As I was wandering around the site on 2016-03-09 Wednesday (astronomical format of the date is relevant) I noticed the shadows cast by the post brackets and also that it was just a minute or two to noon (UTC) so I took some photos.
The idea is to check the orientation of the house. Obviously it wants to be basically south facing. However, I decided to make it slightly east from that with the idea that it would pick up a bit more energy early in the day when it would be a bit more useful; you have to put energy into a battery before you can take it out. Charging earlier in the day and discharging later should mean that the lowest state of charge reached is typically less deep.
This is partly triggered by memories of my house in High Wycombe which was the north half of a west-facing semi - the east-facing back of the house was heavily shaded by a hill and trees so got little sun in the morning. It was common to need a bit of heat in the morning then to have the house overheat in the afternoon.
However, I think I've overcooked it a bit - it's a bit more round to the east than I intended. I thought that the fence it's against is pretty much grid north-south and that at only 1° west of the grid origin longitude (2° West) that'd be good enough so aligned off that but, on reflection, that 1° probably makes a bit more of a difference than I was thinking this far north and, looking closer, the fence may be a bit off grid north anyway.
Checking with a planetarium program (Stellarium) the sun was actually at an azimuth of 172° at that time. It'd not get round to due south (local solar noon) until about half an hour later so you need to imagine that shadow another 8° to the right.
This is partly because the site is a bit over 3° west of the Greenwich meridian so local mean time is a bit over 13 minutes after Greenwich mean time and also because of the effects leading to the equation of time.
Today and for the next few days local solar noon should be at:
| Date | UTC of LST noon |
|---|---|
| 2016-03-20 | 12:24:16 |
| 2016-03-21 | 12:23:57 |
| 2016-03-22 | 12:23:39 |
…decreasing until mid-May.
It'll be interesting to get a more accurate measurement once all the posts are bracketed vertical by the purlins.
Lesson: if planning to build a house mark out a north-south reference line early in the proceedings on some sunny day well before earth-moving equipment arrives on site.