup$ Does this answer your question? Star like light moving in the sky, what could it be? $\endgroup$
    – WarpPrime
    Dec 9, 2021 at 23:26
  • $\begingroup$ Interesting question! Nicely written, welcome to Astronomy SE. I've posted an answer, but if you can comment further on how certain you are that the object "was stationary for 2 minutes and then moved around quarter of a degree in 3 minutes" and without question did not move steadily for the whole time, and mention if your binoculars are simply image intensifiers for visible or near IR versus thermal IR, that would be great! $\endgroup$
    – uhoh
    Dec 10, 2021 at 9:16
  • $\begingroup$ Geostationary satellites all lie along one line across the sky, directly over the equator, meaning that it's easy to rule that out if it lies somewhere else in the sky. A sky map will show you where this line is $\endgroup$
    – Innovine
    Dec 19, 2021 at 18:41
  • $\begingroup$ can you give us the coordinates for where in the night sky this is, and the specs for the device used? (magnification, light amp, etc.).. #2: did you look at the same location the next night, at the same time? $\endgroup$
    – CuteKItty_pleaseStopBArking
    Dec 19, 2021 at 19:35
  • $\begingroup$ Unfortunately I didn't record the coordinates (around 190 degrees from Geneva,CH) and I didn't take a look later, but it was exactly on ecliptic line. Based on that it should be somewhere over Western-Africa, I will be able to find it if it's really a geostationary thing. The device was a LN-G3-B50 from Luna optics, I used the lowest magnification 6x. $\endgroup$
    – Gergely Szucs
    Dec 21, 2021 at 21:49

4 Answers 4

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Answer: Tumbling satellite in high inclination (>90°) Mid Earth Orbit

I’ll assume your binoculars are tripod-mounted without a motor drive mount since the star field is moving uniformly. Since the field is moving left to right, I assume you are observing from the northern hemisphere, looking toward the equator. Because the path of the stars is down and to the right, the viewing direction is most likely SW. If you are like most binocular/tripod users, you have your binos aimed about 30° above the horizon. Higher elevations need a very tall tripod and a young neck.

Judging by the apparent speed of the stars, your field of view is 5° which is typical for binoculars.

If you are in the US or Europe and looking 30° above the summer SW horizon, you are aiming pretty close to the ecliptic

SW is the best direction to view satellites by sunlight, but 5 hours after sunset would have all LEO satellites in shadow. The edge of the Earth’s umbra is (very roughly) 10,000 km directly overhead in middle latitudes at that time of night, but it is considerably lower in the western sky. Satellites in Mid Earth Orbit could well be illuminated by the sun.

You stated:

The object was stationary for 2 minutes and then moved around quarter of a degree in 3 minutes.

This is incorrect.

The object is moving against the star field at a uniform rate of about 0.30°/min. The object has a uniform motion of 0.15°/min north with respect to the viewing field throughout the video.

So, if the object is in space, it is moving (against the star field) to the SW at 0.3°/min. At an orbital altitude of, say, 20,000 km (typical for GPS satellites), that would be about 6,000 km/hr. Orbital velocity for GPS satellites is 14,000 km/hr. There is a discrepancy between these speeds, but remember the 6,000 km/hr calculations was made using a wooden ruler to measure Sharpie marks on a monitor screen. With some hand waving, the results are compatible with a satellite in a highly inclined MEO orbit. The regular flashes are compatible with a tumbling satellite (which would be in full sunlight from the derived viewing location).

If the object is in the atmosphere, it is moving (in the viewing frame) at about 1°/min to the NE. If the object were at the altitude of commercial airliners, it would be traveling at 10 km/hr which is significantly below the stall speed of fixed wing aircraft , at an altitude incompatible with rotary wing aircraft. A buoyant aircraft could maintain this altitude and airspeed. But why would it?

My best guess is you saw a tumbling satellite in high inclination (>90°) Mid Earth Orbit

This answer is hardly up to SE’s rigorous standards, but the best I can do with a Sharpie. How do I get the marks off my monitor???

