Day 15: One of the things you own but never use

This is a device that you aim at a light source and it displays a spectrum.
It is calibrated in wavelength. It can be used with stars (through a telescope)
to determine their composition. It also can be aimed at a lamp or candle.

It was a very nice gift from my wife Eleanor. I tried it out on various lights
around the house and said I'd use it with my telescope at the next opportunity.
For some reason the "next opportunity" never came.

After this photo I placed it in plain sight so I would not forget it again.