[jacquesm]

To make an image you need two axis, one horizontal, one vertical. Because the earth is already moving if you have a single photodiode looking at the stars you will scan a line if you wait a while. By adding a second axis of motion such as a speaker which you modulate with a saw-tooth curve you can add a second axis. If you then scan over time you can re-constitute the image by plotting the dots with the intensity captured by the diode taking into account the driving voltage of the speaker and the time that has passed.

[rocky1138]

I get that. I guess I was just confused as to why your first thought was to use a speaker to move the photo diode as opposed to an Arduino with a stepper motor.

[monochromatic]

It's an exercise in simplicity. Adding an Arduino is a little against the spirit.

[rocky1138]

Can you explain how a speaker with a square wave would move the diode? I'm so confused.

[jacquesm]

Sawtooth, not a square wave. Hook the speaker up to some kind of frame, glue a small hinge to the cone, hinge to an arm that's anchored relatively close to the speaker, diode at the far end of the arm in a tube so the light is directional, instant scanner :)

[zkms]

Now you're thinking with superresolution!

[jacquesm]

Oh, I just had an even nicer idea that I really will have to try. I won't say what it is yet to not spoil the surprise but I'm sure that it will work :)