Strange blinking light in StarLapse

[ThomasH]

Hi

I made a timelapse in 2013 and noticed a strange blinking light in the bottom left corner in the end. I think it's a satellite, but the speed confuses me, since it took 15 minutes to travel this distance.
Also I finde the blinking strange.

Shot in Denmark August 13 2013, the "UFO" was there fra from 00:38 to 00:53,
Shot at 10 mm (1,6 crop) on a Canon EOS 7D, shutter 25 s, probably pointing northwest (EDIT: south west)

(I used 37 frames and 750 simulation speed in Sitrec)

approx.: 55.728641154649154, 12.35538545712806

Can a satellite move this slowly?
Is it too long ago to identify it?

-- EDIT we solved this --
I can't get Sitrec to work properly, vFOV should be 73,7 degree on a 16mm lens and I can see on my TimeLapse, that the north star is over the picture in the right side and I can't see the ground.
If I make vFOV 73.7 in sitrec I can see both the ground and the north star - I can't identify any other stars (but I'm really bad at this)
---


Video and a star trail photo.
https://www.jottacloud.com/s/1363851d766424b4a599c8a197830171d81

Please help me
Thomas.

EDIT: it moved only 13° in 16 minutes. And if the blinking is from a rotation, it rotates every 106 seconds.

 

[Mick West]

How sure are you about the exact date and time. [Edit: it seems pretty good with the match below]

I can't identify any other stars (but I'm really bad at this)

It's surprisingly difficult - especially if the time and zoom are a bit off. I usually have to resort to using https://nova.astrometry.net/ But that was no help this time.

But I did find a bit of match:
https://www.metabunk.org/sitrec/?cu...azonaws.com/1/2013 ThomasH/20250811_161437.js

It's hard to match the other stars on the right, this is partly current limitation of Sitrec, which I need to work on.

Is the image cropped?

Is the lens rectilinear?

 

[ThomasH]

How sure are you about the exact date and time. [Edit: it seems pretty good with the match below]


It's surprisingly difficult - especially if the time and zoom are a bit off. I usually have to resort to using https://nova.astrometry.net/ But that was no help this time.

But I did find a bit of match:
https://www.metabunk.org/sitrec/?custom=https://sitrec.s3.us-west-2.amazonaws.com/1/2013 ThomasH/20250811_161437.js

View attachment 83011

It's hard to match the other stars on the right, this is partly current limitation of Sitrec, which I need to work on.

Is the image cropped?

Is the lens rectilinear?

Date is 100%, I rarely use it anymore, but last year I found out my 7D was 12 minutes wrong, but I don't think it was in 2013.

Oh you're right, I didn't looked so much south since I was sure it was north!

No I just made that video from the raw photos, distortion corrected in Camera RAW.
It's a Sigma 10-20mm in 10mm,

...so the FOV problem I had, was because I was looking north - DOH!!!!

But in generel, can a satellite look like that and travel so slowly ?

 

[JMartJr]

But in generel, can a satellite look like that and travel so slowly ?

I'd think a satellite could cross the sky at most any pace slower than the usual one we see of satellites in LEO, as higher orbits are slower (and have more distance to cover!) So the speed would not seem impossible.

I have no idea how visible satellites at higher, slower orbits are, however. I guess it would depend on how big and shiny they are?

Blinking would seem to indicate tumbling, I wonder if it is a spent rocket booster?

 

[ThomasH]

....btw Mick, I could really really use a feature to set the aspect ration on the right window, it would make it so much easier to match.

 

[ThomasH]

I'd think a satellite could cross the sky at most any pace slower than the usual one we see of satellites in LEO, as higher orbits are slower (and have more distance to cover!) So the speed would not seem impossible.

I have no idea how visible satellites at higher, slower orbits are, however. I guess it would depend on how big and shiny they are?

Blinking would seem to indicate tumbling, I wonder if it is a spent rocket booster?

I don't know, but I hope some of the clever types in here did
But hey, if no one can, it actually IS A UFO!!

 

[ThomasH]

How sure are you about the exact date and time. [Edit: it seems pretty good with the match below]


It's surprisingly difficult - especially if the time and zoom are a bit off. I usually have to resort to using https://nova.astrometry.net/ But that was no help this time.

But I did find a bit of match:
https://www.metabunk.org/sitrec/?custom=https://sitrec.s3.us-west-2.amazonaws.com/1/2013 ThomasH/20250811_161437.js

View attachment 83011

It's hard to match the other stars on the right, this is partly current limitation of Sitrec, which I need to work on.

Is the image cropped?

Is the lens rectilinear?

vFOV 63 and 229 degrees and tilt 74.8 seems to fit.
Is the FOV wrong in Sitrec?

 

[Mick West]

vFOV 63 and 229 degrees and tilt 74.8 seems to fit.
Is the FOV wrong in Sitrec?

I did a rough (handheld) test with my 7D and a 10-22mm (at 10mm), and my 120" wall fills the frame at about 88" away, which gives vertical FOV of about 68°, which seems consistent with your 63°

 

[Mick West]

Is the FOV wrong in Sitrec?

I don't think so. I've measured it on things like a large sphere in the distance.

No I just made that video from the raw photos, distortion corrected in Camera RAW.
It's a Sigma 10-20mm in 10mm,

Has that distortion correction cropped it at all?

