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    My Journey through the Astronomical Year

    Think of this as a "companion text" to this, the main web site. Not required reading, butI hope you'll find it interesting and helpful.

Sky, Eye, and Camera: Special Viewing/Photo Ops for September 2014

Note: This is my first installment of a new feature. It’s a modification of the old “events” post and still is a guide to special events for the month – things happening in the sky that do not repeat from month to month but are special to a particular date. To this I have added – and put emphasis on – information about events that are particularly suitable for capture as photographs – especially photographs that convey a sense of being there and are taken with ordinary cameras.  This is in contrast to the traditional astronomy images that use special cameras to show us things we cannot see with the naked eye by taking long exposures and gathering much more light, usually using a telescope as the lens. Greg Stone

 

September 2014 gives us several special opportunities for nice, naked-eye views of stars and planets that also provide excellent photo opportunities, especially if you have a DSLR camera – or something similar where you can adjust the exposure.

August 2014 "super" Moon. (Photo by Greg Stone)

August 2014 “Super” Moon. (Photo by Greg Stone) Click image for larger version.

September 8, 2014 – “Super” Moon rising in the Earth’s Shadow/ Belt of Venus

I can’t get real excited about the “Super” Moon idea – we’ve had two this year already, and they’re really not all that unusual, or for that matter not quite as “super” as the word makes them sound.

But the full Moon rising is always a pretty sight and a very easy subject for photographers. One alert, though. The Moon is really quite small – half a degree – and so your picture may show a Moon much smaller than you remember seeing with the naked eye. This is because the full Moon  ALWAYS appears to be much larger to us when it’s near the horizon, whether “super” or not. A friend asked me recently why my picture of the Moon conveyed this sense of what he saw, while others didn’t.

The answer is simple. I used a small telephoto lens. Technically it was an 80mm, but because of the sensor on my camera, you have to add a factor of 1.6 to that to get the 35mm – or “full frame” equivalent. So in this case it was like using a 128mm telephoto on a 35mm camera.  Lots of simple cameras come with zooms that provide at least that much magnification. Use more magnification and you may end up with a real nice picture – but it may make the Moon look a lot bigger than what people saw with their naked eye.

That brings me to another major point. My whole approach to night sky photography is to try to convey a sense of being there. For that reason I don’t overdo the sensitivity of the CCD – that is, I don’t set the ISO real high – and I do keep the exposures relatively short. With the full Moon in August, I had the ISO set at  1600 – which meant I had a little noise to clean up with the editing software – and I could take the-picture at 1/160th of a second – that’s fast enough to hand hold even with the 128mm telephoto – and the the F-stop was 7.1, small enough to provide some reasonable depth of field.

That last is critical. The Moon is at infinity, but you want to also include some foreground subjects at close and mid-range to give a sense of proportion to the objects in the sky.

Moon rise time varies by your location. Where I am on the eastern seaboard of the US, the Moon will be rising roughly 20 minutes before the Sun sets on September 8th. This is going to provide an interesting  opportunity, I think, to catch the Moon in the shadow of the Earth and/or the Belt of Venus. These appear in the east shortly after sunset and after about 15 minutes start melding into the night. The shadow will be a darker blue than the sky above it and extend perhaps a fist above the horizon.  The “Belt of Venus” will be a rosy band above the shadow. Bottom line: I think the most interesting shots will be taken about 10-15 minutes after sunset.

Of course, much depends on local weather conditions. For me the trick is to know where the Moon will be rising – just a tad south of east in September 2014 – and find a spot that not only gives me a clear horizon in that direction, but also provides some interesting foreground objects to go along with the Moon.

September 20, 2014 – Algol at minimum brightness

This event – an eclipse of Algol – will be centered on 10:55 pm EDT; on the 17th a similar event will center on 11:06pm PDT. I’m not going to go into  detail about the “demon star” here. If you don’t know about it, you can read more in this earlier post.

What I do want to point out is it’s fun to see this star dim, then brighten over the course of a few hours, and if you like taking constellation pictures, it would be neat to get one of Perseus with Algol at full strength and one with Algol at full eclipse.

While these eclipses happen every few days, you’re lucky if you find one or two a month that come at a time convenient for you to watch – and then, of course, the weather has to cooperate.

