Night Shining Clouds

1024px-Helkivad_Ööpilved_-_Noctilucent_Clouds_(1)_copy-2

A few weeks either side of the summer solstice is the best time to observe ‘noctilucent’ or ‘night shining’ clouds.

These wispy collections of ice crystals are the highest clouds on Earth, located in the mesosphere up to 50 miles overhead. They’re too faint to be seen in daylight and best observed when the Sun is between -6 and -12 degrees below the horizon.

At the moment at Highland latitudes this gives you an approximate window between 11.30pm and 3am in the morning.

Clear skies.

Scotland – Land of the ‘almost’ Midnight Sun

DSC_0187

A stunning sunset captured over the Isle of Rum

In the north of Scotland we’re about four days away from losing all astronomical twilight and entering a period of sustained ‘nautical twilight’.

During this time the centre of the Sun’s disk never dips more than 12 degrees below the horizon, rendering our clear night skies a dark azure blue, with only the Moon, planets and brightest stars visible after midnight.

This will continue until mid July when astronomical twilight finally reappears.

Contrast this with London, where astronomical twilight continues right through mid summer, producing much darker night skies, but arguably less beautiful and prolonged sunsets.

Clear skies.

Inverness

We’re leaving astronomical twilight behind for several months here in the north of Scotland

London

Significantly darker night skies persist through mid summer in southern England.  Here’s the contrasting data for London.

The Winter Sun at Clava Cairns

DSC_0052

Looking south west from inside the north east cairn at Clava

As a family we have a yearly tradition of heading out for a longish walk on Christmas Eve.  We usually park up somewhere remote in the van, make some bacon rolls then head out along a forest trail or up a local hill.  This year we decided to see if we could catch the setting Sun at Clava Cairns, a beautiful bronze age site located only a mile or so from Culloden battlefield near Inverness.

During my astronomy outreach I’ve given quite a few talks referencing Clava Cairns in relation to the fascinating subject of ancient astronomy.  Often wild speculations are made about many prehistoric sites, in particular Stonehenge, with dubious claims of alignments to stellar constellations or complex planetary cycles.  But one thing is almost universally agreed by archaeologists and astronomers alike, that many of these ancient structures were configured to mark the passage of the solar year.

In Clava’s case, both main passage cairns have mid winter setting sun alignments facing towards the south west, such that for several days either end of the shortest day, the light from the setting Sun will shine down the central passage and light up the interior of the structure.

DSC_0054

Sun rays striking the winter solstice aligned passage.

Of course it’s one thing to read second hand accounts of this phenomena, and quite another to experience them first hand.  As luck would have it, when we approached the site around 3.30pm the Sun was clearly visible and just setting in the south west, allowing us to witness this amazing spectacle and to capture some photographs.

From inside the north east cairn, closest to the main entrance of the site, the passage was already brightly washed over with sunlight.  I was curious to determine if the sun’s position was low enough to light the passage when it was originally covered over (several thousand years ago), so crouched down within the passage to take some of my shots.  Sure enough, the rays of the Sun could be directly sighted down the camera lens.

49021095_10156997855994766_5057786481708367872_o

My daughter Violet standing in the sunlight directed down the main passage of the north east cairn.

The motivation for the astronomical alignment of these structures is still the topic of heated debate amongst historians and archaeologists, but one thing residents of the north of Scotland can appreciate first hand is the depressingly short days and long hard winters we experience at this time of year.  Some sort of large scale and perhaps communal confirmation that the south westerly extreme of the winter sunset (and its associated low midday elevation) had been reached would have been very reassuring to early agricultural societies.

It’s this concept of the Sun both halting its low elevation in the south at midday and the most southern extreme of its setting and rising positions that gives rise to the word Solstice – ‘sol ‘ sistere’ meaning Sun standstill.  The reverse applies during mid summer when the sun rises and sets at its most extreme positions to the north of east and west, and reaches its highest elevation at midday.

zuepze16k9n01.jpg

The two main passage cairns at Clava have south westerly mid winter sunset alignments.

There are some researchers who go much further, and point to alignments between the stones at Clava Cairns with the Celtic cross quarter days and the more complex dynamics of major and minor lunar standstills.  Whilst these may be true it should also be remembered that it only takes two points to make a straight line!  As ever we need to be cautious with our wish to believe, and back everything up, where possible, with evidence.

Marking the Solstice

36088300_1707272335995208_925022512587210752_o

The setting Solstice Sun – Image courtesy of Abriachan Forest Trust

We had a fantastic summer solstice event up at Abriachan last Thursday evening.  Despite being a mid week evening the event sold out and we had a lovely gathering of people joining us to learn all about the solstice and why it was such an important cultural and astronomical marker.

The evening started with a round of Sunset Mocktails, crafted by my wife Judith from a wild fruit concentrate, orange juice and lemonade.  We were also blessed with a lovely sunny evening and enough wind to keep the midges at bay, allowing everyone to mingle and chat outdoors.

35847082_1707279929327782_3426448625834655744_n

A Sunset Mocktail

After waiting for some late arrivals I took the adults and older children into the forest classroom for a talk on the solstice and ancient astronomy, whilst the very young children made flower crowns and Sun mandalas in the greenhouse.