 

[ThomasH]

I did a rough (handheld) test with my 7D and a 10-22mm (at 10mm), and my 120" wall fills the frame at about 88" away, which gives vertical FOV of about 68°, which seems consistent with your 63°

All online FOV calculators say 73.74 degree on 16mm full frame ..and the same in 10mm and a crop sensor

 

[ThomasH]

I don't think so. I've measured it on things like a large sphere in the distance.


Has that distortion correction cropped it at all?

Hmm yes the correction actually takes a bit of the corners, I will check it out. 5 min.

EDIT: Only the corners, the middle vFOV is exactly the same.

 

[Mick West]

All online FOV calculators say 73.74 degree on 16mm full frame ..and the same in 10mm and a crop sensor

Yeah, but that's not what I get in practice. I'm seeing about 5° less

Hmm yes the correction actually takes a bit of the corners, I will check it out. 5 min.

I can see why it would. Look that the top edge here, the crown molding is curved. To straighten it you'd need to push out the corners.

My 68° vFOV measurement is for the middle vertical span of this image. It would be more at the sides.

 

[ThomasH]

Yeah, but that's not what I get in practice. I'm seeing about 5° less
View attachment 83017

I can see why it would. Look that the top edge here, the crown molding is curved. To straighten it you'd need to push out the corners.

My 68° vFOV measurement is for the middle vertical span of this image. It would be more at the sides.

Oh I edited my answer, it doesn't change the vFOV.

 

[Mick West]

Oh I edited my answer, it doesn't change the vFOV.

Do you still have the lens and camera? Can you try measuring it? (use something as far away as possible, focus changes FOV)

 

[ThomasH]

Yes but how do I measure the angle?

 

[Mick West]

focus changes FOV

Although maybe not much with a wide angle lens. I was thinking of a P900 telephoto where the horizontal FOV varies from 1.3° to 1°, based on focus.
https://www.metabunk.org/threads/ho...ere-with-binoculars-sunspots.8646/post-205386

Yes but how do I measure the angle?

Photograph something that perfectly fills the vertical FOV, like the wall in my photo. Measure the height of the wall (h) and the distance to it (d)

Then vFOV = 2*atan((d/2)/h)

Use cm, m, or inches, no difference.

You can check your math with ChatGPT:
https://chatgpt.com/share/689a2cd8-92fc-8003-853b-9c7e47078071

 

[ThomasH]

Do you still have the lens and camera? Can you try measuring it? (use something as far away as possible, focus changes FOV)

...are you sure it's not something with 3:2 vs 16:9 in the window that distorts the numbers?
I think an aspect ratio option would make super much sense.

 

[ThomasH]

Although maybe not much with a wide angle lens. I was thinking of a P900 telephoto where the horizontal FOV varies from 1.3° to 1°, based on focus.
https://www.metabunk.org/threads/ho...ere-with-binoculars-sunspots.8646/post-205386
View attachment 83018



Photograph something that perfectly fills the vertical FOV, like the wall in my photo. Measure the height of the wall (h) and the distance to it (d)

Then vFOV = 2*atan((d/2)/h)

Use cm, m, or inches, no difference.

You can check your math with ChatGPT:
https://chatgpt.com/share/689a2cd8-92fc-8003-853b-9c7e47078071
View attachment 83019

You're right (I hate you always are)
68.6° was my result
That back calculates it to 11mm.

Anyway!! An aspect ratio in the window would be great.

And what the heck is that blinking thing? There are no known satellites there and not so slow

 

[ThomasH]

https://www.metabunk.org/sitrec/?custom=https://sitrec.s3.us-west-2.amazonaws.com/17922/2013 blink/20250811_182858.js

This is the closest I get - still a bit strange it's like it's shifted horizontal and your window is stretched a bit.
But no satellites and no one goes SO slow.
Can it be some kind of space debris ?

 

[Mick West]

There are no known satellites there and not so slow

Sitrec only pulls in LEO satellites - i.e. ones that move significantly. This is to limit the size of the query, I use:
/MEAN_MOTION/>11.25/ECCENTRICITY/<0.25/

So the "ALL" in the menu is a bit misleading. You could get your own TLE and drop that in.

 

[ThomasH]

Sitrec only pulls in LEO satellites - i.e. ones that move significantly. This is to limit the size of the query, I use:
/MEAN_MOTION/>11.25/ECCENTRICITY/<0.25/

So the "ALL" in the menu is a bit misleading. You could get your own TLE and drop that in.

If I knew what TLE was maybe I could

 

[jarlrmai]

If I knew what TLE was maybe I could

https://en.wikipedia.org/wiki/Two-line_element_set

A two-line element set (TLE, or more rarely 2LE) or three-line element set (3LE) is a data format encoding a list of orbital elements of an Earth-orbiting object for a given point in time, the epoch.

 

[ThomasH]

https://en.wikipedia.org/wiki/Two-line_element_set

A two-line element set (TLE, or more rarely 2LE) or three-line element set (3LE) is a data format encoding a list of orbital elements of an Earth-orbiting object for a given point in time, the epoch.

It's beyond my understanding
...but until now, I've caught a UFO

 

[ThomasH]

ChatGPT helped me. It could be a tumbling rocket.
Request send to CelesTrak