The Orbit of the Spectroscopic Binary HD 170523

Radial velocities have been measured from twenty-four new spectrograms of the giant B-type star δ2 Telescopii. The orbit has been derived by combining these with eleven observations made in Chile during 1908–17 and three in South Africa during 1952. The mean velocity of the system is –7.6 km/sec and the velocity amplitude of the primary is 34.9 km/sec, with a minimum semi-major. axis of $10.2\,\times\,{10}^{6}\,\text{km}$. The period is 21d.70564, eccentricity 0.218 and mass-function 0.0891 solar masses.