To kick things off I presented a quick ‘what’s up’ guide to June’s night skies and the fantastic collection of planets visible over the next few months – Jupiter, Saturn, Mars and Vesta, the second largest body in the main asteroid belt.

The talk then progressed onto the observational dynamics of the Sun in the sky – its elevation, setting and rising points and the resulting shape the Sun will make when photographed at the same time each day for a year – an Analemma.  We then looked at the reason behind these dynamics (the Earth’s 23.5 degree tilt) and compared our seasons to that of Mars, a world whose 25 degree tilt and highly eccentric orbit produces some of the most extreme seasonal changes of all the planets.

25907420783_5758292f81_b

This is the shape the Sun makes in the sky if photographed at the same time over a year.  Ancient people probably knew about this by instead looking at the shadow projected from a straight object.  Was this shape tied to the mathematical symbol for infinity, or even Pictish and Celtic knot art?

From there we covered the construction of a primitive wooden solar calendar and looked at various examples of ancient solar markers from across the word, including many of Scotland’s mid winter aligned covered cairns (for example Clava Cairns in Culloden).

2652459_bb8198c9

The cairns in Clava have an obvious mid winter sunset alignment and an interesting array of  surrounding stones which raise in elevation towards the South West.

After the talk we broke for more refreshments and it was then over to Clelland for the rest of the evening.

Clelland stared off with a walk and talk describing the various plants which were important during the mid summer months and how the Sun was believed to lend magical power to the plant lore in olden times – boosting their healing and nutritional value.  Everyone then gathered in the green shelter around an open fire as Clelland told a local story to illustrate the way fact and legend are intermingled and passed down through the generations.

35922649_1707272745995167_4595705037824458752_n

As a final gesture towards the setting sun on the longest day folks were asked to write a wish on paper, set it alight and place it in the loch – a reenactment of an old Scots tradition of sending your wishes tumbling into the loch in burning balls of hay!

Feedback on the event has been great and we’ll almost certainly do something again next year. A big thanks as ever to Suzann, Ronnie and the staff at Abriachan for helping make the event so successful.

35633993_1707272612661847_4059858192056713216_n

Making a Solstice wish

Solstice Special at Abriachan

4541761_c3861388

The summer Solstice goes largely unmarked these days. Join me up at Abriachan forest on the longest day to learn all about the Sun’s standstill and why it resonated so deeply with our ancestors.

Join us at Abriachan Forest to celebrate the longest day with a Solstice evening of anicent astronomy and storytelling.

We’ll kick off with a talk from local astronomer Stephen Mackintosh, learning about solar and lunar time keeping, horizon calendars & henges, seasonal constellations and more. Stephen will also give an overview of June’s night skies, including a feast of planetary opportunities and tips on how to get the best views.

We’ll then step back in time and sample the entertainment of our ancestors, as storyteller and countryside ranger Clelland McCallum recounts an ancient tale around the flames of an open campfire.

A warm welcome from the Abriachan Staff with refreshments to toast the Sun’s standstill.  All ages welcome. Tickets are £6 per person. Children 8 years and younger go free.

Booking essential via Eventbrite.  Ticket link here.

Solar Day at Abriachan

We were blessed with a lovely sunny day on Saturday for our day of Solar learning up at Abriachan.  We were fully prepared for indoor activities as forecasts were looking pretty grey.  But as the weekend swung around skies cleared and we ended up seeing plenty of Sun all day.

30171873_1638005529588556_6419296626281205776_o

A day of fun solar learning

Since conditions were so good we moved everything outside, including the talk I’d prepared which was originally put together on powerpoint.  I demonstrated basic shadow time keeping and direction finding, and how solar eclipses take place using a scale model of the Moon and Earth (with the moon’s orbit inclined at 5 degrees).

Based on our model the Earth and Moon were around 3 meters apart with the former about the size of a large orange.  At this scale the Sun would be 10 meters in diameter and over a mile away!  With this model the relative rarity of total solar eclipses becomes clear (on average one every 18 months).

During the talk we also touched upon:

  • Sun gods and how our ancestors perceived the Sun as a perfect orb with no imperfections
  • The human fear of eclipses
  • The discovery of Sun spots and how they revealed that the Sun is spinning
  • How spectroscopy revealed that our Sun is in fact a star (at very close proximity)
  • Why the Sun is loosing mass – over 4 billion tons of hydrogen per second
  • The ultimate fate of our Sun – how it will eventually flare up as a red giant star before cooling and shrinking down to a white dwarf

After the talk Clelland took over for some fun outdoor activities including a scale walk of the solar system, DIY spectroscopes and solar lasers using big magnifiers.  We also did a fun experiment simulating the colour of the sky and sunsets using milk in water bottles.

In terms of solar viewing, I setup the 200mm with a full objective white light filter, and we also had a Sunspotter, kindly on load from Glasgow Science centre.  Both setups produced clear views of the Sun’s photosphere, but unfortunately there were no sunspots to see.  This isn’t entirely surprising given we’re bang in the middle of the 11 year solar cycle minimum, although large spots can appear suddenly at any time.  We hope to one day invest in a good quality hydrogen alpha filter for these events, as these reveal many more interesting features, like edge prominences and coronal loops.

Overall a fun day of learning with great interaction and questions from the adults and little ones alike.