| Answer | Crossword Clue |
|---|---|
| SPECTROSCOPICAL | Pertaining to an instrument used to disperse light beams. |
| coelostat | an astronomical instrument used to reflect light on to a telescope |
| coelostats | COELOSTAT, an astronomical instrument used to reflect light on to a telescope |
| fugitometer | an instrument used for measuring the fastness to light of dyed materials |
| fugitometers | FUGITOMETER, an instrument used for measuring the fastness to light of dyed materials |
| photomultiplier | An instrument containing a photoelectric cell and a series of electrodes, used to detect and amplify the light from very faint sources |
