Secchi considers that there is evidence of an actual change in the spectrum of the star, an opinion in which Mr.Huggins does not coincide.

In the telescope Betelgeuse appears as "a rich and brilliant gem," says Lassell, "a rich topaz, in hue and brilliancy differing from any that I have seen." Turn next to [beta] (Rigel), the brightest star below the belt.

This is a very noted double, and will severely test our observer's telescope, if small.

The components are well separated (see Plate 3), compared with many easier doubles; the secondary is also of the seventh magnitude, so that neither as respects closeness nor smallness of the secondary, is Rigel a difficult object.

It is the combination of the two features which makes it a test-object.