Star Struck

You Can’t See That From Here

Take a look at this beautiful time lapse video of the night sky.

Ah, if only we could find nice dark skies, we could see such sights ourselves, right?  Well, no.  Actually, you would need to travel to Australia (where this video was shot) or some other place equally far south of the equator.  The sky we see from the Northern Hemisphere is not the same sky that our Southern Hemisphere friends see.

Imagine an astronaut, properly space suited of course, floating free in space between the planets, so far from Earth that it is just a bright point in an infinitely black sky.  She can see stars in every direction because there is nothing to impede her 360 degree view.

Standing on the surface of the Earth has its advantages—no space suit is needed for starters.  But that 8,000-mile thick ball of rock does block the view a bit.  It’s so big that it looks pretty flat to us, so it’s sort of like standing on a big table, one that is definitely not transparent.  We’re not going to see anything that is under the table, that is in the direction of our feet.

The way that table is oriented to the sky depends on where we are on the Earth’s surface.

Put that “table” at a different spot, and we see a different part of the sky.

Why does it only matter how far north or south we are, and not how far east or west?  The Earth rotates from east to west, and will bring sections of the sky that are out of our view to the east into sight as it spins on its north-south axis.  Only at the equator itself can you see all of the sky, both the northern and the southern halves.  The north celestial pole, very near the North Star Polaris, would be on your northern horizon and the south celestial pole on your southern horizon.  If you move farther south, Polaris slips below your horizon and will stay there unless you move back in a northerly direction.

Most of the Earth’s land mass and consequently its population lie north of the equator.  But many (I only barely refrained from saying most) of the sky’s most spectacular sights are in the southern celestial hemisphere, visible only by traveling south.

Let’s take a guided tour of that video at the top of the page again.  Our Milky Way Galaxy surrounds us in a belt of stars that we can see from any point on Earth.  But its central region, rich with star clusters and nebulae, is lost in murk near the horizon from most of the northern hemisphere.  From the southern part of the Earth, it is often high overhead.  That is what you are seeing in the first few seconds of the video—our glorious galaxy showing its most star-packed neighborhoods.  Starting at about 0:45, two fuzzy patches appear that start out to the right of the Milky Way’s band.  These are the Large and Small Magellanic Clouds (LMC and SMC), so named because Magellan was the first European to see them on his globe-girdling voyage.  They are companion galaxies to our own Milky Way, much smaller than our home galaxy, about 160,000 light years away for the LMC and 200,000 light years away for the SMC.

See those dark bands that seem to denote an absence of stars in some parts of the Milky Way?  That is not an absence of stars—it is the presence of obscuring gas and dust which is concentrated in the plane of the Milky Way.  It is the raw material out of which stars and planets form, and of which you and I are made.

In the sequence that starts around 2:15, you should see a familiar constellation at the left.  Don’t recognize Orion (three stars in a line for its “belt”; four stars in a rough rectangle surrounding them) when it is upside down?  Australians might dispute who in fact has the right perspective on Orion.

Travel is a wonderful experience in and of itself.  When you have new things to see above you as well as around you, it is even better!

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Printable Star Charts

For those of you found the star charts in the previous post to be useful, you may want something you can print out without draining all the black ink or toner you have. These are the same star maps, but in a different format that has more white space than black. Each of them is set at 10 pm Eastern Standard Time on the 15th of the month, and the views are those seen from Lynchburg.

The first two are for January, first looking south and then looking north.2014 January South Chart

2014 January North ChartAnd these two are for February, first looking south and then looking north.2014 February South Chart

2014 February North ChartEnjoy!

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2014 Sky Watcher’s Guide

You know all those New Year resolutions that you have already broken? I fully intended to post this at least a week ago. Ah well, better late than never…

This post is intended to introduce people to the habit of skywatching, and once the habit is ingrained, to be sure that you will never walk outside, day or night, without at least a glance over your head. Not a bad habit to gain.  Each month throughout the year (there go those resolutions again!) I intend to post a similar update for your information, and repost the background information as well. Since I am so late in the month of January, I am posting information here for February, too.  I haven’t assumed any optical aid beyond a good pair of binoculars. There is plenty to see even without them.


