Sun Watch at Abbot Hall

As part of the International Year of Astronomy, 2009, Stuart Atkinson and the Eddington Society arranged a public solar observation session for earlier today. Remarkably, the grim and grey weather that had been parked over here for a while took a brief holiday, allowing the Sun to shine freely aside from the odd relatively fast passing cloud.

The wind blew up on high, but like on other solar observing sessions I’ve been to, the warmth of the Sun was soon on us and members of the public gathering round. Nearby teenagers, families moving through and even the odd guest from a nearby wedding came over to have a look. And a variety of instruments were provided for them to do so.

Robin Leadbeater, of Cockermouth Astronomical Society, brought over a couple of his own instruments. Stuart brought over his telescope, which he used to project the Sun’s disc in white light. This is a good general method for observing the Sun and can be done through a pinhole in a box or with any small instrument, taking great care not to look or be in a position where you may even glance as the Sun directly or through the instrument.

When the Sun is active, this method allows Sunspots to be seen. However, the Sun is not at that part of its elevenish year cycle, preferring instead to be spot free today. To view anything of interest in this situation, you need some serious hardware, and this is where Robin’s two instruments come in.

The first instrument, shown a couple of pictures above, is the spectroscope. This splits the white light of the Sun into its rainbow of colours. These are shown as a strip and then magnified to give a view of a small part of the spectrum at high resolution (eg the image above). Dark lines can be seen – the fingerprints of elements absorbing the sunlight either in the solar atmosphere or in our own. If you could stretch out a rainbow so the colours were well separated, this is what you would see, one and a half centuries after it was first discovered.

The next instrument brought to us by Robin was his Coronado Personal Solar Telescope, a favourate amongst amateurs wanting to look at the features of the Sun. This selects a single slither of colour – in this case the Hydrogen Alpha wavelength of light in the red part of the spectrum – and allows you to directly view the Sun’s emissions in this light. As all of the light in the rest of the Sun’s colours has been filtered away, it is dim enough to see directly.

The view of the Sun through this solarscope is one of the outer layer of hydrogen (other Coronado PSTs or settings of them allow some other layers to be seen). The mottled surface of the Sun can be seen (due to supergranulations, clusters of granules on the Sun’s surface, each of which are convection cells where hot gas rises to dump energy and sink again). The outer corona can be seen (as in a total solar eclipse, the outermost thin layer of gas) and any prominences, flares and the like can be seen – there are some to the bottom of the image above.

Of course with so many people around, there were those who came to observe and some who decided to stay after hearing about the society. Some took a leaflet for the new exhibition – Our Amazing Universe – which runs at Kendal Museum on Thursday, Friday and Saturday from 12-5pm until January the 30th.

The event ran for two hours from 2pm until 4pm, after which we all packed up, said goodbye and headed our separate ways. Even the Sun, which within the next couple of hours was shrouded entirely out of view. Another success for the society. Stuart Atkinson’s initial impressions and pictures can be read here and all the photos I took can be seen here.


One response to “Sun Watch at Abbot Hall

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