Mu Cephei — Star in Cepheus

Mu Cephei, the Garnet Star, is one of the largest and reddest stars visible to the naked eye — a red supergiant of spectral class M2 Ia about 2,800 light-years away. Its diameter is roughly 1,000 times the Sun's; if placed at the centre of the Solar System its surface would extend past the orbit of Jupiter. The visual magnitude is normally around 4.08, varying irregularly between 3.7 and 5.0 over months to years.

The colour is the attraction. Even in binoculars Mu Cep shows a deep, smouldering red unlike any nearby star. Compare it side-by-side with cooler-coloured Alpha or Alderamin in the same field — the contrast is striking. Located in the southern part of Cepheus inside the IC 1396 nebula complex, which a UHC filter can hint at on dark nights.

William Herschel coined the name "Garnet Star" in 1783 — a simple description of the colour as he saw it through his reflectors. He called it "a most beautiful object… a very fine deep garnet colour, such as the periodical star ο Ceti." The name has stuck for nearly 250 years.