September 22, 2014 – the  Fall Equinox

This is a fun time to get a picture of either sunrise or sunset. You don’t need to be right on this date -a day or two before or after will do fine. The basic idea is to show the Sun in relation to local landmarks and thus identify for yourself the general heading for east or west from any given spot.  Actually, a real nice project is to pick a scenic spot, take a picture of a sunrise or sunset as close to the Equinox as you can get, then do the same thing again from the same spot showing the Sun at the Winter and Summer Solstices and at the Spring Equinox. The four will then show the movement of the Sun along the local horizon in the course of a year.

September 24-30 – Mars and its Rival, Plus Saturn

Click for larger version - prepared from Starry Nights Pro screenshot.

Click for larger version – prepared from Starry Nights Pro screenshot.

I suggest you go out an hour after sunset and look southwest for three bright “stars” near the horizon. Two should have a reddish hue, one a yellowish hue – though honestly, with them all this close to the horizon the atmosphere may cause them to twinkle and change color.

Still, this is worth seeing and should provide an interesting photographic challenge. However, if you have been taking pictures of constellations, similar settings should work here. (I like to set the ISO at 6400 and expose for four seconds at F7.1 with the camera on a tripod, of course, and using a cable release. This, for me, gives a typical naked eye view – but you need to experiment. I also clean up the background noise in such photographs using Lightroom.)

The main attraction here is that Mars – the red planet – is near Antares, a red star. In fact, the name “Antares” means “rival of Mars” because its color rivals the obviously ruddy planet.  Saturn is farther away but has a distinctly yellowish hue. In the course of these six evenings, Mars will first draw a bit closer to Antares, then get farther away. Saturn will also get lower each night, though Mars is moving in a counter direction right now and will appear to hold its altitude – that is, be at the same height at the same time. Of course, all of these will get too close to the horizon and eventually set, so timing is important. I plan to start an hour after sunset, then see what works best over the next half hour or so as the sky gets darker, but Antares, Mars, and Saturn also get lower.

Again, the challenge for me is to include foreground objects and show the night sky as we really experience it.  Here’s a shot, for example, that I took last winter of Orion – with a quite bright Moon out of the picture to the left.

Orion as seen from the Town Farm in Westport, MA in the winter of 2014. (Photo by Greg Stone)

Orion as seen from the Town Farm in Westport, MA in the winter of 2014. (Photo by Greg Stone)

Crescent Moon and Planets  in September 2014

I see two photo opportunities to capture a crescent Moon near major planets. On September 20, 2o14, the Moon should be within about 6 degrees of Jupiter, both about one-third the way up the eastern sky an hour before dawn. As Jupiter fades, Venus may put in an appearance near the horizon, though it’s getting quite close to the Sun.

On September 27, 2014, Saturn will have an even closer encounter with the Moon in the southwestern sky at dusk. Yep – this is in the middle of the period suggested to capture Antares, Mars, and Saturn – so if the weather gives you a break you might get a crescent Moon as a bonus.

 

February 2014 Events: Obvious Jupiter, Morning Venus, Subtle Zodiacal and a timely wink from the Demon

Yep, you can’t miss Jupiter this month.  It’s well up in the eastern sky as it gets dark and brighter, by far, than even Sirius, the brightest star we folks in the north see.

What other special events are on parade this month? Well, the Moon provides a wonderful viewing – or photo op -with Venus in the predawn sky late in the month; the last two weeks of February will be a good time to look for that elusive Zodiacal Light about 80 minutes after Sunset, and if the weather on February 17 cooperates, we have a perfectly timed eclipse of Algol, the Demon Star, for folks in the Eastern Half of the US. ( There are other dates with the Demon available too for other parts of the world.)

So let’s start with Jupiter. You really can’t miss it even if you’re a beginner. In fact, if you’re a beginner this is a good time to let Jupiter be your guide to the Winter Hexagon. As mentioned in our “look east” post, you’ll find it in Gemini. Look to the southeast a couple of hours after sunset and here’s what you should see.

Click image for much larger version. To get the full beauty of this section of sky find an area with a clear horizon to the southeast and go out on a February evening a couple of hours after sunset. The chart shows what you'll see. The link below provides a small black-on-white version you can print and take into the field. (Prepared from a Stellarium screen shot.)

