Total Lunar Eclipse

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This Friday (the 27th of July) the Moon will rise into view in the south east around 9.30pm with an unusual red colour. This is due to a rare phenomena known as total lunar eclipse – when the Earth sits directly between the Moon and the Sun.

But why doesn’t the Moon darken if its light supply is cut off by the Earth, and why will it turn a red colour?

The best way to think about this is to imagine yourself standing on the surface of the Moon as the Earth slowly passes in front of the Sun.

As the disc of the Earth begins to occult the Sun it will start to darken until finally the whole of the Earth sits in front of the Sun. But as this takes place something amazing happens. The Earth’s atmosphere refracts the sunlight into an intense circle of vibrant sunset. It’s this ring of fire around the Earth that illuminates the Moon during totality, giving it an eerie red colour.

This far north between 9.30pm and 10.30pm it’ll still be pretty bright outside but the colour change should still be obvious to see. As the evening progresses the eclipse will become partial and will be almost over by midnight.

Totality for this lunar eclipse will be 103 minutes making it the longest in this century. As my animation below shows we won’t be able to witness the start of this eclipse, only its middle and end.

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Times:

Peak Eclipse 9.21pm
Moonrise (at 57 deg north) 9.35pm
Total eclipse ends 10.13pm
Partial eclipse ends 11.19pm
Eclipse ends 12.28am

Clear skies and happy Moon watching!

 

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

Spica and the Precession of the Equinoxes

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A line of the Moon, Jupiter and the bright star Spica can be seen tonight in the S/SW as the Sun sets (try after 11.30pm or later if it’s still too light).  Spica is the brightest star in the constellation Virgo and was the star that helped unearth the 26,000 year cycle known as the Precession of the Equinoxes.

As the story goes a temple in Thebes built around 3000 BC was originally aligned with Spica but the Heliacal sighting was found to have significantly drifted off target some 3200 years later.  This fact was taken up by the Greek astronomer, mathematician and geographer Hipparchus who used this and other data to approximate the precessional cycle time of the heavens (as he saw it) to be over 30,000 years.  An over estimate but a respectable first guess.

Of course we now know the real reason for this apparent cyclic drift of the constellations over long time scales – 25,772 years to be accurate.  A wobble in the earth’s local axis of rotation (see animation below) caused by the gravitational influence of the Moon and Sun on Earth’s equatorial bulge.

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There are a couple of interesting side effects of this dynamic.  Firstly our pole star slowly changes over thousands of years.  In ancient Egyptian times (3000 BC) the northern  pole star was Thuban in the Constellation Draco, and in around 12000 years time the pole star will have moved close to brilliant Vega.

The other effect is that the dates of the original Zodiacal star signs are now completely out of sync with the position of the Sun. A child born today (June 24th) is still designated as a ‘Cancer’ (because the Sun is supposed to be in the constellation Cancer right now).  But the Sun isn’t in Cancer – it’s actually in Taurus.

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.

Super Blue Blood Moon

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So what’s a ‘Super Blue Blood Moon’?

It’s a combination of three lunar phenomena. A blue moon is when two full moons fall in the same calendar month, which isn’t very often (roughly once every 3 years) hence the expression ‘once in a blue moon’. The ‘super’ is because the full moon is occurring at a close approach to earth (formally within 10% of orbital perigee). Finally the blood part indicates there’s also a lunar eclipse, although we won’t witness it from Highland skies.

One of the amazing things when witnessing a lunar eclipse is the blood red colour the moon takes as sunlight refracts around earth’s atmosphere.  This is really an extreme form of earth shine, when we can see the shadowed areas of the moon due to sunlight reflected from earth.  I always like to imagine what a lunar eclipse would look like from the surface of the moon.  As the earth completely obscured the sun you would see a brilliant ring of red light radiating around the black disc of the earth.  The lunar landscape around you would be bathed in an eerie red light.

The blue moon phenomena is interesting when you consider we now use a solar calendar.  Around 40BC Julius Caesar severed the old link with the moon, so that months (or ‘moon-ths’)  no longer coincided with the phases of the moon.

Lunar Burns Night

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The star of the evening – a waxing gibbous moon

What do you get if you cross a bright gibbous moon, award winning haggis and a celebration of Scotland’s bard?  A Lunar Burns Night!

This was our fourth stargazing event up at Abriachan and despite somewhat blustery conditions, ended up being loads of fun with a good turnout across all ages.

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Haggis and neep hand warmers

After introductions from the Abriachan crew we kicked off outside with the moon high in the south and making dramatic appearances between fast moving clouds.  After a bit of moon gazing and chat I took everyone back inside the forest classroom for an illustrated talk on the moon – its phases, cycles, observational phenomena and even some discussion on manned moon bases (why the obsession with Mars when we could be building a lovely moon base at much lower cost and risk?).

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Presenting my moon talk

After the talk Roni and Suzann called everyone through for Clelland’s dramatic ‘knife wielding’ address to the Haggis, followed by a tasty spread of haggis and neep wraps.  The younger ones then took centre stage as they expertly simulated millions of years of lunar surface evolution – by dropping (never throwing!) metal balls into giant flour trays.  This was followed by 3D moon phases and a competition to see who could guess the real separation between the Earth and Moon.

Clelland addressing the haggis

Addressing the haggis

The evening was topped off up with a haggis drive and Cottar’s tales from Clelland.  I also took a group out for some final moon gazing, and managed to glimpse a few brighter stars between the cloud breaks.

The only disappointment was being unable to set up the video telescope to show folks closeups of the lunar surface.  The sporadic showers and wind made that too challenging on the night, but I don’t think anyone really noticed.

 

We have more astronomy nights planned at Abriachan before the encroachment of our long summer days.  On March 10th we’re hosting a Star Cluster special under dark sky conditions, followed by a Solar Special on April 14th, where we’ll hopefully be projecting the Sun onto a big screen for all to see.  For details please check Abriachan’s or my own Facebook pages.  As ever thanks to the Abriachan team for helping make these events so fun and welcoming.

Clear skies!

 

Lunar Maria

Happy New Year everyone.  There’s been a lovely bright full moon on display over the new year, allowing me to venture out for well lit evening walks, stopping every so often to study the bright lunar disc both unaided and with binoculars.

One very obvious thing you can notice from looking at the moon, especially naked eye, is the contrasting dark and light regions.

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The dark regions are called lunar ‘maria’ which is latin for ‘sea’. These regions are relatively smooth and have a low abundance of craters, which suggests they’re younger than the brighter more heavily cratered regions.

But how can the moon, a dead world with no significant geological activity, have younger regions?

The answer is from giant impacts.

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Imagine a massive asteroid hitting the moon. Not only will it generate a huge crater but the heat from the impact will cause the solid rock underneath to become molten and well up in a huge overflowing lava event. This overflow pours across the surface of the moon a bit like applying fresh plaster to a wall, masking all the old craters and creating what we now see as ‘maria’.

I’ll be talking about this and much more at our special moon night on the 27th Jan out at Abriachan Forest.