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April Skywatch

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I’ve promised a column on some telescope basics, and as the evenings start to warm up it’s finally time to deliver. Maybe you’re interested in more stargazing than casual naked-eye observations from your back porch, but you’re unsure of where to begin. Sometimes the options for purchasing a good starter telescope seem quite daunting. Where to begin? What type should I get? Which mounting is best? How do I avoid a cheap dud?

This month, I’ll offer a few pointers on choosing and getting started using a telescope for some basic backyard observations. As I’ve mentioned before, I focus on observing objects that you don’t need to be in perfectly dark skies to see. My own stargazing takes place in the city limits of Kankakee, with streetlights, trees, and the occasional porchlight marring the view. With a little knowledge and patience though, even a city sky can be a treasure trove.

Of course, it all starts with a good telescope. When I was preparing to purchase a new set of telescopes for my astronomy labs at Olivet several years ago, I asked the members of the Kankakee Area Stargazers for advice. I wanted instruments that were high quality but relatively inexpensive, easy to use and train students to use, and resilient enough that I wouldn’t worry about them being easily damaged The scope most recommended was a basic 6-inch Dobsonian reflector from Orion Telescopes. I purchased a small fleet of these instruments for student use and have had no regrets. They are simple, durable, and offer great viewing.

So what exactly is a 6-inch Dobsonian reflecting telescope? We’ll start with “reflecting.” Telescopes come in two basic types: reflectors, which use mirrors to gather light, and refractors, which use lenses. If you walked into Wal-Mart for a cheap telescope, you’d almost certainly be buying a refractor. Though there certainly are many refractors that are very high quality, you’re not going to get one like that at Wal-Mart. For a real quality refracting telescope, you would be spending several times more than you would for a reflecting telescope of similar size. If you’re looking for a serious but affordable starting instrument, stay away from refractors and start with a good reflector.

The next question is regarding aperture or (in simple terms) size. Generally speaking, the larger the diameter of a telescope, the better view you’ll have of objects. But also generally speaking, larger aperture also means larger price. Six inches offers enough light-gathering power to easily showcase Saturn’s rings or the moons Jupiter, hone in on the Moon’s craters, or (in dark skies) reveal distant nebulae and galaxies.

Next, you need to consider how the telescope is mounted. As it turns out, pointing and holding the telescope steady is one of the most important parts of getting good views (and not getting incredibly frustrated). There are lots of different ways to mount a telescope, but the type known as a Dobsonian mounting is the sturdiest and easiest that I’ve worked with. A Dobsonian mount makes it very easy to point the telescope to an object in the sky (especially if you spring for a simple laser-finder) and to keep the object in sight and steady once found. And if you’re observing with students or young kids, having a telescope that is on a steady and solid mounting is crucial.

Once you have your telescope picked out, the second step is to get a handful of eyepieces to use with it. Eyepieces magnify the image of the telescope, with the general rule that for a specific instrument smaller eyepiece focal length yields higher magnification. If you’re looking at large objects like the Moon or star clusters, you’ll want to use an eyepiece with a longer focal length (e.g., 25 mm). Then, when you want to zoom in on lunar features or try to split very tight double stars, you use an eyepiece with a shorter focal length to magnify the view. Most telescopes come with two or three eyepieces, and this is usually plenty for the beginner.

Finally, you need to know how to find the objects in the sky you want to view. I tend to eschew computerized mounts that point the telescope for you or tell you where to point it, because I think part of the fun is becoming familiar with the night sky yourself. But you’ll need some good resources to get you started. A quality star atlas is a must (I use the Cambridge Double Star Atlas), but it’s not much to go on if you’re just beginning. I’ve found James Mullaney’s Celestial Harvest to be an excellent guide to highlights in each constellation, and a tool like Guy Ottewell’s Astronomical Calendar (which unfortunately won’t be published after this year) lets you know what planets and constellations to spot when.

Then comes patience. Wait for clear nights and determine what constellations will be overhead. Do a bit of reading before you head out (or take a red flashlight with you to read at the telescope) and simply try to become familiar with the objects in one or two constellations at a time. Don’t feel like you need to learn the entire sky immediately. This month, for instance, Leo is a great place to start, from the lovely double star Algieba in the Sickle of Leo’s mane, to Jupiter and its moons just below the constellation (always a wonderful sight to start with), to the sweep of galaxies beyond Leo’s tail (though you’ll need to get away from the city lights to really appreciate these).

