Sunrise near Saubersdorf 29.4.2021
A clear sky is forecast for the morning. So I set the alarm to 5:20, to be in time for sunrise at 5:40 on the hill with the transponder above Saubersdorf.
First weak light on Schneeberg.
The sun just starts to rise above the horizon ...
... over the dust layer covering Wiener Neustadt and the northern Burgenland.
The sun is up completely now, but it appears oblated, more on its lower half. This is not an optical illusion, but a real optical effect, caused by refraction of the light in the athmosphere, which is more pronounced in the lower layers of the air. Univ. Prof. Hans-Joachim Schlichting, a physician from Münster, who regularly explains natur phenomena in his blog and in the journal "Spektrum der Wissenschaft", on my question has sent me a link with a good explanation of this optical refraction phenomenon - sorry, only in German, but the figure may be helpful anyway.
In fact, says Schlichtung, the sun is still beind the horizon, but its light is refracted and deviated to the horizontal, which makes it visible. The refraction in the lower layers is more pronounced, so the indentation effect is produced.
In the meantime, Schneeberg got a bit lighter ...
... and is colouring to pink-violet now.
Schneeberg and Hohe Wand.
More light on the mountain now, ...
... but regrettably, a thin bank of cloud is drawing in between, ...
... darkening the mountain a bit.
Sun in the foreground however.
Now the layer begins ...
... to lift, and the sun comes back.
...
... gradually gaining predominance.
Lighter now when the sun goes up.
Correspondigly, the mountain gets more yellow-white.
Zooming in on the Schneeberg. The main summit, Klosterwappen, to the left, the Kaiserstein with the Fischerhütte to the right, with the huge snow covered scree of Breite Ries.
Full sun now ...
... and after 1 1/2 hours, I draw back, a bit chilled through.