Re outdoor installation ...
I purchased a little waterproof/UV stabilised box. Drilled a hole for the 1-Wire cable, and 2 tiny holes for the diode legs. I cut the diode off the board and mounted it on the outside top surface of the box, then rejoined the diode to the board. I sealed the holes with a dob of silicone.
This worked for a while, but I found that the sun was too bright and saturated the diode during the middle hours of the day. So the next mod was to insert a resistor in series with the diode to reduce the current.
This worked perfectly for a few months ... but then the diode died completely. I don't know whether it was excess solar radiation, some other environmental issue, or just bad luck.
Anyway, I'm now awaiting a new diode ... I have rebuilt the box a little and this time I plan to do the ping-pong ball trick as an attenuator. I have cut a hole in the bottom of a ping-pong ball, and will position the new diode approximately at its centre. I'm guessing the ping-pong ball might need replacing every year or two.
Will this work ? Who knows ... with luck I'll put it back into service this coming weekend.
Re-calibration ...
The best I could do was to guess that the solar radiation was approx 1000W/sqm at noon on mid-summers day under a perfect clear sky. This is just a guess.