You’ll be amazed at what passes over your head each evening, generally unappreciated and unobserved, but within reach with a simple, good instrument.

This column first appeared in the Kankakee Daily Journal.

October Skywatch

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Sorry this is a bit late folks, but here’s my local astronomy column for this month:

This month, the skies favor the early riser. As Saturn slips toward the western horizon in our evening skies, Jupiter, Venus, and Mars take center stage throughout October in the skies before dawn. If you are someone who prefers to rise early, you are in luck. If you’re someone who tends to sleep in, set your alarm and treat yourself to a view of these bright objects at least a few times this month to see the steps in the eastern sky. I’ll give you a breakdown of the performance so you know what particular dates to watch for.

First though, a quick re-cap of the biggest celestial event of last month: the total lunar eclipse, which brought the current tetrad of total eclipses to a conclusion. Last year I had to bribe my astronomy students to rise before dawn to see the eclipse, but this time it was easily visible in the early evening sky. We shut off the lights on our side of campus, set up telescopes around the perimeter of the planetarium, and then waited for the sky—which had been cloudy all day—to clear. It did just in time, and we were able to view the duration of the eclipse in clear, dark skies from the heart of Bourbonnais. It was a sight, I trust, that few students will soon forget. (Several took pictures of the eclipse and have been posting them to social media under the hashtag #OlivetAstro.)

BloodmoonTimeLapse
Time-lapse of the lunar eclipse taken by ONU student Nick Rasmussen.

Now that the Moon is past full, it’s slipped from the evening skies and does not rise until after midnight. Its display isn’t over though, as it moves to the morning sky to join the planets before daybreak as a slender crescent. And that’s the first movement of this act you should catch these October mornings: set your alarm and rise before dawn on either Thursday, the 8th, or Friday, the 9th (or both). If the sky is clear, you’ll see three bright planets strung out in a line pointing down toward the eastern horizon.

The highest and brightest of these is Venus, which rises at about 3 AM and is high in the eastern sky before sunrise. Mars trails it to the east, and below them both is bright Jupiter. On the morning of the 8th, a thin crescent Moon rides just above Venus. By the next morning the Moon has dropped to join Mars and Jupiter as an even thinner crescent lower in the east. The slanted line of the three planets in the morning sky is a powerful illustration of the disk of our solar system, viewed from our tilted angle on the planet Earth.

Moving forward through the month, Venus falls eastward against the background stars each month, while Jupiter and Mars rise farther into the west. Jupiter passes by Mars on the morning of Saturday, the 17th, for the closest conjunction of this planetary arrangement. The bright giant planet passes within half a degree of the ruddy red planet. That’s about the diameter of a full Moon. At that distance, both planets could be visible in the same field of view through a telescope eyepiece.

It’s that ruddy red planet on which NASA scientists last month found the best evidence yet of running water on its surface. They studied the composition of dark tracts on Martian hillsides that change with the seasons and concluded these formed by briny water seeping out and staining the Martian surface.

Finally, as Venus continues its eastward motion against the background stars, it passes by Jupiter on the morning of Sunday, the 25th. Though the two planets are within a degree of each other (twice the diameter of a full Moon), this may be the most conspicuous conjunction of the month, as Jupiter and Venus are the two brightest planets in the sky. On the morning of the 25th and the following morning, they’ll form a brilliant pair with Mars trailing below them to the east.

Of course, their apparent closeness is only an illusion in our sky, the same way the light from a nearby lighthouse might appear close to a ship passing along the horizon. It’s only a matter of perspective. In reality, millions of miles of empty space separate those bright lights in the night.

This column first appeared in the Kankakee Daily Journal.

On blood moons and tetrads

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lunar eclipse
“Lunar eclipse April 15 2014 California Alfredo Garcia Jr1” by Tomruen – [1]. Licensed under CC BY-SA 3.0 via Commons – https://commons.wikimedia.org/wiki/File:Lunar_eclipse_April_15_2014_California_Alfredo_Garcia_Jr1.jpg#/media/File:Lunar_eclipse_April_15_2014_California_Alfredo_Garcia_Jr1.jpg

There is a lunar eclipse coming the end of this month, and depending on who you ask it is significant for different reasons. In fact, there has been a lot of hype about this particular eclipse (or rather, series of eclipses) in some Christian circles with the term “blood moon tetrad” often being used in conjunction with prophetic claims. I’m certainly not a specialist in Biblical prophecy, interpretation, or the history of Israel, but I can unpack some of the sensationalized terminology here and help sort out the science behind the hype.