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  • $\begingroup$ You don't need to compare orbital speeds. From 0.3°/min you can get directly to an orbital period of 1200 minutes, or roughly 20 hours. Seems to be close to a rather common 24 hour orbit? $\endgroup$
    – asdfex
    Aug 28 at 8:39
  • $\begingroup$ @asdfex ... correct. An orbital period of 20 hours is consistent with a circular MEO. $\endgroup$
    – Woody
    Aug 28 at 22:44
  • $\begingroup$ Is the high inclination a set fact from your analysis? I didn't look in detail, but since the object was seen "exactly on ecliptic line", 15° would match some decommissioned GEO satellites. $\endgroup$
    – asdfex
    Aug 29 at 16:18
  • $\begingroup$ @asdfex ... Geostationary orbits are inclined with respect to the ecliptic. They are coplanar with the celestial equator (and the Earth's equator). The object was moving with respect to the celestial sphere. It would cross the celestial equator at an oblique angle so it could not be geostationary. But if its orbital period was 24hr+/- it could still be geosynchronous. $\endgroup$
    – Woody
    Aug 29 at 16:55
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    $\begingroup$ That's why I wrote "decommissioned GEO", which essentially is a subset of inclined GSO. Looking southwards at 22:00 in December should mean that the ecliptic is only a few degrees from the equator, That can well fit with the up to 15° inclination of these satellites. $\endgroup$
    – asdfex
    Aug 29 at 17:14
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note: This answer was written before being migrated from Astronomy, and the OP's response addresses the apparent motion. Upon further review of the video the OP feels that the previously described sudden change in motion didn't happen.

This is an interesting and well-written and reasoned question, but it may not be on-topic here in Astronomy SE unless someone can propose a 1/7 Hz astronomical object.

Certainly a tumbling satellite in MEO or GEO could potentially explain what you've described as long as the motion relative to the stars was consistent with zero or very slow and steady.

But you wrote:

The object was stationary for 2 minutes and then moved around quarter of a degree in 3 minutes.

and that makes an explanation based anything related to defunct satellites or astronomical phenomenon a real challenge.

So in this case if that sudden change in motion is 100% certain and beyond question, a very distant aircraft or weather balloon sound more plausible and we'll have to rule out artificial satellites.

Night vision goggles generally have image intensifiers, but they could conceivably be based either in intensifying visible light, or by imaging then intensifying near infrared or far/thermal infrared light. If you are looking at thermal IR then it wouldn't necessarily matter if the weather balloon (or aircraft) was currently in the Sun or not; it might be slowly rotating or rocking and exposing different temperature surfaces or doing something else.

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    $\begingroup$ Thank you for your answer. Since then I tried to be sure the object's movement, but I found out it was stationary all time during the video. Regarding this fact it will be a geosynchronous satellite. Only one question remains what is that blinking, those aren't rotating nor have blinking lights. I'm going to try to put the link to the video here (I don't know if it's allowed) youtube.com/watch?v=92Wak5fEITs $\endgroup$
    – Gergely Szucs
    Dec 16, 2021 at 11:34
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    $\begingroup$ There is one more object which is interesting. It's moving through the left side of the screen (at 1:52). According to the speed it is a low orbit satellite(s) but those aren’t travelling side by side. The Starlink is following each other in a line and never on the side. For a meteor the speed is low (there is one meteor at the end of the video). $\endgroup$
    – Gergely Szucs
    Dec 16, 2021 at 11:38
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    $\begingroup$ @GergelySzucs some geosynchronous satellites do indeed rotate. Some of them on purpose (like U.S. weather satellites launched before 1994 avl.class.noaa.gov/release/data_available/goes/index.htm ), and some by accident (a thruster or battery failure often imparts spin to the damaged vehicle). Even three-axis stabilized (non-spinning) need to rotate slightly from time to time to maintain the desired attitude, and many satellites have big flat panels covered in reflective foil that produce flashes when the sun is angled just right. $\endgroup$
    – Ryan C
    Dec 16, 2021 at 19:21
  • $\begingroup$ @GergelySzucs ... Geostationary satellites move against the background of stars (Celestial Sphere as seen from Earth's surface). They are only stationary when their position is measured in the Horizontal Coordinate System (Altitude and Azimuth). A telescope mounted on a tripod maintains a constant alltitude/asimuth direction, so a geostationary satellite would remain stationary in the telescope's field of view. The flashing object in your video moves against bot the star field and the field of view. $\endgroup$
    – Woody
    Aug 28 at 1:54
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    $\begingroup$ @GergelySzucs ... a geosynchronous satellite has the same period and orbital altitude as a geostationary satellite, but has a non-zero orbital inclination so its altitude (in the Horizontal Coordinate system) oscillates across the equator. This is a candidate orbit for the flashing object, but not a geostationary orbit. $\endgroup$
    – Woody
    Aug 28 at 2:01
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I too have observed the same thing. I am using ANVS 7 NVG goggles and can see a dim light strobing like an aircraft anti-collision light coming from deep space. I guarantee it's not an aircraft being I made a career working on aircraft. Every night I look towards the stars and can find it in the same general area. As mentions it does change position but very slowly. Super nova, pulsar, who knows. It is fun the watch along with the occasional satellite and meteor.

