ISS Transits

With the advent of easy to use prediction software such as Calsky and Thomas Fly's ISS Transit Alert Service it is now possible to plan is advance to video both Solar and Lunar transits by the ISS. While this is simpler in some respects than tracking the ISS in real time (since you know where to point the telescope in advance) is does require that you have a fast video camera (most transits are 0.5 seconds or so i.e. about 12 video frames total) and that your whole setup is mobile. A typical transit path will only be a couple of miles wide on the surface of the Earth.


Because the ISS is barely visible on the captured video I have presented the results here as a hand drawn dot in the position from each frame as I can best judge it. The background was obtained from the stack of 13 frames processed in Registax2 (compare with the raw frame on the right!). 
You can also download a DivX5 video of the transit here (690kB). Note: this is slowed down by a factor of about 5 compared to real time.
Lunar transit   11th November 2003   02:22:12 UTC
GPS Position:  WGS84  53:17:53N  2:35:42W
ISS:  In shadow,  Range 441km (274 miles) 

Success - just!  This transit was only 2 miles from my home so I felt I had to give it a go despite cloudy conditions all evening. At about 01:45 I set out for my chosen spot only to find it shrouded in mist. A quick change of location to a nearby country lane and another few minutes to get the ETX-70 and camera set up. 

There was a lot of fast moving cloud and some general haze around but the lunar disc was visible. The ISS was in the Earth's shadow so would only be visible during the transit. However, I did not see this on the camera screen at the time as the telescope was right on the limit of being able to resolve the ISS but close examination of the captured video showed the station transit about 1.5 seconds before the predicted time.

None of the frames really show any detail although there is a hint of a T-shape in one (circled below). Shutter speed on the Canon MV-650 was 1/1000th. The ISS is visible in 13 frames i.e. 0.5 seconds transit time.

This transit also provided confirmation of the accuracy of the  ISS Simulator which shows an almost perfect match with the observed transit. 
Download a simulator config file for this transit here

Click here for prediction details used prior to the pass

sun_030626.jpg (12931 bytes) Attempted Solar transit 26th June 2003
Tried to capture an ISS solar transit but clouds intervened at the critical moment. Had to settle for this full disk image - a stack of approx 400 frames captured from digital video.
MV650i on 40mm Meade Plossel eyepiece.

Related Web links

John Locker - LX90 images including 2 solar transtis on consecutive passes

Ed Morana - fantastic detail from an LX200 GPS


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Page content 2001-2007 Mike Tyrrell