Forever I wanted to build a heliostat - a device with a mirror that follows the sun ☀️ and guides the light into 1 spot.

I even started a project 9 years ago https://github.com/saramic/eternal-sunspots to build one and have it controlled by simple javascript program that can be written by kids.

There is also one in Sydney I visited, but here is probably a more informative news report on it

  • One Central Park’s famous heliostat - The Sydney Morning Herald and The Age

    One Central Park's famous heliostat - The Sydney Morning Herald and The Age

Recenty one of my sons built a make shift pin hole camera where he was intruigued at the dimmer, and yet focused view of his LED light. He was asking for some tracing paper to act as a sort of display. This got me thinking about a bunch of other related experiments like diffraction gratings, making spectroscopes fromm DVDs (acting as the diffraction grating) and visual acuity, experiments around when a display is a “retina display”.

so taking to the web I found a bunch of resources and tools we could get to explore further.

Spectroscope

A bunch of simple videos out there for kids to build one using an old DVD/CD

What most of these seem to miss is lining the inside with black paper (assuming that is an option, which it is in my case) or even painting it witll matt black paint, like say chalk board paint. Finally I was hoping that one of these would put a ruler in there or some guide so you could hope to “compare” what is viewed. It does feel most of these are driven at “just create a rainbow” for your kids as opposed to be able to see spectral lines in a sodium or mercury street lamp, or when buring a salt in a flame? I suppose it may be time to build and experiment.

Which reminds me the first time I saw this idea was in one of the O’Reilly books on forensics, Illustrated Guide to Home Forensic Science Experiments by Robert Bruce Thompson, Barbara Fritchman Thompson,

where it was used to identify materials that may be contained in soil samples by burning them, elements like: Aluminium, Barium, Iron, Mercury, Sodium and Strontium.

The device used there was

Whilst on the topic of makezine this idea of “listening to light” also got dragged up with some simple circuits described to pass sound over light https://makezine.com/projects/amateur-scientist-listening-to-light/

Pinhole cameras

Diffraction grating experiments

https://www.physics.purdue.edu/irnanodev/docs/outreach/Diffraction%20grating%20experiments.pdf

Some hardware

Or maybe at some stage a full on Optilcal experimenters kit like:

OR maybe that is the point, to end up with an “optical experimenters” setup

at some stage the idea would be to also be able to move a mirror or light in a controlled manner. It sounds like precision “piezo motor stages” like pi-usa.us are the way to go.

visual acuity

The angular resolution of the human eye typically ranges between 40 arcseconds and 1 arcminute. To perceive two separate points, at least three photoreceptors arranged in a row are required: one to receive light from each of the points, and one for the gap in between the points. For an angular resolution of 1 arcminute (which corresponds to 0.3 m at a distance of 1 km), the images on the retina are separated by approximately 6 μm, meaning the centre-to-centre distance between two neighbouring receptors is 3 μm. At an angular resolution of 40 arcseconds, the distance between the imaged points is approximately 4 μm.