I have been watching our tortoises angling themselves at the sun every sunny winter day for a long time now and decided to do some approximate measurements yesterday. Based on this there must be a business idea in the rental of tortoises to installers of solar panels and the like. Inquiries and cost estimates here.
uebero's kleinkramseiten 
Last time I remember you dealing with solar geometry was in your diploma thesis in 1984 (remember that ZX Spectrum little print with shadow plan of your urban block?)
Then, it was the solar water heating hose with plastic bottles.
Now this!
Great!
I wonder what that black tool is on the first photo. Is that the source of the data n the top?
As for the impressive temperature difference between Max and floor, at least part has to do with the dark, absorptive colour of him.
BTW, what is that white instrument at the bottom?
Thank you Thanos, the black instrument is a digital compass (Ed’s sailing gear) and the white sun clock is my Christmas present, from a German company called helios-sundials. The data displayed is from an online solar calculator. Now you are making me go and look for that shading study you did for me in 1984. 💋
Thanx dear for the reply.
So the white toy is a sundial displaying 24 hours? Is it made for polar regions?
Hihi, you can set the latitude to your location, I suppose on the pole you would set it to 90 degrees and read 24 hours (in the summer).