I Help identifying this Tumbling object in a night sky photo from Namibia

[Devin-M]

This is a crop from which I roughly calculate the amplitude of the curved line to be 15 arc s using the Astrometry.net data below. This shouldn't be a problem with Autoguiding.


View attachment 334791

Based on the last photo, If you want to assume it’s orbital & 350 miles (563.2km) away, 15 arc seconds gives a size of 134 ft (40.8m). If it’s traveling 8000 m/s at orbital velocity that’s 196 body lengths per second or 2940 arc seconds per second. The path width is about 8px giving about 1.8arc sec per pixel (assuming path width 15 arc sec). The path length is 336 px giving a 604.8 arc sec path length. This implies a path time of 0.205 seconds. I count 19 potential rotations in that time giving 92 rotations per second or 5520rpm, rotating faster than a car engine at freeway speeds. This seems implausible as a 40m long rocket body would likely not be able to tumble 92 rotations per second without rapid disassembly. Since the stars are round we can rule out telescope wobbling for part of the exposure. For me, this leaves firefly flapping its wings as most plausible explanation.

 

[Devin-M]

0.796 arcsec/pixel

Ps after you uploaded it here, the image size was scaled down to 1.9 arc seconds per pixel.

Pixel scale:

1.9 arcsec/pixel

 

[timmdeeg]

Since the stars are round we can rule out telescope wobbling for part of the exposure. For me, this leaves firefly flapping its wings as most plausible explanation.

I don't have this experience myself but guess that autoguiding would keep the stars round.

Other opinions?

 

[timmdeeg]

This issue will be most probably be discussed in the magazine "Sterne und Weltraum". I'll keep you informed.

Here comes Ulrich Bastian's comment, he is one of the founding fathers of Gaia:

My translation:

It seems most probably the trace of a satellite. It begins in the middle of the image and from there sloping to the bottom. It is parallel to the second satellite trace, not shown here. The wobble motion is for sure not due to the motion of a sky object but caused by a fast vibration of the optical instrument or the mount:
Assuming the usual angular velocity of a satellite the wobble period would be around 0.01seconds. The full amplitude is around 8 to 10 arc sec corresponding to 13 - 16 meters assuming a distance of 300 km of the object. Probably the vibration was cause by touching the instrument ... . It was already decayed when the second satellite went through the picture. At its end its amplitude is recognizably decreasing already.

I would like to add guiding was good enough to keep the stars almost round.

 

[chemisttree]

The stars might be round because they are significantly dimmer than the satellite. Their round appearance was an image built up from an extended exposure for which the vibration contributed very little.