The images show two areas of unusual refraction moving across the Sun during the transit of Mercury on the 7th May 2003. The images are from a PAL VHS movie and are spaced 1 or24 frames apart except for a gap of about 7 seconds around image 31 between the two events . More detailed timings can be seen from the UTC clock that is recorded on the images. The image quality of Mercury early in the transit was good but started 'boiling' badly in the few seconds before the first event. The boiling continued until a second or two after the second cell edge went through when it improved and remained good for the rest of the transit. I thought at the time that the deterioration of the seeing may mean that we would not be able to image the rest of the transit.
The refraction may be related to aircraft con trails or may be the result of large scale atmospheric cells as the land surface heated up though this is unlikely as the seeing improved even though the heating continued. The last 5 cloud images show the effects on an aircraft con trail about an hour after the effect was imaged on the Sun. Note that in one frame the distortion is so bad that Mercury disappears and also the distance that the bright area is visible from the Sun. No more events were noticed during the transit.
It is interesting to note that Mercury had an apparent diameter of 12 arc seconds and disappeared completely for two frames ( Numbers 19 & 20 ) and three frames Numbers ( 64, 65 & 66 ) in the second event. Atmospheric events of this type and magnitude can have a significant effect on asteroid occultations or monitoring short term variable star events.
Images were taken from the Croydon Astronomical Socities Observatory at Kenley Surrey UK
Here is a .GIF animation of this event ( beware it's 12 MBytes ! ) I also have a movie of this event but it is too large to put on this web site
Click on any picture to see a
larger view - you really need to start with frame 1 and view them in sequence to
make sense of the event.
About 1 hour later - distorted Aircraft Con Trails
Updated 9th January 2006 20:17 UTC