The good weather over the last few weeks extended to Saturday before last when we had a partial solar eclipse viewable in the UK. From Norwich, the eclipse was to begin at 10:10 UT and maximum coverage would be seen at 11:06 when the magnitude of the eclipse was predicted to be 0.413. The magnitude is a measure of the depth of the eclipse and is the fraction of the Sun's diameter that is occulted by the Moon. The eclipse was then predicted to end at 12.03 UT.
I was able to set up my Celestron NexStar 102 SLT on my HEQ-5 mount well in advance of the start of the eclipse. I intended to project the image from the telescope onto white paper using a 25mm eyepiece and a star diagonal. I used my Samsung Galaxy A21s phone camera to take images and the first image I took was at 10:16:52 UT:-
You can just start to see that the moon is creeping over the western side of the sun. Fortuitously the solar image is just about the right way up with north uppermost and west to the right (this resulted from using the combination of the star diagonal and the projecting the image onto paper). The prominent sunspot group on the left-hand side is AR4046 and to get an idea of what the sunspot activity looked like on this day here is the SDO image (taken at 19:54 UT, courtesy of NASA/SDO):-
After deleting poor images and duplicates, I had a total of 18 images from that morning but only until just after maximum eclipse. Rather than show all of these I have picked out six that are approximately 10 minutes apart and show the progression of the moon across the sun. The next image was taken at 10:25:36 UT:-
The chunk taken out of the Sun has increased noticeably but still appears to be increasing from the west. The next image was taken at 10:35:16:-
The same applies here. The moon is slowly encroaching over the sun. The fourth image was taken at 10:47:41:-
Now it appears that not only has the area of the sun that is occulted increased but also the moon appears to be moving northwards. The 5th image was taken at 10:54:42:-
The obscuration is approaching maximum and it is more noticeable that the moon has drifted northwards. The 6th and final image was taken at 11:06:25 and this is within 19 seconds of the eclipse maximum:-
From this image we can measure the percentage area of obscuration. Looking back at
my previous discussion of this, I have measured the chord AB to be 994 pixels and the diameter to be 1200 pixels. This gives that the angle
w is 1.952 radians (or about 112 degrees) and the observed obscuration is 33% (assuming that the sun and the moon have the same apparent diameter). From the predicted magnitude of 0.413 we can find the predicted obscuration and this is 30%. So pretty much in agreement given the potential errors.
All text and images © Duncan Hale-Sutton 2025 (except the SDO image).
