8.4. SPECTRAL COORDINATE SYSTEM REPRESENTATIONS

85

Non-linear Spectral Algorithm Codes1

Table 8.6.

Code

Regularly sampled in

Expressed as

Frequency

Wavelength

F2W

Apparent radial velocity

F2V

Air wavelength

F2A

Wavelength

Frequency

W2F

Apparent radial velocity

W2V

Air wavelength

W2A

Apparent radial velocity

Frequency

V2F

Wavelength

V2W

Air wavelength

V2A

Air wavelength

Frequency

A2F

Wavelength

A2W

Apparent radial velocity

A2V

Logarithm

Any 4-letter coordinate type

LOG

Detector

Any from Table 8.5

GRI

Detector

Any from Table 8.5

GRA

Not regular

Any 4-letter coordinate type

TAB

1Characters

6 through 8 of the value of the keyword CTYPEi a.

FITS Standard