25. F6
The G band is slightly stronger than at class F5. Fe I 4045 and
4226 are stronger relative to
H
and
H
.
The ratios of 4077 to
4226 and to the Fe
lines at 4045, 4063,
and 4071 are sensitive criteria of luminosity, Luminosity classes III,
IV, and V, which are separated from one another by about 1 mag., are
distinguishable without ambiguity. Spectroscopic parallaxes of high
accuracy can be determined for the low-luminosity stars of classes
F5-F8.
| Star | MKK | a | | m | HD |
 3 Ori...... | F6 V | 04:44 | +06°47' | 3.3 | F8 |
Pup....... | F6 II | 08:03 | -24 01 | 2.9 | F5 |
 2
UMa.... | F6 IV | 09:01 | +67 32 | 4.9 | F8 |
 UMa...... | F6 III | 09:26 | +52 08 | 3.3 | F8p |
 Boo........ | F6 IV | 13:42 | +17 57 | 4.5 | F5 |
 Vir........ | F6 III | 14:10 | -05 31 | 4.2 | F5 |
| Boo....... | F6 IV | 14:21 | +52 19 | 4.1 | F8 |
|
Ser........ | F6 IV | 15:51 | +15 59 | 3.9 | F5 |
 Dra....... | F6 V | 18:22 | +72 41 | 3.7 | F8 |
 Peg....... | F6 III-IV | 22:41 | +11 40 | 4.3 | F5 |
 |
| High resolution image |
 |
| High resolution image |
