This page will cover a heliostat array prototype. What makes this array interesting is the fact that it uses just two stepper motors to control three mirrors. The idea is to help reduce the overall cost of the heliostat.
There is a downside to connecting the heliostats together like this though. For one, your targets all have to be an equal distance away from the mirrors if you want to concentrate the reflected light into one spot. The light is concentrated by angling the mirrors to create a focal point, and that point is the only spot you can place the target and still have all the light focused. Although it is possible to change the target’s distance, you will have to re-angle the mirrors to do it.
There is also the added complexity of connecting the mirrors together. This isn’t a huge issue, but it does add to the time it takes to figure out how put it together.
Video
Here is a video of the heliostat array in action.
You can’t really see it in the video, but the reflection from the mirror on the left actually drifts high enough that it almost misses the target completely. It takes most of the day for it to drift that far though, so it’s not a complete loss. Some of it is also caused by the fact that I didn’t quite have the settings worked out in the Sun Tracker program when I took the video. This is why the reflection is drifting to the left. I’ve since fixed that much at least.
Pictures
Here are some miscellaneous pictures of the heliostat array.
![DSCI0255 [][4]](http://www.cerebralmeltdown.com/wp-content/uploads/2011/01/DSCI0255-4_thumb.jpg "DSCI0255 [][4]")
![DSCI0250 [][4]](http://www.cerebralmeltdown.com/wp-content/uploads/2011/01/DSCI0250-4_thumb.jpg "DSCI0250 [][4]")
![DSCI0256 [][4]](http://www.cerebralmeltdown.com/wp-content/uploads/2011/01/DSCI0256-4_thumb.jpg "DSCI0256 [][4]")
![dsci0207p[4]](http://www.cerebralmeltdown.com/wp-content/uploads/2011/01/dsci0207p4_thumb.jpg "dsci0207p[4]")
![DSCI0261 [][4]](http://www.cerebralmeltdown.com/wp-content/uploads/2011/01/DSCI0261-4_thumb.jpg "DSCI0261 [][4]")
Here’s one final picture where you can see what happens when the mirrors miss their focal point. The blue circle is where the light from the three mirrors is concentrated on the target. The three red dots in the background show where the light ends up if the target is farther away. If I wanted to move the target back to where the trees are, I would have to re-angle the mirrors.
![img50[4]](http://www.cerebralmeltdown.com/wp-content/uploads/2011/01/img504_thumb.jpg "img50[4]")
Sketchup Model
Apologies for not making comments on all the pictures. Once I have the perfect heliostat design finished, you can be sure that I will document the heck out of it. For now though, it’s better that I use my time to work towards that end.
I do have a Sketchup model though if you want to get a better look at how everything goes together. Its dimensions are pretty much exactly the same as the real version.
Hi,
Me and my brother were looking into modifying a telescope mount tracking system to control a heliostat array. Have you tried this? Is this worth a try or is it fraught with problems? Meade autostar do a cheap budget scope but was thinking of dawn dusk problems, loads, wind etc…
Best regards
Tim Doyle , England
Hi Tim,
I’ve never tried it myself, but I think it could be made to work for one of their “altazimuth” type mounts. I don’t know what changes would need to be made though since I have never seen the inside of one. If these telescopes use stepper motors to pan and tilt, then it would probably be fairly easy to apply the Arduino heliostat program. If they use some other type of electronic trickery to move to a specified altitude and azimuth though, it could be a serious pain.
Of course, if there was an easy way to just feed the altitude and azimuth calculations for aligning the heliostat into Meade’s software , then you might not even have to open the thing up!
I guess, I don’t know enough about the telescopes to be able to determine how much effort it would take to modify one. I’m sure that it is possible though. It just might take quite a bit of experimenting to figure it all out.