Big Dipper photo

Astronomy Questions & Answers

How far away are the stars I see through my telescope?

The faintest stars I can see in my 4-inch refractor are 12th magnitude. If one of these stars is just like the Sun, how far away is it? The Sun would be magnitude 12.0 if it were 880 light-years away. That’s not very far in the grand scheme of the…

Astronomy Questions & Answers

What is a Sundog, and How Did "Sundogs" Get Their Name?

Why are "sundogs" called by that name? Before answering the why question, let me answer the what question that comes before: namely, what is a sundog, or mock Sun, in the first place? A sundog is a concentrated patch of sunlight occasionally seen about 22° to the left or right…

Laser beam from Subaru Telescope

Astronomy Questions & Answers

What is the faintest object imaged by ground-based telescopes?

I know that the Hubble Ultra Deep Field imaging campaign reached a limiting magnitude of 31, but what is the faintest object imaged by ground-based telescopes? Furthermore, how is it that an amateur astronomer was able to reach magnitude 24 with a 16-inch telescope, when even Hubble has gone no…

Westerlund 2 as viewed by Hubble's WFC3

Science-based Q&A

What does “true color” mean in a deep-space photograph?

What does “true color” mean in a deep-space photograph? How would a galaxy or nebula actually look to the naked eye from close up? “True color” is how an object would look if you were nearby or were viewing it in a telescope under a dark sky, and if its…

Venus 7 days from inferior conjunction, imaged by Damian Peach.

Hobby-based Q&A

Is it possible to see the crescent of Venus?

Is it possible, with better than normal eyesight, to see the crescent of Venus? That question has been controversial, but in fact some people can. The rough rule of thumb is that someone with excellent vision can just resolve two image elements 60 arcseconds (60") apart. At times, this is…

Hobby-based Q&A

How can I see more colors through my telescope?

Nebulae and galaxies invariably look like shapeless, colorless blobs in my 6-inch telescope, a far cry from their spectacular appearance in photographs. If I buy a 12- or 14-inch scope, will I see a dramatic improvement? Would that it were so! A larger telescope will better reveal the shapes of…

Astronomy Questions & Answers

If you combine the magnitudes of all visible stars, how bright a star will you come up with?

Just wondering. . . . If you combine the magnitudes of all visible stars (down to 6th magnitude), how bright a star will you come up with? About 9,000 stars are brighter than magnitude 6.5, the traditional criterion for naked-eye visibility. Their combined magnitude is almost exactly –5, which is…

Astronomy Questions & Answers

Can you get sharper images by stopping down your scope with a cardboard mask?

Old astronomy books often say you can get sharper images on a night of poor seeing by stopping down your telescope with a cardboard mask so it has a smaller aperture. New books don’t mention this. It this a forgotten secret? In my experience, if stopping down a telescope sharpens…

Hobby-based Q&A

Will meteor showers be enchanced if you fly 3,000 feet above the ground in an airplane?

I recently got my pilot license. Will meteor showers be enhanced at all for my girlfriend and me in a low-winged Tomahawk airplane, flying 3,000 feet above the ground?There are several tradeoffs to consider. True, you’ll be 1 kilometer closer to the meteors overhead. But most of them flash into…

Saturn and Antares

Astronomy Questions & Answers

What was that flashing light in the sky?

I'm new to astronomy (1½ months) and I live in New Jersey. Last night, July 31st, I saw a bright planet (I assume Jupiter) in the southwestern sky, and just below it what looked like an airplane with a flashing red tail marker — but it never moved. When I…

FIsh's Mouth or Dementor?

Astronomy Questions & Answers

Why aren't Earth's night skies more colorful?

Why are Earth's skies so boring? You see pictures of galaxies, nebulae, clusters, etc., but they're always far away. Why couldn't Earth have been in the middle of a colorful nebula or some other non-boring zone of space? Celestial photos show what things would look like if your eyes were…

Moon's skyglow

Astronomy Questions & Answers

How does the Moon's phase affect the skyglow of any given location, and how many days before or after a new Moon is a dark site not compromised?

How does the Moon's phase affect the skyglow of any given location? How many days before or after a new Moon is a dark site not compromised? The answer is complicated because the Moon's glow is even more directional than light pollution. Skyglow is several times brighter near the Moon…

NGC 4889

Astronomy Questions & Answers

What's the most distant object I can see with my telescope?

Is there a more distant object than NGC 4889 (Caldwell 35) that I can see with my 5-inch reflector? Yes, by a factor of 7! Think quasars. NGC 4889 is a member of the Coma Galaxy Cluster, which lies about 300 million light-years away. But the quasar 3C 273 is…

Where to find Pegasus

Astronomy Questions & Answers

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…

M33, the Triangulum Galaxy

Astronomy Questions & Answers

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…

Hobby-based Q&A

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…

Astronomy Questions & Answers

Should I wear eyeglasses while observing?

Should I wear eyeglasses while observing? If you are near-or farsighted, with no other eye problems, definitely take them off. You’ll have to tweak the focus, but you’ll see objects in the telescope just as clearly as if you had 20:20 vision. By taking off your glasses you’ll avoid the…

Hobby-based Q&A

Focal Ratio vs. Aperture: What Makes an Object Look Brighter Through a Telescope?

How can you make a star or deep-sky object, such as galaxies or nebulae, look brighter? The total brightness of a star or other object is determined by the telescope’s aperture, also called light grasp. The focal ratio (also called f/number, that is, the focal length divided by the aperture)…

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