The pair of stars in Albireo is 34 arc seconds apart. What size telescope can resolve them?

Question

The pair of stars in Albireo is 34 arc seconds apart. What size telescope can resolve them? I am thinking it is 34 cm

Answer 1

The smallest resolvable angle, in arc-seconds, in visible light is given by the formula:
116/D
where D is the aperture (diameter) in mm

116/x = 34"
x = 0.24 mm

A 34 cm telescope should be able to resolve angles of
116/340 = 0.34" but Earth's atmosphere limits us to 0.5" on good days.

---

I've looked at Albireo in a 80-mm telescope and it was well separated.

In theory, we should be able to split it with the naked eye (7 mm) but the stars may be a little too faint to be interpreted as two separate dots (the brain has a habit of 'correcting' what the eyes pick up).

Answer 2

You mean 34 cm focal length? Probably. You'd want decent quality, though.