Transit of Mercury

By Richard Harvey

The transit of Mercury which occurred on the 11th November 2019, was the third Mercury transit this century, (other transits being 2006 and 2016). The next transit however, won’t occur till, 2032, so we felt it important that a group observation session should be arranged for the 2019 event.

With the Sun being only twenty degrees above the horizon at first contact, and heading lower, it was vital that we found an observation spot that offered a clear view of a low horizon towards the south. The Vineyard at Halfpenny Green seemed an ideal location, and we were lucky to be given permission to use the area outside the café.

Members started arriving around 11.30, to allow plenty of time for setting up scopes in readiness for first contact at 12.30. A fine array of telescopes adorned the grass area, with refractors, reflectors, and Schmitt-Cassegrains. Baader filters were firmly secured, and photographic equipment poised in readiness.

Telescopes set up for transit of Mercury
Telescopes set up with solar filters ready for the transit of Mercury
Members set up ready for the transit
Members with their scopes set up ready for the transit

Unfortunately, cloud rolled over just before 12.30 and we missed first contact. In fact, for the first 45 minutes of the transit we weren’t given much chance to observe the event due to cloud. Eventually however, the cloud did disperse, and we were able to easily see the tiny planet in silhouette against the solar disc. Many of us had observed the transit of 2016, so knew what to expect. The size of the planet (a mere “pin prick” someone said), could be seen as underwhelming, but given that it’s quite rare to even see Mercury, it’s always a thrill to spot at the fleet-footed alien world. (in the recent years I’ve only seen Mercury three times. The two recent Solar transits, and a daytime sighting in Turkey in 2006 during a solar eclipse).

One of the most popular pieces of viewing aids on this afternoon was Linda’s Sunspotter. This attractive and intriguing looking wooden optical aid is designed specifically for viewing the Sun. Linda and I first saw one of these in Kentucky in 2017, when we were over for the solar eclipse. Using the Sunspotter, the image of the sun is safely projected on a white background, and the planet could clearly be seen.

Linda's Sunspotter telescope
Linda’s Sunspotter telescope, projecting the transit onto a screen
Graham Dale's photo of the transit
Graham Dale’s photo of the transit

Graham Dale used a Sky-watcher Esprit 100 ed super APO to get some beautifully clear photographs of the transit.

The sun set with the planet still in transit, and a few of us enjoyed some hot food and drink from the cafe’s impressive menu, and some members took the opportunity to do some early Christmas shopping in the Vineyard’s craft shops and delicatessen.

Doug giving members an update at the talk that evening
Doug giving members an update at the talk that evening

Later that evening, at our Highfields meeting, we were able to see some of the images taken by members on the big screen, and Trevor and Steve Clifton kindly bought in copies of their very successful imaging session to share with other members. At the next Perton Library Astronomy Group meeting, Doug gave a presentation on the event, which we all agreed had been a resounding success. Our thanks to the staff and management of Halfpenny Green Vineyard.