25th December 2015 Solar and Lunar events at Sighthill Stone Circle

by Duncan Lunan - 09:45 on 19 October 2015





25th December 2015 Solar and Lunar events at Sighthill Stone Circle


In September and October 2015 the Moon has been at its Minor Standstill, at the intermediate points between the extreme positions of its 18.61 year cycle.   At the stone circle which I built in Sighthill Park in Glasgow in 1979, the first astronomical one in the UK for over 3000 years, these are the only events marked by the stones which have never been observed and photographed.   A year either side of the standstill would be accurate enough for photographic purposes, but there has still been only one success in trying to catch the Moon at its furthest north and south each month.   The removal of the circle for the area to be redeveloped was scheduled for December 2015, although the City Council has promised that efforts will be made to remove the stones intact and reposition them elsewhere.   But the best chance this year to photograph two of the other three minor standstill events will be on December 25th, just after the solstice, and I have asked the Planning department for the stones to remain in place till then.


As it happens, on December 25th the Moon will rise and set in its northerly minor standstill positions, over the marker stones, and it will be a Full Moon, so the events will take place around the time of sunrise and sunset.   Furthermore, the Moon will be at its closest to Earth for the month  (at perigee)  on the 21st, so although the Full Moon on the 25th December won't quite be a 'supermoon', it will look particularly big and bright when near the horizon.   The position of the Sun on the horizon hardly changes for three days before and after the winter solstice, which this year is on December 22nd, so on the same day the Sun will also rise and set over the relevant marker stones in the southern arc of the circle.


Normally the Full Moon rises roughly as the Sun sets, but in this case the Moon is far in the north and the Sun far in the south, so our northerly location makes a bigger difference than usual.   According to Heavens-Above.com, on December 25th the Moon will set in the northwest at 07:55 hrs.   The Sun will rise at 08:45 hrs.   The Sun will set at 15:50 hrs and Moonrise in the northeast will be at 16.50 hrs.   However those times are approximate because they are calculated for a true horizon and don't take atmospheric refraction into account.   From the heights of the horizon we can therefore predict that the Moonset will be slightly earlier, the sunrise will be roughly on time, sunset will be slightly earlier, and the Moonrise will be slightly later;  but experience has shown that air temperature and other atmospheric conditions can change the times still more.


The plan is therefore to make a day of it, weather permitting, and have lunch somewhere nice in the course of it.   There is a chance that the circle will have a great astronomical finale at its present location, so if the weather is any good we intend to be there for the rises and sets, and all friends will be welcome.


If you are interested in joining us please call Duncan on 01292 739014  or e-mail  duncanlunan@talktalk.net for full details.




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