Daily Archives: March 20, 2015

Sonnenfinsternis

After missing the previous total solar eclipse that was visible in Germany in 1999 due to excessive cloudage in Bonn I was doubly lucky today: There wasn’t a single cloud in the sky, and my timetable at school allowed me to watch the entire eclipse from start (9:29am) to finish (11:49am).

I had a pinhole camera, eclipse glasses and a sun projector at my disposal. Many students also had brought eclipse glasses and/or pinhole cameras, and the beginning of the eclipse happened just before the end of recess, so everyone was keen on taking a first look.

The sun projector proved to be a huge hit as it provided the largest picture of the sun with a diameter of about 5cm; here’s a (bad) photo I took of the projected image around 11:24am, only half an hour before the end of the eclipse:

While discussing the upcoming eclipse with my tenth grade yesterday we noticed the pattern of circles that the sun was making on the classroom floor. I realized that the holes in the blinds act like pinhole cameras and predicted that the circles would turn into crescents during the eclipse, but I think most of the students did not quite believe me until they saw it today – there were rows upon rows of tiny eclipses all over the floor and walls:

One student showed me this photo she had taken and wanted to know why the sun seemed to be whole while the eclipse was visible above and to the right:

It turns out that the sun was still so bright that that its shape was not accurate*, but the lens flare showed the eclipse – how cool is that?

*I know there’s a proper term for this that refers to the fact that when too much energy reaches one pixel it overflows to the neighboring pixels, thus altering the form of the lightsource you’re photographing, but I can’t remember it right now.

Zum Abschluss noch ein paar Links auf deutsch für die geneigten Leser aus der Nachbarschaft:
Sonnenfinsternis am 11. August 1999 und Sonnenfinsternis vom 20.03.2015 (heute), Lens Flare bzw. Linsenreflexion

Besondere Erwähnung verdienen die Sonnentaler – für die gibt es keinen englischen Begriff, so weit ich weiß. Gemeint sind die Lichtflecken, die ein dichtes Blätterdach oder auch kleine Öffnungen in Rollläden/Jalousien verursachen und die heute während der Finsternis als kleine Sonnensicheln zu sehen waren. Die Entstehung beruht auf dem gleichen Prinzip wie die Bildentstehung bei einer Lochkamera.