Yesterday afternoon's work: a solar obstacle survey from the laundry roof, with a view to eventually putting in a solar water heater for the washing machines.
Step 1: determine what direction true south is. Which means first of all looking up a sundial calendar to look up the time of solar noon (as opposed to local noon, which while always at 12 o'clock, varies in relation to solar noon as we spin and move around the sun. Clear? Not sure I'm explaining this terribly well...) for our specific latitude and longitude is on this specific date. Being the 23rd, only a couple of days after the equinox, this turns out to be 11:59 and 41 seconds. So call it midday then, after all that.
So, now I know that true south is that way, the direction of the sun at 12. (Oh, alright, 11:59.41.) Happily, this is only a couple of degrees out from the way my favoured piece of roof is pointing, so I'm going to simplify things by aligning to the line of the roof instead.

Step 2: Come back after lunch and climb onto the laundry roof. Easier said than done I have to say, though one of my workshop-fellows holds the rickety made-of-odd-bits-of-wood-tied-together-with-rope ladder up for me. Health and safety is a personal option here. The roof is (this time in the afternoon, pretty toasty!) corrugated iron, which offers no handholds, but the rubber of my trainer soles proves friction-y enough. I settle onto my perch on the top of the roof and unpack my useful and hi-tech instruments.

Yup, these are my handy here's-one-I-made-earlier Azimuth Angle and Elevation Gauges. Which, yes, are made of an old cornflakes packet, some thread, and a largish nut.
Step 3: Point my hi-tech instruments at things on the skyline that might get in the way of the sun, and measure their bearings and elevation angles. Threatening thundery noises from those clouds gathering in the east: this roof would be slippery in the wet, so I hurry up a little.
Step 4: Accept the help of a couple of random loitering patient-relatives, who have been watching me quizzically for the last half-hour, in getting back down again with all my things and bones intact.
Step 5: Back at the workshop, transfer beautifully measured skyline onto a chart of where the sun is at any time over the course of the year (it's amazing what useful tools you can find on the internet these days...). Even though I knew as much, it still amazed me how little difference there is between daylight hours in summer and winter, and thus how low in the sky the sun gets.
The upshot of which is that even in winter time the sun clears that big tree at 160° that I had worried might be troublesome. It's looks like we'll get a decent long stretch of strong sunshine in the middle of the day (obviously weather-dependent) most of the year round.

























