Voor Vasilis' pix clock heb ik de zonnewijzer van de achterburen gefotografeerd in infrarood maanlicht.
Maar geeft ie de juiste tijd aan?
Elders op het internet had ik ruimte voor meer karakters en nerdy musings, en dat heb ik hier in de comments geplakt.
Zo cool, die infraroodcamera van jou. En ik kijk er naar uit om die foto in de klok te stoppen.
Ik vond het leuk dat ik beredeneerd had dat dit kon, en dat toen precies zo uitpakte.
Dave doet een Hannibal, qua plan dat 'tezamenkomt'.
Erg mooi trouwens, zo'n foto met een wetenschappelijk verhaal. Schaakmat, platteaarders. Komen jullie maar eens met een voorspelling.
1. Dave commented on 2023/3/8, 10.35 h:
This apartment building has a south facing blind wall. Somebody decided to put it to use, and mounted a sundial on it. I've been waiting for a full moon + open skies to photograph this sundial. Tonight I got my chance. A LED streetlight shines onto this building and throws a motionless shade right into 10 o'clock. But in infrared it is a different story.
The infrared camera blocks light that is visible to the human eye, and passes infrared. Moonlight contains lots of infrared, while LED and SOX streetlights do not. So the shade that the streetlight throws, is not visible in infrared, while the shade that the moon throws, is not overblown by the streetlight. So, in infrared, what you see here, is a moondial.
Does it show the right time?
The moon only moves opposite to the sun when it is full moon. Every day later, it lags nearly 13 degrees behind. Only when full moon happens at midnight, will the sundial be correct.
It was full moon yesterday at 1:40 in the afternoon, so nearly a day and a half ago. That would mean the moondial would lag more than an hour behind.
However, the sundial is tuned to summertime, and it is still wintertime. So coincidentally, today, it was only off by 25 minutes. It pointed at ±11:40 and I took the image at 11:15. Tomorrow at that time, the moondial will point at ±10:50, which is the same margin of error, but to the other side. After that, each night it will be off 51 minutes more, until it is new moon.