Atmospheric Optics

Fine examples of sundogs and part of a 22-degree halo captured by member Jim Buchell on the 25th September 2023 from Dartford.

”A sundog, also known as sun dog, mock sun or parhelion, consists of glowing spots around the sun. They are created by sunlight refracting off plate-shaped ice crystals in the cirrus clouds. Sundogs are some of the most frequently observed atmospheric optical phenomena and can be observed throughout the year and anywhere in the world. They are also associated with 22-degree halos.

Sundogs tend to be most visible when the Sun is close to the horizon. The part of a sundog closest to the Sun tends to be red in colour, while the areas further away from the Sun generally appear blue or green.” Ref:https://www.timeanddate.com/astronomy/optical-phenomenon.html

For more information about sundogs and 22-degree halo’s check out https://atoptics.co.uk/blog/sundogs-sun-dogs-parhelia-mock-suns/ and https://atoptics.co.uk/blog/22-halo-formation/

Whilst travelling early morning on a train to London, CMHASD Chairman John Archer saw this fine example of a sun pillar on the 23rd October 2023. 

”Sun pillars and light pillars are beams of light that extend vertically upward (or downward) from a bright light source, such as the sun or another bright light low on the horizon. They can be 5 to 10 degrees high and sometimes even higher. In fact, they might lengthen or brighten as you gaze at them.  They’re beautiful and wondrous. And they’re also the source of some UFO reports!

When is the best time to see them?

You’ll most often see sun pillars when the sun is low in the western sky before sunset, or low in the east just after the breaking of dawn. However, you might even see a sun pillar when the sun is below the horizon. On the other hand, you can see light pillars at any time of night.  They’re called sun pillars when the sun helps make them. But the moon or even streetlights can create this light phenomenon, too, in which case the name light pillar is more appropriate.” Ref:https://earthsky.org/earth/what-is-a-sun-pillar/

For more information about sun pillars see Les Cowley’s brilliant website Atmospheric Optics .

A lovely image taken by member Honor Wheeler on the 10th August 2023 whilst at the pavilion on an informal night of some crepuscular rays.

”Crepuscular rays are sunbeams that originate when the Sun is just above or below a layer of clouds, during the twilight period; which extend over the western sky radiating from the position of the Sun.  Crepuscular comes from the Latin word crepusculum meaning “twilight”.  Loosely, the term crepuscular rays is sometimes extended to the general phenomenon of rays of sunlight that appear to converge at a point in the sky, irrespective of time of day.” Ref: https://en.wikipedia.org/wiki/Crepuscular_rays

”The radiating appearance of the bands is caused by perspective, as demonstrated by the fact that when on rare occasions the rays extend across the entire sky, they appear to converge again on the eastern horizon. This rare related phenomena are called anticrepuscular rays and so appear at the same time (and coloration) as crepuscular rays but in the opposite direction of the setting sun (east rather than west).” Ref: https://www.britannica.com/science/crepuscular-ray

Noctilucent clouds put in a rare appearance on the 5th July 2023 from around 10.50pmish until 11.30pm and a few lucky CMHASD members got to see them 🙂

Below are the photos that members Jim Burchell, Diane Clarke, Martin Crow and Sonia took of the clouds.

Jim’s NLC images, taken with a Pentax KP.

Diane’s NLC image, taken using a Canon M50 Mk2, lens Canon 100mm macro, f3.2 @ 2.5sec, ISO 400.

Martin’s NLC image, taken with an iPhone.

Sonia’s NLC images, taken with an iPhone.

Noctilucent cloud spotted on the 30th June 2023 around 3am BST by members Martin Crow and Sonia. Both photos taken using an iPhone.

Martin’s image taken from Essex

Sonia’s image taken from North Kent

Rare Noctilucent Cloud spotted by CMHASD members Diane Clarke, Martin Crow and Sonia on the 25th June 2023.

First image below was taken by Diane using a Panasonic camera DMC-TZ100, f2.8 @ 1/10sec and ISO 6400 at 11.22pm BST.

The next two images were taken by Sonia using an iPhone 8 at 11.04pm and 11.14pm BST.

The next image was taken by Martin Crow using an iPhone.

A great example of a fogbow captured by member Kevin Smith on the 7th May 2023.

A fogbow is a similar phenomenon to a rainbow but as its name suggests, it appears as a bow in fog rather than rain. 

Due to the very small size of the water droplets that cause fog being so much smaller than in rain i.e. smaller than 0.1 mm in diameter; fogbows have very weak colours or no colour at all.  Fogbows that have no colour are sometimes called ‘white rainbows’.

A Fog Bow by Kevin Smith

NEVER LOOK AT THE SUN DIRECTLY. Please see our Solar Observing safety page at crayfordmanorastro.com/solar-safety/

A splendid example of a Sun halo captured by CMHASD Chairman John Archer on the 30th April 2023.

A Sun halo is caused by the refraction, reflection, and dispersion of light through ice particles suspended within thin, wispy, high altitude cirrus or cirrostratus clouds.

CMHASD member Jim Burchell captured this superb Sun Halo on the 14th Dec 2022 around midday which lasted for quite a long time – over an hour. A Sun halo, also known as ’22 degree halo’, is an optical atmospheric phenomenon that occurs due to sunlight refracting in millions of hexagonal ice crystals suspended in the atmosphere. 

More information about how Sun Halo’s are formed can be found on the Atmospheric Optics website.

A shinning example of a Sundog captured by member Martin Crow when out and about on the 20th Nov 2022.

A Sundog (or sun dog) is an optical atmospheric phenomenon that causes a bright, rainbow-colored patch of light to occur on either side of the sun or both sides at an angle of 22 degrees.  Sun dogs occur as a result of the refraction or scattering of light from flat hexagonal-shaped ice crystals that are suspended in clouds.

In the most brilliant displays, when 2 Sundogs appear, it’s as if there are now three suns in the sky — the main sun and two little siblings.

These “side suns” are colloquially known as sun dogs, officially known as “parhelia,” which is Greek for “next to the sun.”