Under the Hot Sun – Solar Viewing at the ROG, Friday 15 August 2025

The mid-August solar viewing session at the Royal Observatory Greenwich took place on one of the hottest days of the year. By 10.15am, we were set up at the Dolphin Sundial and ready for action, with clear skies overhead and early interest from visitors.

Although the sunspots were on the small side, the prominences and filaments more than made up for it, with striking structures visible in both H-alpha instruments. Clive’s decision to bring along a second H-alpha telescope proved invaluable, easing the pressure on the main scope and helping us keep the queues moving smoothly.

The heat quickly became the defining feature of the day. Temperatures reached nearly 30°C in the shade – and far higher in direct sunlight – making breaks and rotations essential. The volunteers coped superbly, keeping visitors engaged and the session running seamlessly.

The day also had a different rhythm from usual. With the site noticeably quieter than normal, we alternated between lulls, where there was no queue at all, and sudden bursts of activity when families arrived in groups. By the time we packed up just after 3.30pm, we’d welcomed around 350 visitors. Fewer than some sessions this summer, but still a healthy total given the conditions.

A huge thank you to our volunteer team – Sara, Mike D, Simon, Clive, Yvonne, Alec, Paul, Katie, Mike M, Giorgio, Tim, Leslie, and Richard – for their energy, patience and good humour throughout a very hot day.

Our next public solar viewing session is scheduled for the weekend of 23 or 24 August. After a day spent under the hot Sun, we’re looking forward to the final two weekends of the season – hopefully with more clear skies and fewer degrees on the thermometer!

Pictures from the event (by Simon Hurst, Alec Knox and Mike Meynell):