My first Magazine Sky & Telescope - 01.2019

which at Robbins Farm resolves clusters about as well as a 60-mm refractor does under dark skies. An 8- or 10-inch scope would give even more impressive views of almost all the objects. Cassiopeia Tonight we will explore the bottoms of pages 1 and 11 in Sky & Telescope’s Pocket Sky Atlas, starting in Cassiopeia, dipping brieﬂ y into Perseus, and ending in Camelopar- dalis. This is the region where the cluster-rich galactic plane passes farthest north, so it remains high for a very long time for observers at mid-northern latitudes. U.S. observers will ﬁ nd all these objects well-placed in the evening sky from October to early March. The beginning of our tour is extraordinarily easy to navigate because it traces along one of the most promi- nent patterns in the night sky: the W of Cassiopeia. We’ll start with the startlingly red star WZ Cassiopeiae 1.5° northwest of Beta (β) Cas, the westernmost star of the W. The variable-star designation WZ is omitted in the Pocket Sky Atlas, but the star has the label (c) to mark it as a carbon star. It’s also marked as a double, though its companion, about 1′ to the east, is physically unrelated. Carbon stars are red giants with an excess of carbon in their outer regions. The carbon forms molecules that ﬁ lter out almost all the blue light, giving these stars a very distinctive appearance. Normal red giants and supergiants such as Betelgeuse have a reddish tint, like incandescent light bulbs. Carbon stars come in various hues of deep, saturated red, more like Christ- mas-tree lights. In the case of WZ Cas, the color is further enhanced by the contrast with its blue-white companion. Like all carbon stars, WZ is a variable. It’s usually signiﬁ cantly brighter than its companion, but they’re near-twins in brightness when WZ is at the bottom of its cycle. Carbon stars make great targets for bright-sky observers, because skyglow does not reduce the percep- tion of color, and might even enhance it. The Astro- nomical League has an excellent list of carbon stars at https://is.gd/al_carbon_stars . But beware of the magnitudes; many of the stars come nowhere near the bottoms of the ranges listed in that table. Tracing eastward along the W, our next stop is the wonderful double star Eta (η) Cassiopeiae. I can split it with some effort at 30×, but it looks much better at 50× to 90×, with a brilliant yellow-white primary widely separated from the much fainter reddish secondary. Like carbon stars, colorful doubles are ideal bright-sky targets. Sissy Haas’s Double Stars for Small Telescopes is a great resource for double-star fans, as is the online database https://is.gd/haas_project . sk yandtele scope.com • JA N UA RY 2 019 63

My first Magazine Sky & Telescope - 01.2019 | Page 65