6 Rasalgethi (Alpha (_) Herculis)
This is another easy pair to see with small telescopes, although tricky to split at only 4.6 arcseconds’ separation. Rasalgethi is the southernmost star in the eastern leg of Hercules. Find mag. +3.9 Epsilon (¡) Herculis at the southeastern corner of the Keystone of Hercules. Next, proceed 7° southeast to 3.1 magnitude Delta (b) Herculis, the eastern knee. From Delta, move 10.5° south to mag. +3.3 Alpha (_) Herculis.
Moderate to good seeing will be required to split the components and discern their colours. Again, both components are the same spectral class (M5), but they appear to be different colours at the eyepiece. The brighter mag. +3.5 A component appears orange at 62x magnification while the dimmer mag. +5.4 B component appears green or yellowish green at 110x.
Rasalgethi (Alpha (_) Herculis) Magnitudes +3.5 and +5.4 Separation 4.6”