Moon Phases: Full moon nights are good mostly for reading—outside by the light of the moon, or inside with a good reading lamp. They aren’t much good for sky gazing since the brightness of the moon pretty much overwhelms everything else in the sky. Nights with a new moon are dark, and that allows you to see dimmer objects that might otherwise escape your notice. Between the new and full phases, the moon waxes as more and more of its visible surface is illuminated, and it rises ever later. When it is full, it rises at sunset and sets at sunrise, visible all night long. Between the full and the new phases, it wanes, and if you confine your sky gazing to the early evening before midnight, it may not rise until well after you are done.

But the moon itself is a fascinating object, the closest and most easily observed extraterrestrial object. It especially comes into sharper view with binoculars. Look at the moon when it is less than half illuminated, and look along the line separating the illuminated surface from the dark. There the Sun is low in the lunar sky and casts long shadows that throw the deep craters and the tall mountains into higher relief. See if you can spot a bright central peak poking into the sunshine from the dark floor of a deep crater. The best online lunar map I have found is here.

Planets: I’ve confined myself to the five planets that are visible to the naked eye: Mercury, Venus, Mars, Jupiter, and Saturn. For views of Earth, look down.

Meteor Showers: I haven’t tried to include every single one of these, only the ones that might be worth your while to stay up for. The moon phase greatly affects how many meteors you will see; the ideal situation is when a shower occurs during a new moon. The radiant is the point from which the meteors appear to originate; the showers are named for the constellation in which the radiant appears. This is an optical illusion in the same way that railroad tracks appear to meet in the distance; the meteors actually follow parallel paths as illustrated below:

Deep Sky: There are only a few objects beyond the solar system that are visible to the naked eye (other than stars, of course). Even there you need a pretty dark sky. Binoculars will help, and I’ve included some of the more easily spotted objects.

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Posted in Sky Phenomena

Stars of the First Magnitude

No, we aren’t talking about Tom Hanks or Meryl Streep. These are the stars you see in the sky at night. If you have ever been confused by statements like the following, then let’s see if we can help you out.

  • “On 29 November 2013, the coma dimmed to an apparent magnitude of 5. By the end of 30 November 2013, the coma had further faded to below naked-eye visibility at magnitude 7.” (from the Wikipedia article about Comet ISON)
  • “As it is configured now, the ISS has an apparent brightness, or “magnitude,” of around -3 (lower numbers denote brighter objects on this scale), said Joe Rao,’s nightsky columnist.”

As with so many conventions of math and science, it all goes back to the Greeks. Among the many achievements of Hipparchos, one of the greatest astronomers of antiquity, was the creation of the stellar magnitude scale. He assigned a value of 1 to the twenty brightest stars (stars of the first magnitude), all the way down to stars that were barely visible to the naked eye, to which he gave a value of magnitude 6. A modified version of this system is still in use.

Telescopes have extended our vision to encompass objects too dim for naked eye observation. For example, the star known as Kepler 62, with five known planets in orbit around it, has a magnitude of 13.75. What about objects brighter than the brightest star, such as Venus? The only other direction to go from 1 is to zero, and from there to negative numbers. The magnitude of Venus (it varies as its phase and distance from us changes) can be as bright as -4.6. The sun’s magnitude is -26.7.

That’s the quick and dirty. Now for the details—and the complications.

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Posted in Sky Phenomena, Stars

Shopping for a Telescope?

When you are an “astronomy guy”, around this time of year you get inquiries from friends looking to buy a telescope as a Christmas present. Often this is for a child or a grandchild, but sometimes the friend is shopping for him or herself. I must admit to skepticism when someone is willing to spend $1000 on a telescope for their four year old—just exactly who is this telescope for? :-)  But my role is not to judge, just to provide information and to make recommendations.

I want to make it clear that these recommendations are based on my personal experience from childhood until now. My first telescope (at age 10) was an inexpensive reflector from the Sears Roebuck catalog, and my current instrument is a top-of-the-line refractor. I see a lot more with my current scope than I did more than fifty years ago—I know a lot more, too—but I’m not sure I derive any more pleasure from its use. A different astronomy person would probably give you a different list. What that reflects is the wonderful range of options available today. When I built my own telescope in the late 1970s, it was better than anything I could have bought ready-made at the same price. In my opinion you are better served today buying that ready-made scope unless you are skilled in a number of areas beyond being able to use a tape measure, an electric drill and a screwdriver. That’s about all that was required for me in 1979!


