What a day: the last of the second heatwave of the UK year (so far) with temperature records having been broken multiple times and the whole thing made far worse by elevated levels of humidity; and what did I choose to do? I chose to stand in the Sun from ten in the morning until gone three in the afternoon.
Barmy? Maybe – but I prefer to believe that it was because I had the welcome chance, with three friends from my local amateur astronomy society, SEKAS, to show people our life-giving local star in all its energetically chaotic glory. The event that gave us this opportunity was my local village fête which, despite the uncomfortable weather, attracted large numbers of individuals, couples and families. Some of these lovely people I knew already, others I was meeting for the first time – either way, there were so many of them interested in what we were doing that the four of us barely stopped talking throughout the day. (The exception to this were the necessary times when we tried to keep hydrated; I was glad of the many bottles of chilled water I’d packed into a ‘cool-bag’ … and my sunscreen and wide-brimmed hat.)
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| Back in April I had contacted the Village Hall Committee, who support the annual fête’s organisation. Via our local social media page, I floated the idea of offering a safe solar observing experience. I’d half expected that I’d be told that it wasn’t really the sort of thing for a community fair – but the organisers evidently have a wider vision 😊. As a lovely bonus, the person who replied to my email, Tricia, reminded me that she’d stopped to chat one night whilst walking her dog – I was in my front garden with a telescope, naturally – and that I’d offered some advice on buying a telescope. Apparently, she now owns one … excellent! |
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In the two months between the gift of a south-facing pitch and the fête actually happening I had offers of help and support from fellow members of the South East Kent Astronomy Society – phew! I also tried to prepare the ground a little by posting a few of my own solar images so that people might get an idea of what to expect: “Just to whet your appetites in advance of the Blean Village Fête – at which, clouds permitting, you'll be able to see this sort of thing for yourselves - here's a some images of the Sun taken a few days ago from my garden. We'll have special equipment with us to enable you to do this safely - please, please, please don't look at the Sun directly as you can easily cause damage to your eyes ... and never, ever through binoculars or a telescope as blindness will follow. The whole-disk image was taken using a filter which let's all colours of the rainbow through but reduces the total by 99.999% in order not to damage the camera. Notice the three active regions (aka sunspot groups). Next is a close-up view around one of the sunspots - but this time it's taken using a specialised filter which only permits through one particular wavelength (colour) of light which comes from energised hydrogen. This has the beauty of picking out the chaotic and very energetic surface magnetic field associated with sunspots - just look at those swirls! Do you notice that there are whiter patches to complement the cooler dark sunspots? These are called plages, and they are regions where the surface is hotter than average. The darker loops are prominences that we're effectively observing from overhead. Finally, by over-exposing the disk of the Sun I managed to capture a very impressive prominence: super-hot plasma thrown out into space along the Sun's magnetic field lines. This one is many, many times the size of the Earth.” |
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| Arriving at 10 am, we spent the next hour setting up an array of telescopes and getting their associated bits and pieces powered up. There were three fully automated ‘roboscopes’ in use as part of this array and they attracted a lot of attention. Mostly, this went smoothly – apart from one of my accessories which simply wouldn’t play ball; there’s always one. (Photos by the SEKAS Chairman, Ben Harding, and by the person who has responsibility for the SEKAS observatory site, Ashley Fuggle.) |
We tried to introduce the experience by using a simple Newtonian reflecting telescope with its image projected onto a white background. Not only does this serve to illustrate that the Sun’s native colour is off-white and not yellow, but it revealed the sunspots nicely. (I’ve written about the colours of the Sun before if you’d like more background information: here and here.) Also, by placing a piece of card at the focal point of the telescope and noticing that it starts burning very quickly one immediately sees why looking at the Sun without appropriate equipment is a seriously bad idea. Other telescopes revealed crisp images of our white Sun and the day’s active sunspot regions by filtering out the majority of its light before it even enters the telescope itself. These are called white-light filters because they allow through a tiny fraction of all the colours (wavelengths) of the rainbow.
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| This is a colour image of the Sun taken on the day (by Ashley Fuggle, cropped and augmented by me) using one of the three smart telescopes in use – these impressive ‘roboscopes’, which may be controlled from an app on a smartphone, have a built-in astronomical camera. Each active region (- in this case a sunspot or group of sunspots) is given a numerical designation; for example, the large group centre left is AR-4478. To give you a sense of scale, the blue dot to the left of that region represents the size of the Earth: one could fit 109 ‘earths’ across the diameter of the Sun’s disk. |
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| A highlight of the day for many people was the chance to look at the Sun not in white light but through a filter which eliminated all the wavelengths (colours) of light other than one of the wavelengths emitted by hydrogen, which happens to be a pinkish red. The advantage of this special and highly non-trivial method is that one can observe the flame-like prominences shooting out from the edge of the Sun’s disk. Prominences, the shape of which is influenced by the Sun’s strong magnetic field, are made from the Sun’s matter; in the main, this material falls back into the Sun under the action of its gravitational attraction. Sometimes however, the material has enough energy to break free and to stream out into space as a solar flare – if one of these travels in our direction then, a couple of days later it’ll arrive at our atmosphere and generate the aurora (the Northern and Southern Lights). If it’s powerful enough, we can even see the Northern Lights in the south of England. (Images by Ben Harding, edited by me.) |
All-in-all a lovely, if hot, day for those of us who’d volunteered to offer the experience – and judging by the comments made on the day and on the village’s social media page in the days after, the whole thing was a great success. We’d love to return next year if they’ll have us. In fairness, I ought to share the comment of one person who declared that they’d already seen too much of the Sun and didn’t want to see any more – oh well, it’s not possible to please all of the people all of the time 😉