Click image for much larger version. To get the full beauty of this section of sky find an area with a clear horizon to the southeast and go out on a February evening a couple of hours after sunset. The chart shows what you’ll see. The link below provides a small black-on-white version you can print and take into the field. (Prepared from a Stellarium screen shot.)

Click here for a printable map of the above chart.

Jupiter reaches its highest point as it crosses to the south about 5 hours after sunset near the start of the month and closer to three hours after sunset at the end of the month. As the chart shows, Sirius will be lower and more to the south.

Moon and Venus team up for a Picture Perfect  Pre-dawn Sight

Venus is a morning star and really stays pretty close to the Sun this month, but as Sky and Telescope points out, there’s a great meeting of Venus and a thin crescent Moon on the morning of February 26. Here’s what to look for then.

Click picture for larger version.

Circle shows the typical view through ordinary binoculars – you may just be able to fit them both in the same field of view. Click picture for larger version.

Soft, elusive, and fascinating – Zodiacal Light

Mornings not your thing? Well from February 16 to March 2 the Moon will stay out of your way if you go out about 80 minutes after sunset and look for the elusive, zodiacal light. This is faint – sort of like the Milky Way – but its a pyramid of light rising up from where the Sun sets and going roughly halfway up the sky and leaning to the south.  To see it you must have dark skies pretty much free of light pollution. (A city to your west, for example, would likely ruin it.) And, of course, your eyes must be dark adapted.

Still, it’s a fascinating cloud of fine dust. Here’s what I said about it a couple of years ago – and it still applies:

You don’t need a totally clear horizon to see the zodiacal light, or binoculars, but you do need total darkness and that means little-to-no light pollution and no Moon. So you want to wait until a few days after full Moon to begin this quest. I feel I have a good shot at it from my favorite ocean-front observing point where I have a clear horizon to the west with no cities to create light domes there. Evenings in February and March – and mornings in September and October – are the best time for folks at mid-northern latitudes to look for this.

The zodiacal light is roughly the same intensity as the Milky Way, so if you can see the Milky Way from your chosen location, then you should be able to pick up this faint glow. Like the Milky Way, it stretches over a good deal of sky. It is widest near the horizon and gets narrower as it rises towards the zenith. You want to look for this starting  roughly 80 minutes after sunset. You can check for an exact time for your location by getting information from here on when astronomical twilight ends. (The drop-down menu on that page specifies the times for astronomical twilight.) As astronomical twilight ends you want to start looking. As with any faint object, your eyes need to be dark adapted, so I am assuming you have been out for at least 15 minutes with no white light to dazzle you. If you try to look for this earlier, you may confuse it with twilight. Much later and it is not as bright, for what we are seeing is sunlight reflecting off interplanetary dust particles – dust particles that orbit in the same plane as the planets – the area we call the zodiac – and thus the name for this phenomena, zodiacal light.

If you see it, reflect on this explanation from Wikipedia:

The material producing the zodiacal light is located in a lens-shaped volume of space centered on the Sun and extending well out beyond the orbit of Earth. This material is known as the interplanetary dust cloud. Since most of the material is located near the plane of the Solar System, the zodiacal light is seen along the ecliptic. The amount of material needed to produce the observed zodiacal light is amazingly small. If it were in the form of 1 mm particles, each with the same albedo (reflecting power) as Earth’s Moon, each particle would be 8 km from its neighbors.

For the metrically challenged (that includes me), that means one dust particle every five miles! And that causes all that light?! Awesome!

Now, about that Demon!

I wrote about Algol the “Demon Star” in this  posting for October, but it’ s still well placed for viewing in February, and if you look at the right time, you’ll catch it in mid-eclipse, which is cool. For those on the East Coast, the most convenient time will be roughly 7:45 pm. Technically, the eclipse goes on for about two hours with the lowest point – the star at its dimmest – at 8:44 pm EST.  But to appreciate this you should check it an hour before to see the normal brightness, then look again at 8:44 pm. Of course, you could start at 8:44 pm and note how it brightens during the next hours. Either way, it will convey why ancient star gazers considered this the “Demon Star.” These events happen often enough for them to notice it dimming every once in a while – sort of winking at them – and no other bright star does that, so it’s easy to imagine the stories that would be told.

