SUNSET: 
If you lived on Saturn, would its rings be visible from the equator or the poles?
If I lived on Saturn, would its rings be visible from the equator or the poles? Above the cloudtops and neglecting refraction, geometry dictates that you’d see nothing from the poles. As you moved toward the equator, the bright A ring would start coming into view at latitude 66° (roughly…
Will it ever be possible to observe Halley's Comet around its entire orbit?
With larger and larger telescopes being built, will it ever be possible to observe Halley's Comet around its entire orbit? It's already being done! The most recent observations of Halley were made on March 6, 7, and 8, 2003, by Belgian astronomer Olivier Hainaut and his colleagues, who acquired simultaneous…
What defines a planet's north pole?
Uranus is often said to have a retrograde rotation with its axis tilted 98°. Why don’t we say it has a direct spin with the axis tilted 82°? Since 1982, the International Astronomical Union has defined the north pole of a planet to be the pole that lies north of…
What would happen if I fed animatter into a black hole?
What would happen if I fed animatter into a black hole? Could this be a treatment to get rid of black holes? No. Antimatter has positive mass just like ordinary matter, so the black hole would merely get larger and heavier. Whatever fireworks happened inside the hole, if the anitmatter…
Why do people doing CCD imaging often stack five 1-minute exposures instead of taking just one 5-minute exposure?
Why do people doing CCD imaging often stack, say, five 1-minute exposures instead of taking just one 5-minute exposure? Modern digital cameras capture faint astronomical objects with much shorter exposures than their film-based counterparts did, but it still takes an exposure of many minutes to produce a good picture. So-called…
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…
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…
How can we find the Sun's place among the constellations?
How can I find out how our Sun would look among the constellations, as seen from a nearby star? What made me curious was a painting by space artist David Hardy that pictured the Sun as an extra star in Cassiopeia. Fancy planetarium projectors produce such scenes, but you can…
What determines a moon's atmosphere? (Why is Titan's atmosphere so dense?)
Why is it that Saturn’s moon Titan has a dense atmosphere, yet Jupiter’s Ganymede and Callisto (about the same size as Titan) do not? Blame it on their parent planets. All three moons are a mixture of rocky materials and water ice, and the crystalline structure of ice is particularly…
Why Do Bright Stars Look Bigger?
If stars appear as mere points, as we’re always told, why are some stars big and some small in every image I’ve ever seen? Photography does strange things to stars. In fact, the sky on photographs looks rather different from the sky we see visually (S&T: June 2004, page 128).…
Can you adjust a f/7.7 spherical mirror to act like a f/8.0 parabolidal mirror by racking the focus farther out?
My 114-millimeter (4.5-inch) Newtonian reflector came with an f/7.7 spherical mirror. I can purchase a 114-mm f/8.0 paraboloidal mirror. Can I simply adjust for the 34 mm of added focal length by racking the focuser farther out, or should I extend the main tube? Either way, is the upgrade worth…
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…
Would a large concave mirror suffice for low-power views of extended deep-sky objects?
A large concave mirror, even of low quality, has lots of light-collecting power. Would such a mirror suffice for low-power views of extended deep-sky objects, even if it didn't show stars as neat dots? For example, a 20-inch plastic mirror might be fairly inexpensive. My 7th-grade science teacher once let…
Were stars artistically depicted with diffraction spikes before the invention of the Newtonian reflector?
Were stars artistically depicted with diffraction spikes before the invention of the Newtonian reflector? If so, why? Stars were being drawn with points or spikes long before Isaac Newton announced his reflecting telescope in 1671. Just look at early works of art, flags, ancient coins, and the charts of the…
Why Are There No Green Stars?
There are red stars, orange stars, yellow stars, and blue stars. Why no green stars?
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.…
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…
Would a perfectly reflecting full Moon be just as bright as the Sun?
I've read that the full Moon has a magnitude of about -13 and an albedo of about 3%. That implies that if the lunar disk reflected 100% of sunlight it would appear more than 30 times as bright, or about magnitude -17. But since it has the same angular diameter…
Will asteroid 99942 Apophis eclipse the Moon when it passes by?
When I heard that a 300-meter asteroid will approach Earth at a distance of only 18,000 miles in 2029, I figured it was time to break out the old slide rule. Wouldn't an object that big and close be able to eclipse the Moon, if it should pass in front…
What is the unfamiliar star in Johnny Horne's image of the Horsehead Nebula?
While looking at Johnny Horne's recent image of the Horsehead Nebula (September issue, page 65), I glanced up at my own picture mounted on the wall and suddenly noticed a "star" in Johnny's image that does not exist in this part of the sky. It must be a passing asteroid,…
