This is the third post of Suzanne’s mission to Sweden for the Transit of Venus. The second post is here.
What do you need for a short trip to Sweden? Thermals (I’m told it’s unseasonably cold out there at the moment), passport … and of course, a telescope and a plastic funnel.
The FLODA31 team have not been idle in the run up to our arrival: they have teamed up with the local architecture school to build a dedicated viewing platform. This is what the design looks like:
The two cirles are inspired by the orbits of Venus and the Earth, highlighting (and somewhat exagerating, of course) the difference in their orbital inclinations which makes the transits of Venus as seen from the Earth such rare events. The Sun will rise at one end of the elongated window, and will gradually edge across it as the transit unfolds. The window will be made of welders #14 glass, so onlookers can watch the spectacle safely.
Abby and Chris from super/collider, who are organising the trip, got there last week and got stuck in too, and as of yesterday (June 2), the Earth’s orbit was almost complete:
Most of the people coming from the UK will arrive at Umea on Monday afternoon. After a brief visit to Umevatoriet Observatory, who are also involved in preparations for the transit viewing, we’ll drive the final two hours to the tiny hamlet of Floda.
I am really looking forward to seeing the purpose-built viewing platform for myself, I think it will frame the transit in a spectacular way. But Venus will still appear quite tiny on the solar disk – at the limit of what can be discerned by eye – so it will also be good to have a magnified view. Chris will have a pair of binoculars on a tripod, as well as a small telescope, both of which he will equip for Sun-watching by covering their entrance apertures with solar viewing film.
To complement this, I decided to build a sun funnel, which attaches to the eyepiece of a small telescope, allowing several people to enjoy the view at once, as in the example below:
By the beginning of last week, I had all the ingredients:
… though the funnel had to come all the way from the US: apparently no-one sells black funnels of this particular shape in the UK. The company that sells them in the US wouldn’t deliver abroad… but luckily my colleague Fraser Clarke happened to have an observing run at Palomar Observatory in early May, so I got it delivered there and he kindly brought it back for me. Sourcing the rear-projection fabric was a bit epic too. I only needed a foot square, but the minimum amount I could order was 3 x 1.2m… so when I get back I’ll have to figure out what to do with the leftovers. Suggestions welcome!
Figuring out what telescope to use was a little epic too. Refracting telescopes are preferrable because of the amount of light a reflecing telescope would focus onto the eyepiece when trained on the Sun. Also, you really want a motorized mount: tracking the Sun manually for several hours could get tedious. The Oxford Physics teaching course had a nice Meade ETX-125 they were willing to lend me. However, the case for it was too big to take on the plane as hand luggage, and it is rather too fragile to go in the hold. So I thought I would buy a smaller, portable but still motorised telescope, such as the ETX-70 Backpack – this would be quite a nice thing to have when going camping anyway. But I was warned the fixings which hold the optics in place are made of plastic, so there would be a high risk of melting them when pointing the telescope at the Sun… no go.
Fraser came to the rescue and suggested I use the star-finder of the Philip Wetton telescope – the 11″ telescope we normally use for undergraduate projects in Oxford.
We tried it, and it works really nicely, giving a lovely view of a couple of active regions. It also fits into a smaller case that I should be allowed to take as hand luggage. Only one small hitch: it has no mount of its own, and we couldn’t find a spare motorized mount.
At this stage, I asked Abby if she knew anyone who could help locally – and finally I think we have a solution. Bastien from Umevatoriet Observatory very kindly spent a few hours equipping an equatorial mount they had lying around with a motorized drive. Now we only have to hope that we can attach the finder scope to it… I’ll find out tomorrow.
The weather forecast for the next few days is not perfect, but it is a lot better in Northern Sweden than in the UK, so I’m quietly optimistic.