A Busy Day Under the Sun - Saturday 22 August 2026

Saturday 22 August turned out to be one of our busier solar observing sessions of the summer, with a steady stream of visitors keeping the whole team on their toes. From 10:00am to 3:40pm, around 400 people came up to the Royal Observatory Greenwich to take a safe look at our nearest star. There were a few patches of cloud throughout the day, but the Sun cooperated often enough to give everyone a fine view, right up until the cloud turned persistent in the afternoon and brought the session to a natural close.

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There was plenty of kit on show. We had three hydrogen alpha telescopes set up, each revealing the Sun's fiery edge with prominences reaching off the limb, along with a smart telescope to capture the view digitally. Pride of place, though, went to Tim's Calcium-K telescope, which lets us observe the Sun in the light of ionised calcium, known as the calcium K line, or CaK for short. Where the hydrogen alpha scopes pick out prominences and filaments, the CaK view brings out the bright, mottled regions of the Sun's lower atmosphere, giving visitors a completely different way of seeing the same star.

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The real talking point of the day was a single sunspot sitting on the solar disc. It may have been just the one, but it did not disappoint. Visitors were particularly taken with the Sunspotter, which projects a bright, safe image of the Sun and made the sunspot easy for everyone to see. It proved a wonderful way to explain what sunspots actually are, how big they can be, and why they come and go. There is something about seeing a genuine feature on the Sun projected right there in front of you that captures people's imagination, and this one certainly did.

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Two solar images taken at the event. H-alpha by Alec Knox, and Calcium-K by Tim Rickard.

We were also delighted to be joined by friends from the Norman Lockyer Observatory, who came along to visit. It was lovely to have them with us, and they were especially keen to talk about our CaK setup, swapping notes and comparing experiences of observing the Sun at that wavelength. Sharing that kind of enthusiasm with fellow astronomers is one of the real joys of these sessions.

The Flamsteed solar volunteers, along with those assisting our guests from the Norman Lockyer Observatory.

After a busy few hours of sharing the Sun with around 400 visitors, and enjoying the company of our guests from the Norman Lockyer Observatory, it was time to pack the equipment away as the cloud settled in for good. A sunspot that captivated the crowds, several different ways of viewing our star, and good company to go with it. A thoroughly rewarding day all round.