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.
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.
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! At this scale 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 showed that our Sun was in fact a star (in 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 and briefly 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 currently bang in the middle of the 11 year solar cycle minimum, although large ones 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 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.
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.
Transits reveal the true scale of the Sun
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
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
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: firstname.lastname@example.org
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
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.