One class of object which you can observe even in badly light-polluted skies are binaries, or double stars (actually multiple stars – most star systems consist of more than one star).
Why observe doubles?
Well, first of all they can be very attractive. The famous double star, Albireo, is a striking combination of a brighter, warm, orange star, and a fainter blueish companion. There are many others.
Secondly, they are a good test of your eyesight, optics, and the seeing conditions. The closer two stars are, or the bigger the difference in brightness, the h
Finally, you can do real science. There are countless thousands of double stars within the reach of amateur equipment. As they orbit around each other, they change position over the years. Some of these stars haven’t been looked at for many years – by checking up on neglected doubles you can submit valuable results.
Here are a few I’ve imaged so far.
|Gamma Andromedae, or Almach, has two main bright components. The brighter is magnitude 2.3, the fainter 5.5. The colours are given as yellow and blue, but in this image it’s hard to make out the secondary as it’s washed out by the brightness of the primary. They are approx 10″ apart.|
|Albireo – beta Cygnii – as mentioned above is a famous double. The primary is magnitude 3.1 and yellow/orange; the secondary is a blueish 5.1. They are 34″ apart.|
|Mesarthim, or gamma Arietis, is a beautiful sight in the telescope. A 4″ refractor splits them easily even at low power; they are almost exactly equal at magnitudes 4.8, and have a seperation of 7.7″.|
|Lambda Arietis is a wide, easy double. The primary is 4.9, secondary 7.9 magnitude. Seperation is 37″. The primary to me was white/orange, the secondary white/blue.|
|Beta Monocerotis is a pretty,triple star, about half-way between the belt of Orion and Sirius. The main component is mag 4.6; B is mag 5.2 @ 7.2″ from A, and C is mag 5.6 @ 2.8″ from B. All looked blue/white to me. (2x barlow)|
|Castor (alpha Geminorum) is an easy double in a 4″ scope. The components are both bright white, magnitudes 2.0 and 2.9. Seperation is 4″. There is a mag 9.5 third star which is obvious visually at 73″, but I didn’t capture it here. (2x barlow)|
|Sigma Orionis is a multiple system just south of Orion’s belt. The primary is the close (100AU) double AB, magnitude 3.8. At 2 c’clock is D at mag 7.2, 13″ from A; top of image is E (7.2, 13″). 10th mag C is visible in the original by the locator lines, but not in this image. (2x barlow)|