Heliostat questions and finding north with a heliostat?

I play around with solar "research" in my back garden. But it slopes to the north and this means that I have no play in the winter. Sun is gone. Now it is on its way back and starting to visit again. I tried and failed to make a heliostat last year. In the process of researching, I found old heliostats from the late 1800's that were clockwork. Kinda like what I wanted to do. But I was clueless in my understanding of them. I got 2 reports that a heliostat will work if a mirror is on equatorial mount and turning at one revolution every 48 hours and light can be sent almost anywhere(in the southerly direction) from the mirror. So 3 or 4 of these boys could be used to concentrate the light in one area. There was big argument about it last time and it remained unresolved. So I have just started a test of the concept on sunday. I only got 2 hours in but it did seem to work! My mirror is not powered. I just set up a little mirror on an equatorial mount with degrees calibrated underneath so I could turn it 7.5 degrees and see if the light still shines in the same spot. If it works, it can probably also be used to accurately set up equatorial mounts! It is hard to point it exactly due north. Wobbles in the reflected light from the mirror over the course of a day might tell us where north is! I will show my apparatus soon. Brian

gaiatechnician (author) 8 years ago
I have been looking into the heliostat on equatorial mount with a 48 hour rotation but I have not been able to conduct proper experiments due to clouds. It seems to come close but is not exactly right. Even if the 48 hour rotation does not work perfectly, it may be part of the solution. If it is "nearly right" then all that is needed is a 24 hr rotation for the sun pointer to make fine adjustments to the angles of the mirror! You piiggy back this onto the 48 hour rotation that is nearly right. This means no huge swings on the gimbal (perhaps a small ball joint is all that is needed). Like the ball joint in a tractor 3 point linkage. What do you think? It could be weeks before I get the time and sunny weather to test this. Any takers? The biggest problem with the 24 hour rotation is the gimbal has to swing so much at certain times of the day. If you piggy back, the swings are going to be tiny. I think it will work. Brian
kelseymh8 years ago
If you do get your apparatus to work (or even if you don't!) please consider documenting it as an Instructable. This is an excellent science project. You suggested that the wobble, or variation in reflected position could be used to determine true north. That is certainly the case, and is a variation on the old Scouting method of determining north with a sundial (shadow stick). In the Northern Hemisphere, local noon occurs when the Sun is due north. Using a sundial, you can track the position of the shadow tip over a day, as it sweeps from west to east. The point where that tracking line is closest to the sundial vertical is local noon, and the line from that point through the sundial axis is north. You should be able to do something similar with a heliostat, though of course the angle of the mirror will need to be included.
gaiatechnician (author)  kelseymh8 years ago
I published! But it is not much of an instructable so maybe you can check it out before they unpublish it.
(I might not get any results for quite a while because I have a backlog of work and my gf is sick in hospital) so please (anybody) do your own if you have time.
It is pretty simple but it took an age to make it that simple!
Thanks! It won't get featured, but it also won't be "unpublished." There are no "quality" criteria at I'bles, other than a minimal requirement that all steps have associated image(s). What you've done is certainly good enough as a starting point. I will add some comments to the I'ble itself about the content.