Learning About the Sky

Astronomy for Beginners: How to Get Started in Backyard Astronomy

Astronomy doesn't deserve its reputation as a tough, expensive hobby. You just need to begin with the right advice.

Explore the Night with Bob King

See Comet PanSTARRS (C/2013 X1) in Binoculars at Dawn

An old friend from winter returns for an encore in the morning sky. Already visible in binoculars, Comet PanSTARRS (C/2013 X1) may reach naked-eye visibility in June.

Binocular basics

Explore the Night with Bob King

Watch Andromeda Galaxy Blossom in Binoculars

How much can you see of the Andromeda Galaxy system with just a pair of binoculars? Turns out a lot!


Stargazing Basics

Binoculars for Astronomy: Ultimate Guide to Selecting and Buying

Ordinary binoculars are your ideal "first telescope." And they're so versatile that even seasoned stargazers find them indispensable.

Explore the Night with Bob King

9,096 Stars in the Sky—Is That All?

Ten thousand stars bedazzle the eye on a dark night. Wait, how many?

foam-pad dew shield

DIY: Astronomy Projects & Guidance

Dealing With Dew: Dew Heaters, Dew Shields and More

How to keep your optics dry and clear even on the dampest, dewiest nights.

Roof-prism binoculars

Hobby-based Q&A

Why do the best roof-prism binoculars need a phase-correction coating?

Why do the best roof-prism binoculars need a phase-correction coating? How does it work, and why is it not used in Porro-prism binoculars? A roof prism splits the light cone from an objective lens into two separate pathways, involving different internal reflections, before recombining them into an erect image at…


Hobby-based Q&A

Why do Schmidt-Cassegrain telescopes have focal ratios of f/10?

Why do most if not all of the Schmidt-Cassegrain telescope I see advertised have focal ratios of f/10? During the past 20 years or so, amateurs have favored shorter tubes for both refractors and reflectors, even if it meant paying for more costly optics. Portability is the chief motivation -…

Eyepiece Barrels

Astronomy Questions & Answers

Where did the 1 1/4-inch standard size for eyepiece barrels come from?

Where did the 1 1/4-inch standard size for eyepiece barrels come from?   This barrel size was adopted shortly before 1890 by John A. Brashear in Pittsburgh, Pennsylvania, says Bart Fried of the Antique Telescope Society. Then W. & D. Mogey of Plainfield, New Jersey, and other firms followed suit.…

Mirror Cleaning

Hobby-based Q&A

What should I do if my telescope mirror is dusty?

I took my new scope out last night and pointed a flashlight down the tube. My mirror looks really dusty. What should I do? The answer is simple: Don’t shine a light down the tube at night! Seriously, it only makes the dust look a lot worse than it is.…


Hobby-based Q&A

What's the difference between two Plössl eyepieces?

I bought exactly the same Plössl eyepiece that a buddy has, but mine doesn’t work as well as his. Did I get a lemon? That’s possible, but very unlikely. Our guess is that your telescope has a short focal ratio, perhaps f/5 or less, while your friend may have an…

Mercury near the Sun's limb

Hobby-based Q&A

How can I polar align in the daytime?

I want to see a planetary transit. How can I polar align my telescope in the daytime? One good way is to use the Sun. Carefully level your mount with a bubble level and set the polar axis to the latitude of your site. Hang a weighted string from the…

Hobby-based Q&A

How do I clean eyepiece lenses?

Very carefully — and not often! Here are some tips to help you keep your optics clean.