Optical versus Physical Doubles

A double star consists of two (or more) suns that appear close together in the sky when viewed with the unaided eye, binoculars or, especially, telescopes. Most of these are true physical systems in relative proximity to each other and bound by their mutual gravitational attraction. However, a small percentage are simply chance alignments of two objects along our line of sight. These are known as optical doubles. In the early days of telescopic astronomy, all double stars were considered to be...

The Joys of Seeing Double

Double stars are the tinted jewels and waltzing couples of the sky. Their amazing profusion, and seemingly infinite variety of color, brightness, separation and component configuration, make them fascinating as both objects of study and Figure 1.1. Albireo (p Cygni), one of the most spectacular visual double stars in the heavens, as imaged by Austrian observer Johannes Schedler using a digital camera on an 1 1-inch Schmidt-Cassegrain telescope. The original 30-second color exposure shows the...

Reporting and Sharing Observations

While observing double and multiple stars can be a rewarding activity on a strictly personal basis and can be enjoyed alone, it is in sharing your observations with other people and organizations that its pursuit realizes its full value. As the old English proverb states, A joy that's shared is a joy made double. At its simplest level, letting family, friends, neighbors, beginning stargazers - and even total strangers passing by - see wonders like the magnificent pair Albireo through your...

Constellation Names and Abbreviations

The following table gives the standard International Astronomical Union (IAU) three-letter abbreviations for the 88 officially recognized constellations, together with both their full names and genitive (possessive) cases, and order of size in terms of number of square degrees. Those in bold type are represented in the double star lists in Chapter 7 and Appendix 3. Constellation Names and Abbreviations Constellation Names and Abbreviations (continued) Constellation Names and Abbreviations...

Pleasure versus Serious Observing

Rampant in the field of amateur astronomy today is a belief that you must be doing serious work of value to science, preferably with sophisticated (and, therefore, expensive) telescopes and accessories, in order to call yourself an observer. This is truly unfortunate, for it has undoubtedly discouraged many budding stargazers from pursuing astronomy as a pastime. The root of the word amateur is the Latin word amare - which means to love - or more precisely, from amator, which means one who...

Star Testing and Collimation

For casual observation of double stars, even a telescope of mediocre optical quality can provide acceptable views, but for more demanding work, such as resolving close pairs or making micrometer measurements,high optical quality is a must. The condition of a telescope's optics and their all-important optical alignment can readily be determined by a simple test using a star itself. Known as the extrafocal image test,this involves looking at the image of a star, both inside and outside of focus...