Let’s start with the term “blood moon.” The popular press has recently started using this term to refer to a lunar eclipse. Lunar eclipses happen quite frequently, usually twice a year, when the full Moon passes into the Earth’s shadow. This causes the Moon to fade in brightness over the period of a couple hours and often take on a deep red hue due to the Earth’s atmosphere and the way it scatters light.

Consider how the sky looks during a sunset: even though the Sun is hidden beneath the horizon, the atmosphere bends the red portions of sunlight toward us. From the Moon, during a lunar eclipse, the Sun is hidden behind the Earth. The glow of a ring of sunsets casts that red light onto the Moon’s surface, making it appear duly reddish or “blood red.” This effect can be heightened if the Moon is near the horizon, depending on atmospheric conditions.

So what about “tetrad”? There are different types of lunar eclipses. If the Moon only moves partly into the Earth’s shadow, it’s called a partial lunar eclipse. The eclipse of this month is the last in a series of four total eclipses, in which the Moon passes through the darkest portion of the Earth’s shadow. A series of four total lunar eclipses without any partial eclipses between is known as a tetrad. This current tetrad includes the total lunar eclipse of last April as well as the eclipses of April and October of last year.

How rare are such series of eclipses? Glancing through my copy of NASA’s huge “Five Millennium Canon of Lunar Eclipses,” which included information on all lunar eclipses from 2000 BC to 3000 AD, I see that over the past thirty years there was a tetrad in 2003/2004 and 1985/1986 (as well as several lunar “triads”). According to the website EarthSky.org, there will be eight tetrads in the twenty-first century, while the years 1701 to 1899 had none at all. There were five in the twentieth century.

So what does this all have to do with Biblical prophecy? According to some sources, this particular tetrad is unique because it lines up with specific Jewish holidays. Last year, the first lunar eclipse of the series fell during Passover, as did the eclipse of April of this year. Last year the October lunar eclipse was during Sukkot, or the Feast of Tabernacles, which again corresponds with this month’s eclipse.

The important thing to remember though is that the Jewish calendar (unlike ours) is a lunar calendar; its months correspond with the actual phases of the Moon. Both Passover and Sukkot begin on the fifteenth day of the Jewish month, which usually corresponds with the full Moon. And because lunar eclipses only happen when the Moon is full, it’s not strange there would be occasional line-ups between these holidays and a series of lunar eclipses. How occasional? Again, according to EarthSky.org, this has happened eight times since the birth of Christ.

And here’s where the prophet interpreters come in, offering links between the years in which a tetrad of lunar eclipses corresponded with these holidays and important events in the history of Israel. But that’s the problem: history is a complex, messy business, and the human mind is hard-wired to find patterns everywhere, even where they don’t exist. Plus, these “significant events” are subjective: how widely do you want to interpret what events are actually important? The tetrad of 1493-1494 is linked to the expulsion of the Jews from Spain, for instance, but the order for the expulsion wasn’t signed in these years and the persecution lasted for decades. Making 1493-1494 especially significant is arbitrary. And other events that would seem to be significant are ignored: there was no lunar tetrad, for instance, during the Holocaust. Finally, I should add that this whole claim of prophetic significance is offered by individuals outside the Jewish community with little insight or regard into what that community would actually consider culturally or historically important in their own past.

In my mind, searching for codes in the night sky is much less useful than simply appreciating the grandeur of astronomy for what it is. And this month, regardless of prophetic forecasts, we have the chance to witness one of nature’s most impressive spectacles. The “blood moon tetrad” will conclude with the total lunar eclipse beginning the evening of Sunday, September 27th. (If you’re still looking for cosmic coincidents, here’s another one: my birthday is September 27th.)

The full moon rises in the east at sunset that evening. By 9:15 the Moon has begun to enter the darkest portion of the Moon’s shadow, marking the most vivid phase of the eclipse. It will be at its darkest at about 9:45, and the moon will begin to emerge from deep shadow at about 10:20. The Moon will not be completely out of the Earth’s shadow, however, until after midnight. As far as visibility, this will be an easy lunar eclipse to observe—taking place when the Moon is high in the early part of the evening. (Last year I had to make students get up before dawn to spot the eclipse.) So definitely take the opportunity to wonder and ogle, but try not to prognosticate.

