Unlike the optical spectrum, the X-ray spectrum is quite simple.

Of the Five, she was the only observational astronomer, even though her specialty was not in the optical spectrum.

On the optical spectrum, blue is located between violet and green.

Only a small part of the optical spectrum is visible to the unaided eye.

One is optimized for the blue part of the optical spectrum and one for the red.

Looking at a light source through the prism thus shows the optical spectrum of the source.

Currently, equipment can be tuned over only a small part of the optical spectrum.

Pulses are repeated for repetitive measurements of the optical spectrum.

The nitrogen seen in the optical spectrum remains an enigma.

Two systems of strong emission lines were identified in the optical spectrum of this quasar.