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    $\begingroup$ This is interesting, but more valuable as a comment. Since you are new to the Stackexchange network, it may be a while before you have the reputation required to post comments or in Chat. Unfortunately you will just have to ask and answer questions, and be patient until your reputation increases enough. $\endgroup$
    – Infinite_Maelstrom
    Aug 27 at 23:03
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My guess is that you may have been looking at a polar satellite. I am an airline pilot and I regularly astonish my colleagues when I jokingly predict that we 'shall see UFOs tonight', on return flights from Africa. And then, almost like clockwork, several UFOs do show up, around the time I predicted, approximately where I predicted. They light up brightly, seemingly in a stationary position, then disappear. In my case, as we are heading back from Africa to Europe, we are looking NNE (somewhere around 010 to 020 degrees). This occurs long before sunrise. As we are very much used to seeing satellites racing from west to east after sunset or before sunrise, when they are still basking in sunlight, these sightings are puzzling because they occur in the middle of the night. My guess, after many of these sightings, is that we are looking at high satellites on a polar orbit, where one facet of the satellite momentarily orients to a position to reflect sunlight from the far side of the earth. Their 'near stationary' position is then explained by the fact that on such a trajectory, at such a distance it will indeed move very little across the night sky. Their 'disappearance' is also sensible as, at such a distance, it doesn't take much of an angular change before the facet will no longer reflect sunlight in our direction. I am, however, surprised by the rapidity of the flashing of your sighting. This would have to be an object with a significant rotation rate to fit my guess.

Kind regards

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  • $\begingroup$ Why would a polar satellites emit a short blink like clockwork every six seconds? "...where one facet of the satellite momentarily orients to a position to reflect sunlight from the far side of the earth..." suggests your explanation is that rotating and creating periodic satellite flares and as you point out " This would have to be an object with a significant rotation rate to fit my guess." While I welcome to to Space Exploration Stack Exchange, "guesses" don't generally rise to the level of a good Stack Exchange answer. $\endgroup$
    – uhoh
    Jan 8 at 3:31
  • $\begingroup$ Perhaps you can do some searching for Earth observation satellites that rotate to do some kind of scanning? $\endgroup$
    – uhoh
    Jan 8 at 3:32
  • $\begingroup$ Of course you are entitled to your opinion about my answer. I thought it added a credible hypothesis which nobody, including yourself, had come up with yet. And, unless I am mistaken, nobody who answered has had similar observations, whereas I have seen hundreds, as described. As such, I thought that 'my guesses' were a worthwhile addition to this thread. $\endgroup$
    – Gert den Roeste
    Jan 8 at 16:48
  • $\begingroup$ If you have seen hundreds of objects that were "stationary for 2 minutes and then moved around quarter of a degree in 3 minutes" then they were artificial objects in the atmosphere (e.g. balloons, helicopters, drones/quadcopters), not satellites, and they would have been indistinguishable from stars until the started moving, unless of course they were blinking. The question author's description and recorded video is inconsistent with an object in orbit because of the steady-then-moving behavior shown in the video. So this is not an answer to the question as-asked. $\endgroup$
    – uhoh
    Jan 8 at 22:59

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