Mercury, Moon, and Mirages


Rising and Distorted Supermoon on New Year's Day

Happy New Year to all!  

New Year’s Day proved to be a busy one for sky sights from home in southern Alberta.

Clear skies and warming temperatures allowed me to capture a trio of sights on January 1: Mercury in the morning, a unique mirage called the Fata Morgana in the afternoon, and the rising Full Moon in the evening.

On January 1 elusive Mercury was at its greatest elongation away from the Sun in the morning sky. This placed it as high as it can get above the horizon, though that’s not high at all at the best of times.

Mercury in the Morning on New Year's Day
Mercury at dawn in the southeast sky.

I captured Mercury before dawn as a bright star in the colourful twilight, using a telephoto lens to frame the scene more closely.

At this time the temperature outside was still about -24° C, as a cold snap that had plunged the prairies into frigid air for the last week still held its grip.

But by the afternoon, warmer air was drifting in from the west, in a Chinook flow from the Rockies.

As evidence of the change, the air exhibited a form of mirage called the Fata Morgana, named after the sorceress Morgan le Fay of Arthurian legend. The illusion of castles in the air was thought to be a spell cast by her to lure sailors to their doom.

Fata Morgana Mirage on the Prairies
A Fata Morgana mirage on the Prairies

The mirage produced the illusion of bodies of water in the distance, plus distorted, elongated forms of wind turbines and farm buildings on the horizon. The cause is the refraction of light by layers of warm air aloft, above cold air near the ground.

By evening the mirage effect was still in place, producing a wonderful moonrise with the Full Moon writhing and rippling as it rose through the temperature inversion.

As the lead image at top shows, at moments the top of the disk had a green rim (almost a distinct green flash), while the bottom was tinted red.

Here’s a short time-lapse video of the scene, shot through a small telescope. The lead image above and below is a composite of four of the frames from this movie.

Rising and Distorted Supermoon on New Year's Day
A composite of 4 exposures of the rising Full Moon on New Year’s Day, 2018, rising from left to right over a snowy prairie horizon in southern Alberta. This is a composite of 4 out of 500 images shot for a time-lapse sequence, layered in Photoshop. All were with a 66mm f/7 William Optics apo refractor and Canon 60Da camera firing 1/25th second exposures every 1 second.

This was also the largest and closest Full Moon of the year, what has become popularly called a “supermoon,” but more correctly called a perigean Full Moon.

A lunar cycle from now, at the next Full Moon, the Moon undergoes a total eclipse in the dawn hours of January 31 for western North America. This will be another misnamed Moon, a “blue Moon,” the label for the second Full Moon in a calendar month.

And some will also be calling it a “supermoon,” as it also occurs close to perigee – the closest point of the Moon to Earth in its monthly orbit – but not as close a perigee as it was at on January 1.

So it will be less than super, but it will nevertheless be spectacular as the Full “blue” Moon turns red as it travels through Earth’s shadow.

— Alan, January 2, 2018 / © 2018 Alan Dyer / amazingsky.com

 

The Green Flash – At Last!


The Green Flash (Nov 15, 2013) from Barbados

At last, I enjoyed a successful attempt to capture the elusive green flash.

During three weeks at sea attempts almost every evening from the ship to sight the green flash always failed, as the Sun set behind low horizon cloud.

But this night, the Sun set into the ocean with a clear horizon. My location was a small public oceanside walkway on Bay Street near Bridgetown, Barbados. It was a great spot to watch the sunset, though our main purpose for stopping there was to pick up some fried chicken at the KFC just steps away!

But the imminent sunset under ideal conditions made it worthwhile sticking around to see if we (I was with two friends from Alberta) could sight the green flash.

We did! I shot a rapid fire sequence – the image above is one frame of many catching the last bit of the Sun remaining above the horizon and turning green.

The infamous green flash is a refraction effect caused by the atmosphere separating out the green light and lifting it higher so it’s the last thing you see as the Sun sets. Conditions aren’t always amenable to seeing the green flash – you need a clear horizon and you also need the atmosphere structured with warm layers near the sea creating a mirage effect.

For more details on the technical explanations see Andrew Young’s page at http://aty.sdsu.edu/ 

… and Les Cowley’s page at http://www.atoptics.co.uk/atoptics/gf1.htm 

Andrew Young has a nice simulation at http://aty.sdsu.edu/explain/simulations/inf-mir/inf-mirSS4GF.html

Sunset from Barbados (Nov 15, 2013)

This was the view moments before, with the lower edge of the setting Sun distorted by atmospheric refraction, a sign that you might see a green flash as the upper edge disappears.

Sunset & Sailing Boat from Barbados

I shot this image a few minutes earlier as a photogenic sailboat drifted into the scene. Red sails in the sunset!

I’m nearing the end of my stay in Barbados and my 4 weeks away from home. There are heavy snowfall warnings out for southern Alberta this weekend so I’m not anxious to return! But winter will be waiting for me next week.

– Alan, November 16, 2013 / © 2013 Alan Dyer