Frequency of Umbral Flashes
Taken by David Wilson on August 12, 2026 @
Inverness, Scotland
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Details:
For some reason, my little DIY solar scope is good at catching umbral flashes. So I made an app to measure the flash frequency and speed of surface waves. It works by measuring brightness of a sample area over time. The video shows my first attempt with a cross section of AR4528 on the 12th and 13th of August but it is hard to discern the surface waves. Starting again, I discovered the best way is to have a 2pixel square sample area just at the edge of the central dark umbra and plot brightness over time. The next 2 images show this approach for the 12th and 13th with very clear brightness peaks. The last image shows how I calculated the frequency of each. Note how on the 13th at 3500secs, the frequency increases and then slows right down. Next step is to calculate surface wave speed. Big thanks to the Powershotters camera forum for prompting this app.
Photographer's website:
https://tinyurl.com/5d83mn5j
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