Marking the Solstice

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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.

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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.

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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).

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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.

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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.

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Making a Solstice wish

Solstice Special at Abriachan

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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.

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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.

Mercury Opportunity

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Mercury is only 40% larger than the moon but very difficult to spot

The planet Mercury can be very tricky to observe.  It’s close proximity to the sun means we generally only have brief opportunities to observe it low on the horizon either before or after sunset.

Right now Mercury is approaching maximum eastern elongation (on March 15th to be precise) meaning the planet is up for longer after the sun sets.  The window is still pretty brief with only about 45 mins of useful time to work with after sunset.

Your best chance is to pick a clear evening and head out somewhere with a good unobstructed view to the West.  You don’t need dark skies as the Sun will still be producing a lot of light between 6 and 8pm.

At the moment, and at Highland latitudes, the action starts about 6.30pm just after the Sun sets.  Wait a while then scan the western horizon and you should see Venus first, which will appear brighter.  Use this as a guide for finding Mercury which will sit slightly above it over the next few days.

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6.20pm 14th March 2018, 57 degrees north

The longer you wait after the sunset the easier Mercury will be to see due to darkening skies but also harder due to it moving lower and lower towards the horizon, adding more atmospheric distortion to your views.

If you do see it take a note of its crescent phase.  We almost always see Mercury as a crescent because it would be too close to the sun to see it in a full or new aspect.  One exception to this is during a solar transit when Mercury crosses directly across the disc of the sun.  The next opportunity to witness this will be 11th November 2019, which gives you plenty of time to prepare a solar filter for safe observing of the solar disc.  Happy planet hunting meanwhile.

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Transits reveal the true scale of the Sun

Next Abriachan Astronomy Dates

I’m excited to be hosting two more astronomy events alongside the Abriachan forest team in March and April 2018.  Details and ticket links below.

Star Cluster Special – March 10th (moved from Feb 10th) 7pm-9pm

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The Hyades and Pleiades Star clusters

Explore the great winter open clusters under moonless dark skies with campfire stories to follow. Outdoor binocular guiding under clear skies. Indoor talk, astronomy activities and virtual guiding in the classroom in the event of poor weather. Refreshments provided.

Ticket link: https://www.eventbrite.co.uk/e/dark-sky-observingwith-a-sta…

Solar Special and the Life of Stars – April 14th 2pm – 4pm

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A typical G-type main sequence star – locals have dubbed this one ‘The Sun’

A Sun special exploring our nearest star and the life of giant stars. Outdoor sun projections and activities, with illustrated talk and refreshments. Suzann even has plans for a solar pizza oven!

Ticket link: https://www.eventbrite.co.uk/e/some-sunny-science-and-the-l…

All stargazing events organised in collaboration with the Abriachan team, astronomer Stephen Mackintosh and learning coordinator Suzann Barr. Campfire tales delivered by forest ranger Clelland.

For group bookings please email: abriachanforest@gmail.com

Mercury at Maximum Elongation

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Heavily cratered Mercury

If you have flat and unobstructed views towards the south west there’s a chance of observing one of the most elusive planets this evening – Mercury.

Mercury is hard to see because it orbits so close to the sun, meaning it’s usually lost in the glare of our parent star.

However the planet is currently at its maximum eastern elongation from the Sun, so there’s a small window of opportunity to spot Mercury just after sunset low in the south west. Grab a pair of binoculars and see if you get lucky.

For us high northern latitude observers it’s a tough ask due to the currently flat orientation of the ecliptic, but even if you don’t see Mercury you should catch Saturn sitting just a little higher on the horizon.

Mercury goes through several peak elongations from east to west during a year, providing alternating opportunities to see the planet in pre-dawn or evening skies

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Maximum eastern elongation

Despite being closest to the sun, Mercury isn’t the planet with the highest temperatures – that prize goes to Venus with its thick carbon dioxide cloud base.  This is because Mercury has no atmosphere to trap or distribute heat.  If you were able to stand on Mercury, your daytime temperatures would be a blistering 427C.  However, if you hid in the shadow of a large crater or travelled into the dark half of Mercury, temperatures would plummet to a freezing -173C!  Again, due to a lack of atmosphere to smooth out the temperature extremes.