What is a spectrograph?

It is an instrument for producing and photographing a spectrum. Used to measure properties of light over a specific portion of the electromagnetic spectrum.

What is an altimeter?

It is a dialled meter for showing how high an aircraft or spacecraft is above ground. Most altimeters work using air pressure. The measurement of altitude is called altimetry

What is a telemeter?

It is a piece, or pieces, of apparatus for measuring physical changes from a distance. It has wide application in space technology.