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Making a solar compass Answered

I realized a while ago that if you put something on a rotating  mount inclined to your latitude and adjust up or down for the inclination of the sun (up or down from its equinox path) for that day of the year, you have a compass.
For instance, today the sun is just over 23 degrees off its equatorial path. So you have a stick pointing straight out from the mount at a right angle and you just angle it down by 23 and a half degrees.
So you tighten it in place at that angle.   Next you combine rotating the entire thing on the ground (keeping your latitude angle correct) and you rotate the mount itself until the stick points straight at the sun.  At this point, no matter where you are on earth, your mount is inclined in line with north/south. 
I have 2 little test compasses to try this but it was fully cloudy all day  so I cannot try it out.
One uses a Fresnel lens and the other uses a magnifying glass to line up the sun.
Just wondering if anyone else has done something like this?  Solar compasses did exist and I had a look today.  They do not look like my thing at all.  They look really complicated!
I will post a year of inclination data shortly.
Thanks Brian


I tried out the first one and (because of wiggles and waggles in the axis, and difficulty measuring the degrees of inclination accurately, it was only accurate to about 10 degrees. 
I believe Mark 2 is much better.  It is also much easier to make.  You might even have all the parts right now.
I would really like it if people give it a try. Here it is

Interesting piece of kit. Having seen it and thought about more, you've got the time of day built into this with the chart and position data.


http://en.wikipedia.org/wiki/Solar_compass Thanks, I think this is the case. I found the link to a solar compass that was patented in 1836 last night!
But, I think  my explanation is more understandable.
Having made the first one, I think the next ones will be a lot easier (and a lot smaller and a lot different). 
Really, all you need is a few pieces of ply wood, hinges, the chart and a little protractor or photocopy of protractor.
(But it is so hard for me to visualize this before I make it).
Supposed to be cloudy all day again.  Darn!
Thanks for your interest.

That was good to read, thanks. I see there there is a local-time adjust.


You do need to have the right time though.
If you think of marine navigation with a sextant, a ship's clock is essential. There you're doing a related operation to find latitude.
At a fixed location you can mark north and leave it, for portable you'd need to know your time and position?


I checked it out and I think you are half right. There are 2 possible answers but if you recheck 20 minutes later, one north will have moved and one will remain in exactly the same spot.
I hope!

Nope, I think all you need is the inclination of the sun on that day and the latitude angle. These angles are kept constant.
The only things you are allowed to adjust are the direction that the latitude angle is pointing and you are allowed to rotate the thing that is on the latitude angle too.
There is only one combination of those adjustments that will point at the sun.
Once you get it pointed at the sun, you can read off the solar time if you have a protractor set up to do that on the latitude axis.
Its pretty neat actually (if it works).
Total cloud cover right now (and I have not fully made it) so very little chance of testing today.
I might be able to post pictures though.
Thanks for the interest

The sun as I see it has a time-of-day inclination variance. I think you'te compensating with the latitude angle, is that it? (getting it slowly I think)


Well today I finished it off but still no sun!
So I decided to test inside using a light as pretend sun. One little problem. There are 2 possible norths!
I don't think it is a big problem. One should be stationary and one will move.
(The moving one is not the real north). So if you have a good idea what time of day it is, no problem. But if you have no watch or it is near solar noon then 2 readings half an hour apart should clear up any doubt.
I actually have 2 prototypes and they are quite different.
If this works well and solar compasses become something used and useful, they will probably look nothing like my prototypes.
(Just so you know)

http://www.powerfromthesun.net/chapter3/Chapter3Word.htm (I have adapted his graph and I have permission as long as I give a link. The attached picture shows a bit of what I mean. Basically you are setting up equatorial mount.
I believe most people find north south BEFORE they set it up.
(And it is critical to find it). But if you know the inclination AND your latitude, and set them up accurately enough, you can use the mount itself to find the north south line , simply by pointing at the sun!
Anyway, thats the theory.
Will it work in practice?