Sorry Rodd,
What was I thinking?
You can work out the brightness from your image. It seems they were about the same mag as the 5th star in Crux at their brightest. This would make them difficult to see.
Also the broken trail threw me untill I realised it was a stacked image.
This could be used like a rotating shutter.
From this you may be able to work out the approx. period and thus the approx. altitude. This and the direction may lead to an identification.