Cr285 — Ursa Major Moving Group

About

Collinder 285 is the Ursa Major group: stars that drift together through space, probably born together, and the nearest such family to the Sun, with a core near 80 light-years from us. Most of the Big Dipper belongs to it, and Richard Proctor first noticed the shared drift in 1869.

Imaging tips

• Dubhe and Alkaid are not members; Alioth, Mizar, Merak, Phecda and Megrez are core stars, so the Dipper itself marks the core.
• The wider stream of members reaches from Cepheus down to Triangulum Australe, so no single frame holds the group: use a wide-angle lens or a mosaic.
• Physically the core spans roughly 30 × 18 light-years, and the group's combined brightness is about magnitude +0.4.
• Broadband is the filter choice.
• Best March and April; it passes nearly overhead, peaking near 84° from 50°N.