Hobby-based Q&A

Browse the stargazing questions and answers below to delve into the hobby of astronomy. Learn about different types of equipment and what they can do, and discover the limits (read: challenges) of observing the night sky with instruments and the unaided eye.

The Q&As presented here cover a wide range of questions posed over the years by our readers, and we’ve responded with detailed and well-researched answers. What’s the difference between a 6-inch and a 12-inch scope? Can we see the shadows of Saturn’s moons as we can Jupiter’s? And how can you turn your stargazing hobby into an astronomy career? Read on to learn the answers, and if there’s a question that hasn’t been asked, ask it yourself by sending a note to info@skyandtelescope.com.

Parallax

Should you use light-years or parsecs for astronomical distance?

You give astronomical distances beyond the solar system in light-years, but professional astronomy papers use parsecs. Which is preferable? Light-years, no question! Here’s how I see it. The parsec (which equals 3.26 light-years) is defined as the distance at which a star will show an annual parallax of one arcsecond. This means it is based…

How is the date of Easter determined?

How is the date of Easter determined? The rule most people remember is that Easter falls on the first Sunday after the first full Moon following the March equinox. In practice, Roman Catholic and Protestant churches follow a method of calculation adopted with the Gregorian calendar reform of 1582. The ecclesiastical dates of the March…

How can I spot satellite triads?

While binocular observing from Northern California on August 19, 2004, at 6:33 Universal Time, I picked up a trio of satellites moving from the northwest to overhead and passing through Cygnus. I’m sure they were satellites, as all three turned reddish at the same time before disappearing into Earth’s shadow. They seemed to be in…

Tony Flanders's biggest and smallest telescopes.

Will I save money by making my own telescopes?

If I make my own telescope, will I save money? That depends on two things: how large a telescope you’re considering, and how many of the pieces you plan to build versus buy. Given the low prices of today’s commercial telescopes, you will be hard pressed to save money building a 6-inch reflector unless you’re…

How many daylight hours do you get in a year?

No matter where in the world you live, do you get the same number of daylight hours over the course of a year? No. The equator actually gets fewer hours of daylight than most other latitudes. Any given place would be in daylight exactly 50 percent of a year’s time if Earth moved in a…

Where to find Pegasus

What’s my naked-eye magnitude limit?

How can I find out my naked-eye magnitude limit? Count stars inside the Great Square of Pegasus, which is well placed on November evenings. If you can see only two stars within the square, you are reaching visual magnitude 4.6 and your skies are probably light polluted. If you spot eight stars you are hitting…

M33, the Triangulum Galaxy

Can telescopes increase an object’s surface brightness?

I normally can’t see the Triangulum Galaxy (M33) with the naked eye, but it’s easy in a rich-field telescope. So how can you claim (June issue, page 128) that a telescope never increases an object’s surface brightness? The explanation has nothing to do with optics and everything to do with human vision. The telescope does…

sigma 3053

Where can I find double star SAO numbers for my Go To telescope?

I want to observe double stars, but my Go To telescope needs their SAO numbers. Where can I get them? SAO numbers come from the Smithsonian Astrophysical Observatory Star Catalog (1966). They aren’t normally used by double-star enthusiasts, who prefer special notations such as ADS 1630, S748, and Krueger 60.Finding equivalent catalog designations can be…

Could you see astronauts on the Moon?

If there were astronauts on the Moon, could we see them? I get some variant of this question almost every time I show someone his or her first view of the Moon through a telescope, especially at high magnification. The breathtaking sight of lunar craters, mountains, and other features down to the limit of perception…

How do you pronounce “Vega” and “Canis Major”?

How do you pronounce “Vega”? “Canis Major”? In 1941 the American Astronomical Society formed a committee of Samuel G. Barton, George A. Davis Jr., and Daniel J. McHugh to consult with astronomers, educators, Arabic scholars, and planetarium lecturers and come up with a list of preferred pronunciations for common star names and constellations. Their final…