U3A Stilbaai
VERSKYNSELS ~ PHENOMENA

STRALEKRANS OM DIE MAAN
Deon Begemann het om 02h00 op 10 April 2020 foto's van die maan met 'n stralekrans geneem. Hy skryf as volg:
Die krans word veroorsaak deur maanlig wat deur yskristalle hoog in die atmosfeer gebuig word op die selfde manier as wat jou verkyker lig sal buig. Dit is dus ‘n refraksie proses.
Op die foto’s kan u sien dat daar ook ‘n ligkol rondom die maan is wat die corona (mmm… nie virus verwant nie) genoem word. Die corona word deur maanlig wat van waterdruppels en yskristalle weerkaats word, veroorsaak, op dieselfde manier soos wat ‘n spieël lig weerkaats. Dit is dus ‘n diffraksie proses. Die sentrale ligkol voor die maan staan as die areola van die corona bekend.
Om hierdie optiese verskynsel te kan waarneem moet die ys en water op ‘n sekere hoogte voorkom (5-10km) daarom is dit redelik skaars. Dit kom gewoonlik voor as daar koue lug in sirrus wolke oor die land beweeg met die gevolg dat dit gewoonlik weersverandering vooruit loop. Twee dae later lyk die weer al klaar heelwat anders as die Vrydag.
Die stralekrans is gewoonlik baie groot en oor 22° van die waarnemer versprei. ‘n Fyn reënboog kan soms gesien word met die rooi lig aan die binnekant en blou lig aan die buitekant van die sirkel. Die binnekant van die sirkel is effens donkerder omdat die lig van die maan weg van die waarnemer gekaats word.
Die fotografie was ingewikkeld en die outomatiese stelling wou nie mooi foto’s genereer nie. Die beste resep was as volg; Gebruik ‘n driepoot, stel kamera op Manual, stel fokus op oneindig (∞), F- waarde op 2.8, ISO stelling op 800 en die lens
opening tyd op 1 sekonde. Aktiveer die kamera se tyd vertragings meganisme en laat die kamera self die sluiter laat afgaan om bewerasie uit te skakel. Speel met verskillende foto redigering opsies wat in jou kamera ingebou is (Retouch) of op jou rekenaar.
Hieronder is ‘n reeks foto’s wat uit een foto geredigeer is.

HALO ROUND THE MOON
At 02h00 on 10 April Deon Begemann took photos of the moon with a halo. He writes as follows:
 The Halo is caused by moonlight that is bend by ice crystals high up in the atmosphere in the same way that binoculars bend light. Therefore it is a refraction process.
On the photos you will see that there is also a ball of light surrounding the moon called a Corona (mmm... no virus connection) The corona is formed when moonlight is reflected by water droplets and ice in the same way a mirror reflects light. Therefore the process is called diffraction. The central part of the ball of light is called the aureole.
To be able to see this optical phenomenon, ice and water have to be present high up in the atmosphere (5-10 km). This does not occur too often. It usually happens when cold air in cirrus clouds passes over the land followed by a change in weather. Two days later and the weather has changed considerably since the Friday.
The halo is usually very big and stretches over approximately 22° from the point of observation. A slight rainbow can sometimes be seen with the red band inside the ring and the blue on the outer side. The inner part of the circle is slightly darker because the light from the moon is reflected away from the observer.
Photographing the ring was not easy and the automatic setting of the camera was disappointing. The best recipe was as follows; Use a tripod, set the camera on Manual, adjust the focus to infinity (∞), F-value on 2.8, ISO setting at 800, and lens opening time at 1 second. Activate the camera timer trigger to take the photo after a few seconds in order to get rid of any shivers. Play with your camera editing software by utilizing the Retouch facility or use you computers editing program.
Below is a series of photos edited from one single photograph taken.

Foto van maan geneem om 02h00 op 10 April 2020  ----  Photo of moon taken at 02h00 on 10 April 2020.
Maan stralekrans -- Moon halo
Hierdie artikel en die foto's is beskikbaar as 'n pdf dokument, klik hieronder om dit oop te maak.
Daar was 'n stralekrans om die maan.  (12 April 2020)
This article and the photos are available as a pdf document, click below to open it
There was a Halo around the moon.  (12 April 2020)

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