Occultation by Triton

On 5th October 2017 it was predicted that Triton, a satellite of Neptune, would pass in front of a 12th magnitude star as seen from a swathe of the Earth which included the UK.  This is a very rare event and one difficult to observe.  However the combined brightness of the two objects was predicted to fall 1.4 magnitudes, which is a factor of about six, so, if I could resolve the pair from Neptune, I thought I might be able to observe it.
On the right is an animation created from 48 individual pictures taken at 33 second intervals across the time predicted for the occultation. The brighter object is Neptune, the fainter one is an unresolved image of Triton and the star.  The animation runs for about 6 seconds, pauses for 5 seconds and repeats.  The occultation can be seen about half way through the animation.  I measured the brightness (in arbitrary units) of the fainter object in each image and plotted this against the time of the picture.  This is presented in the second picture.
From the data in the graph I was able to measure the time of the centre of the occultation as 23:49:14 UT and the length of the occultation as 132 seconds.  These figures correspond quite well with the predicted values.
At the time Neptune was 4,400 million kilometres away so the accuracy of the known positions of Earth, Triton, and the star must be amazing for such a prediction to be made.

A more detailed discussion of this event is on my web site.