14 Aril 2012. Double Internationa Space Station (ISS) flyby over Sth Leics, UK skies. The first pass came over at 2112 hrs (left trail) and the 2nd pass came over at 2248hrs (right trail). To capture multiple ISS flybys in a single exposure like this can be done the following way:- Firstly check ISS flyby times using web sites such as http://www.heavens-above.com or a mobile app such as GoSatWatch. This will show not only times but directions of where the ISS appears and travels across the sky (for your location). For this shot the first ISS pass appeared on the SW horizon moving towards the East. The 2nd pass came from due West and headed towards the East (although disappeared overhead as it moved into Earths shadow). I set camera on a tripod pointing towards the SW sky ensuring the wide angle lens (Olympus 7-14mm) would capture both trails. I waited for the first ISS pass and as it came into view shot 15s exposures (F4, ISO 500) continuous for 5 mins (approx 20 shots). I then switched the camera off, left it and waited for the 2nd pass (approx 1.5 hrs later). After returning for the second pass I kept the camera in exactly the same position and commenced firing the same 15s exposures. Because the 2nd flyby disappeared overhead (instead of flying from one horizon to the other) I only needed to shoot approx 10 exposures. The foreground lighting you see with my shadow was done during the first pass. I fired off a remote flash a couple of times as the camera was shooting. Once complete I took camera back indoors & downloaded all the images. Using stacking software (StarStax) I then imported all images from both 1st & 2nd passes. The software then automates and produces a final composite image. This final composite shows the multiple passes in one single exposure...Simples :-) PS I have used this method for 3 and 4 No ISS flybys, when we are luck enough to get that many :-) Happy iSS hunting.
ISSstarsastronomynight skyOlympusE5Mark Humpage