I'm not sure what this is....

For everyone that follows my post, they will know that I have been messing with my star tracker and taking advantage of the few clear nights we've had over that past couple of months.
A couple of nights ago, I again, decided to shoot Orion, but the full constellation instead of just concentrating on the great nebula, sadly, cloud started to come in, so I called it a night after about 50 mins or so, however, in that time, I managed to shoot 45 shots.

Camera settings:
55mm
ISO 640
60 Second Exposures
Tracked using iOptron tracker.

When processing the images, I decided to see what they looked like as a timelapse, this is when I saw the light in the sky, basically on the above shot it just looks like any old meteorite, however, this is over 18 shots, so if my maths is correct, it took 18 minutes to travel that over the shot, which is way way too slow for a meteorite, satellite or even a plane, so I'm not sure as to what this could be.

Here is another shot cropped in for a closer look, bear in mind this is all the shots put together to come out with this continuous line.

The above shot is what it looks like on a single image, as you can see, it doesn't travel far at all for a one minute exposure.

So Hive friends, do you have any ideas as to what it could be?

Here is a film of what it looks like in motion, as I meantioned before there are only 45 shots in total and 18 that contain the light, each shot is at 60 seconds.

Enjoy....