Summer Double Stars
June 1997 :
The same hazy summer skies that provide excellent views of the planets also bring many double stars within reach of the small-scope user, some of which are close pairs. Here are just a few of these stars, waiting to be observed before the Square of Pegasus rises to announce that fall is but three months away.
? (beta) Sco
A lovely double at any powerin its residence in northwestern Scorpius; its components are 15 arcseconds apart and sparkle beautifully at 80x and 120x. The magnitude 3 brighter star is diamond white, its fainter companion is white with a blue-green tint.
? (nu) Sco
2 degrees due east of beta Scorpii, and a great quadruple system to examine under very high power on nights of excellent seeing. At low power, nu looks like a wide pair of stars, mags 4.5 and 6.5. At 150x, the mag 6.5 star resolves into two stars of mags 7 and 7.8 separated by 2.3 arcseconds. At 375x, the mag 4.5 star resolves into a psir of mag 4.5 and 6.5 stars only 1.2 arcseconds apart. They all look yellow to me, despite their spectral class of type B; what colors do other observers see?
? (eta) CrB
This naked-eye pale yellow star in the western part of the Northern Crown will resolve into twin mag 5 stars 1 arcsecond apart at 375x if the seeing is excellent. I have looked at this star on many nights and have split it only 3 times; save it for really good seeing! These late June nights there is a lovely mag 6.5 orange star a couple degrees to eta's north which I think may be the long period variable S Coronae Borealis near its maximum.
? (alpha) Her
Ever notice that this star seems almost as bright as the alpha star marking the apex of Ophiuchus, and at other times it is distinctly fainter? Not only is alpha Herculis a semi-regular variable whose magnitude range is 3.1 to 3.9, its also a spectacular double star. The orange primary mag 3 star is attended by a blue-green mag 5.5 companion 4.5 arcseconds away. There are stunning at 120x.
70 Oph
A beautiful double in the eastern shoulder of its constellation, part of the old asterism known as Poniatowski's Bull, notable for its colors of gold and red-orange. An extensive write-up of thes star is in Burnham's Celestial Handbook.
Antares
Has anyone ever seen this double star? Some observing guides state that it is resolveable with a 6-inch scope, but I've never managed to do it with my 6-incher. Its companion is supposed to appear green. I am going to try it with the Clark at the club.
? (beta) Cyg
Albireo, famous for its lovely orange and blue colors. A few years ago Sky & Telescope reported that Albireo is an optical double, not a true gravitationally bound system. I have never seen this star look lovelier than it did in Jim Hendrickson's Tele Vue Pronto scope at the June Skyscraper meeting. I'm looking forward to seeing omicron-1 Cygni's gold and blue colors through it soon!