Every 2.3 days Algol dims like clockwork, but it is only at its dimmest for about two hours, so to see it in this condition you really need to be watching at the right two hours. Fortunately, there are several places that will give you a list of times when this occurs – but many of these times will be while normal people are sleeping – and many more will be during daylight hours. However, each month there should be one or two dates when it is really a good time for you to catch Algol doing its thing.

Most of the listings I know of for Algol “minima” give date and time in Universal Time. What I like about the one at Sky and Telescope magazine, is it will calculate a list of coming Algol minima for you – and give you the Universal Time, plus your local time. So it’s easy to glance over it and see when it will be most convenient – weather permitting – for you to take a look. In my case, February 2014 gives me a couple of opportunities worth noting:

  • 02/14/2014 @ 11:55 pm
  • 02/17/2014 @ 08:44 pm

With winter weather it’s easy to get clouded out, so the more opportunities the better your chance of seeing something. I find these eclipses amazingly elusive and rarely see one, maybe because I think there’s always going to be another opportunity – and there will, but . . .

Look north in September 2013 – the king’s on the rise!

Yes, that’s Cepheus, the King – remember that Cassiopeia (the “W” ) is the Queen. Though Cepheus makes a familiar “home plate” asterism, it’s not nearly so memorable as the “W” of Cassiopeia, primarily because its stars are dimmer than those of the “W.” In fact, you might have difficulty picking it out at first, but here’s a tip: Follow the familiar “Pointers” of the Big Dipper to the North Star – then keep going. The first bright star you meet will mark the tip of the Cepheus home plate. (It’s about one fist away from Polaris – the Pointer stars are nearly three times that far in the other direction.)

Also coming up below the “W” is the “Bow” asterism that marks Perseus, who is carrying the head of Medusa, which contains the “Demon Star,” Algol. We’ll take that up next month when they’re higher in the sky and easier for all to see. Here’s a chart.

Click image for a larger version. (Developed from Starry Nights Pro screenshot.)

For a printer-friendly version of this chart, download this.

To review the connecting mythology, which helps me remember the related constellations, here’s the story in brief.

Cepheus and Cassiopeia have a daughter Andromeda whose beauty makes the sea nymphs jealous. They enlist Poseidon to send a sea monster to ravage the coastline of Ethiopia, the kingdom of Cepheus and Cassiopeia. To appease the monster, the good king and queen chain Andromeda to a rock along the coast, but Perseus rescues her and together they escape on Pegasus, his flying horse.

You meet Andromeda and Pegasus – the flying horse is much easier to identify as the “Great Square” – in the “look east” post this month. Also in the “Look East”  post we detail the “Three Guides,” three stars that mark the zero hour in the equatorial coordinate system used to give a permanent address to all stars. The first of those Three Guides is Beta Cassiopeia, visible in our northeastern sky, and so on the chart with this post.

Moving from mythology to science, Cepheus is probably best known today for a special type of star called a Cepheid variable. This is a star that changes in brightness according to a very precise time table. What’s more, it was discovered that the length of a Cepheid’s cycle – that is the amount of time it takes to grow dim and then brighten again – is directly related to its absolute magnitude. The absolute magnitude of a star is a measure of how bright it really is as opposed to how bright it appears to us. (How bright it appears is, of course, related to how far away it is.) That makes Cepheid variables a sort of Rosetta Stone of the skies.

It is relatively easy to time the cycle of a variable, even if the star is quite faint from our viewpoint. These cycles usually cover a few days. If you can identify the length of this cycle, you then can know the absolute magnitude of a star. And if you know its absolute magnitude, it’s a simple matter to compare that to how bright it appears to us and thus determine its approximate distance from us.

