Celestia Forums

The entry for Dubhe in the star info that comes with 1.3.2 has a bad classification. It says F7V but Dubhe is actually in the KIII range.

It's listed with a composite spectrum of F7V in the Hipparcos catalogue, which is how it comes to be listed as such in Celestia - presumably the Hip classification is influenced by its F-type companions.

Grant

Celestia uses the Hipparcos catalog (plus corrections)

In field H76, the Hipparcos catalog claims HIP 54061 is classified as "F7v comp" and field F77 contains a "G" meaning the spectral classification was updated after the release of the Hipparcos Input Catalog.

Simbad says it's a spectroscopic binary and classifies it as "K0 Iab"

According to http://domeofthesky.com/clicks/dubhe.html
the spectroscopic companion has an F0v classification, which might explain the "comp" comment, but also mentions Dubhe C, 280 arc seconds away, with a classification of F8.

This makes me wonder if whoever updated the Hipparcos catalog confused the two stars.

A similar problem seems to have occurred with Epsilon Bootis, the spectral type information has been taken from the dimmer star in the system.