Partial solar eclipse of 2022 October 25

Greetings everyone, I am looking for a few amateur colleagues who can collaborate in observing the phenomenon. More precisely, to establish the timing of the contacts and the maximum phase, together with the contact angle (clockwise from the north). For arrangements cross19@libero.it.
Thank you and greetings to all.
Giovanni (Italy)

Been a nice sunny morning here in Leicester. Observed the eclipse with the students from Leicester University Astro-soc who had organised the event. Made some drawings with my 40mm PST including one showing the lunar limb close to a sunspot.

Dear friends, I present to you my photographs of today’s solar eclipse. I have just one question for you: How much would you have bet that the cloud would not move for the duration of the phenomenon? Is this a statistically significant phenomenon? It went wrong for me, very wrong. Best regards to you all.

Hi Duncan,

The dynamics of solar eclipses are very well known, although that’s no reason why you shouldn’t measure the obscuration for yourself.

The Observers’ Challenge and the BAA Handbook listed the obscuration percentages for various locations, whereas the article in the October Journal gave the magnitude values (fraction of diameter obscured by the Moon). Some casual observers were put off by the small obscuration percentages, not realising that the magnitude values signified impressive partial phases. I prefer that ‘eclipse magnitudes’ are quoted in eclipse work.

Some teams observe total solar eclipses to measure the Sun’s radius, aiming to determine any evidence of long-term change in its diameter, e.g.

‘Estimating the Eclipse Solar Radius from Flash Spectrum Videos’ in

https://www.iota-es.de/JOA/joa2022_2.pdf

(17 MB download)

Cheers,

Alex.

Hi Nick,

And here’s another animation I constructed showing that, although it appears to “roll” in an arc across the Sun in the previous animation, the Moon’s track across the Sun is indeed a straight line. Made by not removing previous frames when adding a new one until the straight line position is reached, and then successively removing early frames until last contact.

Hi Duncan,

Happy to hear you liked my video animations. Given the “rather variable” (!) conditions I experienced during the eclipse; the need to take several shots on different exposures each time to combat the variable cloud cover, as well as experimenting with two different density filters for the same reason, and the problem of taking shots at the required 5 minute interval if clouds decided to intrude meant that the individual frames needed A LOT of processing to get them consistent enough to be assembled into the animations. I’m thus glad to know that my efforts have been appreciated! The second one is particularly intriguing, as you say – I haven’t seen anything similar on the Internet so I was rather pleased it came out so well.

I also found equations of the form you derived on the Internet but wanted to explicitly avoid that approach so I could get my results via an entirely different route and thus be confident in the comparison between the two methods. Doing it “the hard way” also enabled me to sort of work backwards from the answer and derive an again multi-step process for converting from magnitude to obscuration, which I’m sure will prove useful.

In terms of the measurement and calculation errors which might be expected, the fact that I was able to use a much larger image gave me advantages in both precision and accuracy. More precise as I was working at the 1 in 1000 level whereas you were at 1 in 250, and potentially more accurate as, because of the greater precision, I could determine my measurements at a smaller “step length”. That is, in my case a 1 pixel step hardly moved the “marquee” lines I was using to measure distances, and so the lines could be more closely aligned with the Sun, whereas your 1 pixel change will have moved the measurement point by four times as much so you might not have been able to line things up exactly. I still had the problem of estimating the correct points to measure from of course, given that my image was not sharp (because of the limitations of the home-made filters I was using), but even so I believe that my distances were probably correct to +/- 1 pixel. Translated to the difference this would make to the final result, as compared to the nominal 1200 by 846 figures, the maximum difference (in the cases 1201 / 845 and 1199 / 847) was just less than 0.5% which is still pretty acceptable.

The same website I used to determine the theoretical magnitude and obscuration also gave the ratio of the diameters at my maximum eclipse, which was 0.99253. The assumption of equal sizes is thus highly reasonable, involving potential errors of only the same order of magnitude as those involved in taking the measurements and probably less as the radii are used as part of more complex equations rather than as direct parameters. The SD values on the NASA chart are of course those relating to the point of absolute greatest magnitude (over eastern Siberia) so, while indicative of the situation, will not be applicable to the UK as the Moon will have moved along its orbit during the eclipse.

Steve