SUNSET: 
The Lure of Variable Stars
Studying and recording the ups and downs of variable stars is a pleasant pastime that can also be scientifically rewarding. Here's a simple project to get you going.
The Setting Circles on Your Telescope
Beginners should ignore them and learn to navigate the sky by eyeball instead. However, setting circles do have their uses -- if you make all the right adjustments first.
A Galaxy-Hop in Leo
Even with a modest telescope and a poor sky, you can ferret out many faint, far galactic wonders by using a good map.
How to Care for Your Telescope Optics the Right Way
The mirror in your telescope will probably work fine with a bit of dust on it, but if it's really dirty, you may want to clean it — carefully!
Occultations: The Fastest Things in the Sky
Watch in your telescope as the edge of the Moon snaps a star out of sight.
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…
Star Names: Where Do They Come From and What Do They Mean?
Confused by the bizarre names that astronomers have given the stars? Here's where they come from and what they mean.
Is it true that Andromeda Galaxy is moving toward us?
Is it true that the Andromeda Galaxy is blueshifted and moving toward us? How can this happen in an expanding universe? The Andromeda Galaxy (M31) is indeed approaching us, by about 300 kilometers (190 miles) per second measured with respect to the Sun. If you subtract the Sun’s orbital motion…
Why do photos of lunar or Martian craters sometimes appear inside-out?
Frequently when looking at photos of lunar or Martian landscapes, I see craters as blisters. This can usually be rectified by turning the picture upside down; then craters reveal themselves as indentations rather than bulges. Do I need spectacles? No; this common illusion is all in the brain. Whether you…
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…
What is the most distant human-caused event that’s been easily verifiable with ordinary optics?
Like other amateurs, I observed the brightening of Comet Tempel 1 after it was hit by Deep Impact on July 4, 2005. Was this the most distant human-caused event that’s been easily verifiable with ordinary optics? (I used my 12-inch Dobsonian reflector.) Yes, we think so. The Deep Impact collision…
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…
How do you convert celestial coordinates for equinox 1950.0 to 2000.0?
I use Burnham’s Celestial Handbook, which gives objects’ celestial coordinates for equinox 1950.0. How do I convert these to 2000.0, the current standard? First off, the difference isn’t great. Fifty years of precession change an object’s right ascension and declination by a total of 0.7° at most (if it’s near…
Some Useful Astronomy Terms for Beginners
Take a few minutes to learn the most important astronomy terms.
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…
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…
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).…
Where was the Big Bang located?
The commonest misconception about the Big Bang is that it happened at some particular spot in preexisting empty space.
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.…
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…
