To best see faint deep-sky objects like galaxies and nebulae, you have to make sure your eyes are have been conditioned with proper dark adaptation. Here’s what you need to know.
Averted Vision
Averted vision exposes the most sensitive part of your eye and lets you see much fainter objects. If you’ve never tried this before, you’ll be amazed at how much more you can see, with or without a telescope. It takes a little practice, but averted vision is an essential skill for all stargazers.
Stellar Magnitude: Understanding the Brightness of Stars and Planets
Astronomers use a numerical measure called “magnitude” to describe the brightness of stars, planets, and other objects in the night sky. Here’s how it works.
By convention, brighter objects have a smaller numerical value of magnitude than fainter objects. So a star with magnitude 4 is brighter than a star with magnitude 5, for example. It’s a little like a ranking system, where brighter stars are assigned a smaller number. Again, by convention, stellar magnitudes are defined so that an object with magnitude 1.0 is 100 times brighter than an object with magnitude 6.0. So each step of 1.0 in magnitude is the “fifth root” of 100, which is a factor of 2.512. That means a star of magnitude 3.0 is 2.512 times as bright as a star of magnitude 4.0, which is 2.512 times as bright as a star of magnitude 5.0, and so on. Try it yourself, if you have a calculator handy.
Sirius, the Dog Star
A spectacular sight in the cold dark sky of a northern winter, the blue-white star Sirius shines as the brightest star save for the Sun. Its name comes from the ancient Greek seirios, “scorcher”. As the most prominent in Canis Major (the Big Dog), Sirius is often called the “Dog Star”.
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