This is a huge breakthrough. Without Cepheid variables astronomers were at a loss for determining the distance of anything that was more than a few hundred light years away. The distance to such “close” stars could be determined using a very common method known as parallax – that is, determining how the star appeared to change position slightly from opposite sides of the Earth’s orbit. But that change in position is extremely tiny and difficult to measure even with very close stars. With the Hipparcos satellite and computer analysis, it has been possible to use this parallax system for stars as far as 3,000 light years. But that still is close by astronomy standards. (Keep in mind our galaxy is about 100,000 light years across.) But Cepheid variables can even be found in other galaxies. In fact, they played a huge role in proving that “spiral nebulae” were really other “island universes” – that is, other galaxies. The Hubble Space Telescope has found Cepheids out to a distance of about 100 million light years – a huge leap from the 3,000 light years we can reach with the parallax method.

There are other ways of making an educated guess at an object’s distance, and they frequently are quite complex and indirect. But the Cepheid variable has been one of the most important tools in the astronomer’s tool kit for the past century. It was in 1908 that Henrietta Swan Leavitt, a $10.50 a week “calculator” at Harvard Observatory noticed a pattern while doing tedious work cataloging stars and saw it’s importance. Though she published a paper about it, she never really received the credit she deserved during her lifetime for this breakthrough discovery.

So when you look at this “home plate” in the sky, see if you can find the fourth magnitude star, Delta Cephei – it’s not hard to spot under good conditions. (See the chart above.) When you find it, pay homage to it for the key role it has played in unlocking the secrets of the universe – for once astronomers know the distance of an object they can make all sorts of deductions about its composition, mass, and movement.

Events February 2011: A great “Luna-See” month, plus goodby Jupiter, hello Saturn and basking in the Zodiacal Light?

The apparent wobbling of the Moon shown here causes "librations" which result in our being able to see about 59% of the Moon, even though it always keeps the same face towards us. (This work has been released into the public domain by its author, Tomruen.)

 

 

February 2011: A Great “Luna-See” Month

What makes February 2011 a great “Luna-See” month? Well, the cycle of the Moon is pretty close to being in step with the calendar we all use this month. But the truth is, the Moon is special and always worthy of our attention if for no other reason than it is constantly changing, while most everything else in the sky stays the same – or takes more than a human lifetime to change noticeably.

What’s more, people just take the Moon for granted, and I find that even many experienced sky watchers either haven’t noticed – or can’t explain – some of the major motions of the Moon and why it is where it is at any given moment. So let’s engage in a little “Luna-See” this month and see if we can untangle in simple fashion the motions of the Moon and how these motions gives us a constantly changing show night-by-night and moonth-by-moonth!

No – that’s not a typo. A “moonth” is simply my term for the lunar cycle. Our months vary in length. But the lunar cycle – the time it takes to go from one New Moon to the next – is a constant 29.5 days. The Moon actually goes around our planet in 27.3 days – but by the time it completes one orbit our planet has moved along in its path around the Sun and the Moon has to play catch-up. To get to the position we call “New Moon” – the position where it is directly between us and the Sun – takes 29.5 days, or one “moonth!” ( OK, there’s a correct term for this – it’s called the “synodic month” or a “lunation.” It’s just that “moonth” makes more sense to me – maybe i should contact Mr. Webster 😉

Since 29.5 days is not the same length as our calendar month, the “lunations” get, well, out of sync with the calendar. But in February 2011 the New Moon occurs pretty close to the start of the month – February 3 – so that’s where we’ll start this little adventure in “luna-see.”

Ideally, this should be a three-pronged discovery adventure – first, attack the problem with your mind by reading this. But for me abstract descriptions don’t hold much water, so when you’re through reading what follows, I urge you to move on to:

The real fun, though, is to go out, look up at the Moon, and in your mind be able to picture the entire Earth/Moon/Sun tableau – to see those things that are out of sight and understand how they contribute to what is in sight – or more simply, to know why the Moon appears the way it does, in the place in our sky that it occupies at any particular moment. So let’s get started.

 

February 3, 2011, 2:31 UT – New Moon – Everyone Wants to See the New Baby!

Notice the precise time? That’s important for new Moon junkies who like to see what is the youngest Moon they can see. I’ve never been addicted to this game, but I’m a casual player. It’s fun and a challenge open to anyone. And a crescent Moon can be simply beautiful, especially if paired with some nearby bright planets. What you need is an unobstructed western horizon and very clear skies because when you’re looking for something near the horizon, you’re looking through a lot of air and even small clouds that build up over the course of distance to form a haze near the horizon.