This column first appeared in the Kankakee Daily Journal, August 28th, 2015.

August offers a look at Lyra

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When I talk to people about observing here in town, they often bemoan the fact that light pollution makes stargazing all but impossible from within the city limits.

Though it is true that observing from an urban setting doesn’t compare to an experience under truly dark skies, it’s certainly not the case that there’s nothing to see from one’s own backyard or even sidewalk.This month I’ll consider some of the sights in the constellation Lyra, which is almost directly overhead throughout August in early evening.

Lyra is a tiny constellation, but it holds a wealth of lovely double stars that are bright enough to be seen without a pilgrimage to the deep, dark countryside.

The constellation Lyra is easy to find on clear nights. Vega, its brightest star and the brightest star of summer, is nearly overhead at sunset. Vega marks one apex of the famous Summer Triangle, an asterism of three bright stars high in the summer skies. Lyra itself though is small formed of a triangle of stars attached to a larger parallelogram. Classically, the constellation was seen as a harp or lyre.

Lyra

My observations are made with a six-inch reflecting telescope from my own yard in Kankakee, but a smaller telescope will reveal these sights as well. You’ll want to use eyepieces that give a relatively low magnification. (I used about 40x. Calculate the magnification of your eyepiece by dividing your telescope’s focal length by the focal length of your eyepiece. A shorter eyepiece focal length gives greater magnification.)

Sometimes you want higher magnification, as when you’re viewing the planets or the Moon and want to see details, but for the following views a lower magnification is better.

Start your tour with Vega, especially if you’re new to stargazing. A single star doesn’t look much different through a telescope, but this will give you a chance to align your finding scope (if your telescope has one) and test your instrument’s focus. It will also give you an idea of the seeing conditions for the night. If you can focus Vega down to a brilliant, sharp point, and if you can see one or two of its dimmer companions in your telescope’s field of view, you should be able to spot the rest of the objects in this list.

Hop down from Vega to Zeta Lyrae, the dim star where the triangle meets the parallelogram. This is one of the many double stars in Lyra. Double stars are great targets for light polluted skies. Unlike nebulae or galaxies, they are fairly bright and thus easy to enjoy even from one’s own backyard. Through even a small telescope, Zeta Lyrae is revealed to be a wide, uneven double, and many observers report seeing a beautiful color contrast between the component stars.

Moving up to the third star of the tiny triangle that makes up the top portion of Lyra, we find Epsilon Lyrae, one of the most popular double star systems in the sky and an example of why some observers (like me) get so excited about double stars. At 40x you may simply see what looks like a wide pair of white stars. But if you increase your magnification (I used 130x), you’ll see that each of these stars is actually itself a pair of stars. The entire system is known as the “Double-Double.” You’ll need a steady eye and good seeing to split them, but you’ll know if you’ve succeeded by noticing the orientation of each tight pair: they’re inclined at ninety-degrees to each other.

Moving back to a lower magnification, each of the stars at the apexes of Lyra’s parallelogram is a treat.

Delta Lyrae is a wide double star in a diffuse cluster of stars. One of the components is a lovely orange in contrast to the surrounding blue stars.

Beta Lyrae also is a group of colorful stars. (The Ring Nebula is nearby, halfway between Beta and Gamma Lyrae. From my front yard, the Ring Nebula at 70x looked like a faint smoke ring, barely visible.)

But my favorite sight of all in Lyra is a bit off the beaten path and not terribly well known. It’s sometimes called the “Double-Double’s double,” but I think it’s actually nicer than the more famous Double-Double. It’s a pair of double stars, like the Double-Double, known as Struve 2470 and 2474. They’re dimmer than the pair that make up Epsilon Lyrae, but because the components are farther apart they’re easier to split. They also have more marked colors, the brighter components appearing yellow in contrast to the dimmer bluish companions. Moreover, by some cosmic coincident the pairs are orientated in the same direction so they indeed look like almost perfect twin double stars in a single telescope eyepiece. This view alone would be proof enough for anyone who says the city skies are too bright to hold telescopic wonders.

doubles
Struve 2470 and 2474, the “Double-Double’s Double,” image from bestdoubles.wordpress.com.

This column first appeared in the Kankakee Daily Journal.