DO NOT, REPEAT, DO NOT buy anything from a store that does not specialize in telescopes. What you get there is cheap plastic junk. There are wonderful showrooms scattered around the country, but most people probably do not want to drive that far. The good news is that two vendors (Astronomics and Orion Telescopes) I have used extensively both have wide selections online and excellent customer service. These are certainly not the only vendors available! If you want to get an idea of what is out there, just pick up the latest issue of Sky & Telescope at your local newsstand. These are simply the ones with which I am most familiar.

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Posted in Observatory and Telescopes

Will It Be a Spectacle Or a Speck?

Spectacle or speck?

OK, I stole that phrase. But it’s just too good not to use.

Comet ISON will very soon be upon us. The image above was taken with the Hubble Space Telescope when ISON was a little over four times as far away from the sun as is the earth. Starting in mid-November, it will get ever lower in the eastern sky just before dawn. If it survives its passage very near the sun, we could see it again in early December. But will it be the “comet of the century” promised earlier this year? Or will it join the infamous Comet Kohoutek and numerous other over-hyped comets as a disappointment for the general public? At this point no one really knows, although prospects for the former are—ahem—fading.

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Posted in Sky Phenomena

What “Gravity” Gets Wrong

Let’s establish a few things at the very beginning. I love movies about space. I quite happily go along with improbabilities like warp drives, phasers, Vulcan mind melds and the concept that every extraterrestrial species we encounter will be remarkably humanoid. My very favorite science fiction trope is time travel, as unlikely a physical concept as there is. So I most certainly enjoyed the recent movie Gravity, starring Sandra Bullock and George Clooney, and I would recommend it to anyone as a gripping story and spectacular visual feast. Still, there was this quietly persistent voice in the back of my head sputtering “But, but…you can’t do that!” Will these sorts of things keep you from enjoying the movie? Well, they didn’t keep me from enjoying it, and I am probably the biggest science nerd that most of you know. Without giving away anything that isn’t in the trailer, I’m going to focus on the most egregious of these scientific boo-boos.

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Posted in human spaceflight, Spacecraft

How to Point a Telescope

It was a lot simpler in Galileo’s day.

Up and down, left and right, manually controlled—simple, right? Yes, but simpler was not always better, at least until computers came along. But we’re getting ahead of ourselves.

There are two issues to be dealt with here.

  1. Pointing the telescope accurately.
  2. Following the apparent movement of celestial objects so that they remain in view.

Accurate pointing–The first is not a big problem if you are not working with a high-magnification view. A pair of 7 x 50 binoculars which magnify 7 times (the 50 is the diameter of the light-gathering lens in millimeters) can be hand-held and pointed with relative ease. A typical field of view for these binoculars is 7 degrees, and this is 14 times the width of the full moon.

A larger instrument clearly cannot be hand-held, and larger light-gathering elements (whether a lens or a mirror) allow higher magnifications. Here is the view afforded by a medium-power eyepiece in combination with the 20-inch Gilbert telescope at Lynchburg College’s Belk Observatory. This field is about ¼ of a degree across and is indicated by the red circle beside the moon.

FOV for Gilbert

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Posted in Observatory and Telescopes

Ladies and Gentlemen…Voyager Has Left the Solar System!

To boldly go where no one has gone before…

Bigger than Elvis? I would say so.

NASA announced today that the Voyager 1 spacecraft launched 36 years ago has finally entered interstellar space, the space between the stars. This is an epic stage of human exploration. You can read more about it here.

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Full Moons: Not So Super?

A friend: “Hey, did you see that blue moon last night?”
Me: “Uh, yeah, I went outside and took a peek.” (Even if I didn’t.)

Look, don’t misunderstand. I’m all for anything that gets people outside and looking at the sky, and if overblown media stories about “super” moons and “blue” moons accomplish that, then it’s a good thing. But let me explain why I don’t get all that excited about it.

  • Full moons are right up there with clouds as enemies of astronomical observing. Not only are they so bright that they wash out anything but the brightest stars and planets, they really aren’t much good for lunar observing, either. With the sun directly over the middle of the lunar disk, there are no shadows, and therefore no relief. Compare these two images of the lunar crater Hipparchus, which is near the center of the moon as we view it from Earth. This first one is taken when the moon is nearly full, almost completely illuminated.

Hipparchus at full phase

Now look at this image taken near first quarter, when we see the lunar disk as half-illuminated, with the sun casting long shadows over Hipparchus (which is the central crater). I’ve rotated this image to give it roughly the same orientation as the first one. Look at how much more detail is visible. Can you even tell you are looking at the same object?

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Posted in Sky Phenomena, The Moon