Partial Solar Eclipse 25th October 2022

We had a partial eclipse of the sun on Tuesday 25th October. From our location near Norwich first contact with the moon was to begin at 10:07, maximum coverage was to occur at 11:00 and last contact at 11:55 (all times BST). I had a flu jab appointment at 11am and so I didn't have much time to set anything up. In the end I decided to use my 8x24 binoculars to project the image (twice!) onto a sheet of white paper. The first image I took was at 10:39 and the last at 10:47. The best of them was this image at 10:45 (15 mins before maximum):-

I quite like the fact that this looks like two eyes looking down. Looking at this image I think that the "bite" taken out of the sun is much less than 25% of the total area of the disk. To see this imagine dividing the sun into four equal quarters of cake. The bite can be seen to roughly sit in one of those quarters but it by no means covers the whole quarter. However, I do reckon that the bite covers more than half of that 25% (i.e. more than 12.5%). So perhaps 15 or 16%. I must try and calculate it. London was predicted to be 15.2% at max.

I have now (18th November 2022) done some work on calculating the obscuration (the percentage area of the sun that is covered by the moon as it is called). Have a look at this diagram below:-

The shaded area represents the area of the sun that is eclipsed by the moon. I have assumed that the moon and the sun appear to be the same angular diameter on the sky. I have found that the percentage obscuration is given by 100 (w - sin w) / pi where the angle w is in radians. To find w you need two measurements; the length of the chord PP' (which we can call l) and the diameter of the sun (which we call d). Then w = 2 arcsin (l/d). 

In the above picture of the eclipse I chose the left-hand projected image which was more well defined and circular and measured l to be 209 pixels and d to be 311 pixels. This gave the obscuration to be 15.2%. But I think this is a coincidence that it is close to the London value!

All text and images © Duncan Hale-Sutton 2022