6 Rasal­gethi (Al­pha (_) Her­culis)

Sky at Night Magazine - - OBSERVING -

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”

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