The new Moon occurs when the Moon is between the Earth and the Sun. For February 2011 that is at 2:32 UT. (To convert Universal Time – UT – to your local time, go here, find your time zone, then use the chart on the bottom right of that page to see how many hours you should add or subtract for your time zone.) At new Moon we can’t see the Moon because the side facing us is unlit, and even if it were a tiny bit lit, it would be overwhelmed by the glare of the Sun. But because new Moon occurs so early in the Universal Time day, there’s a slim possibility some of us in North America and points west may see it on February 3 – it just depends on where we are – and, of course, the weather.

A young Moon with Jupiter about 30 degrees above it, as seen from 42°N 71°W about 45 minutes after sunset on February 4, 2011. Click image for a larger version. (Stellarium screen shot.)

People have reported seeing Moons as “young” as about 12 hours. A more realistic goal is a 20-hour Moon. Exactly how old the Moon is after sunset on February 3 or 4 – depends on your exact location. I’m roughly at 42°N, 71° W, and on February 3 right after local sunset the Moon will be about 18 hours old. If I’m real lucky I may see that – and if I do, it will be the youngest Moon I have seen. A much more realistic task is for me to look for it the next night, February 4. At sunset on February 4 at my location the Moon will be close to 40 hours old.

This looking for the first slither of Moon is a little game that’s fun to play. The sky is usually too bright for you to see it right after sunset. You have to wait a while – but the problem is, the longer you wait, the lower the Moon gets in the sky. So on the one hand, the sky is getting darker making it easier to see the Moon – but the Moon is getting lower making it harder to see! Binoculars help – but use caution. Wait until you are sure the Sun has set. You will be looking in the same section of sky for the Moon as the Sun just occupied, and you don’t want to accidentally view the Sun and burn your eyes!

In my case on February 4, 2011, the Moon sets almost two hours after the Sun. This means that about 45 minutes after Sunset – when the sky is getting pretty dark – the Moon will still be about 10 degrees above the western horizon and just a tad north (3 degrees) of where the Sun set – which, if I’m lucky and have really clear skies to the west – will be easy to see. On February 3 it’s a much different story. Even at sunset the Moon is only eight degrees directly above where the Sun set. (Remember, your fist held at arm’s length covers about 10 degrees.) But the Moon sets in just 45 minutes, so if I catch it at all, it will be while looking through a lot of air and against a bright background, and it will be a very dim sliver. My strategy will be to wait until about 10 minutes after sunset, then start scanning with binoculars.

 

February 11, 2011, 7:18 UT – First Quarter and a Close Encounter of the Pleiades Kind

This is the view on February 11, 2011, about 45 minutes after sunset for my location - 42° N, 71° W. The Moon passes about one degree beneath the Pleaides star cluster and you should be able to see both in the same binocular field of view, but the Pleiades will be washed out and dim because of the brilliant Moon light. Exactly how close the Moon is to the Pleiades depends on your location. Remember, it is constantly moving eastward - while at the same time, it, and all other objects in the sky, appear to be moving westward because of the rotation of the Earth. (Prepared from Starry Nights Pro screen shot.)

Now seeing the Moon is no challenge if your skies are clear. Each day at sunset it has moved about 12 degrees farther east as it circles the Earth. This means it’s climbing up our sky – on a slant, since it follows an arc across the sky, not a straight line – but higher each night. Tonight it will be about 70 degrees high about 45 minutes after sunset. And, of course, more and more of it is lit each night. Now we see about half of the Moon – that is half of what we will ever see, but really just one quarter of it. Nearly half of the Moon remains hidden to us all the time. This is because the Moon keeps the same face towards us. That is, it takes it just as long to spin once on its axis as it does for it to revolve once around the Earth. If the Earth did that as it journeyed around the Sun, half the Earth would be in constant sunlight, the other half in constant darkness! The other half of the Moon isn’t constantly dark, however. It does get sunlight on it, just as the half that faces us does – it’s just that the other half never faces us. Well, not quite – for various reasons we get little peeks at part of it, and when you add all these up we actually see about 59% of the Moon’s surface.

But as you look at the first quarter Moon in our sky, think about where it is at that moment – and more importantly, think about where the Sun is at that moment. The Sun moves about 15 degrees each hour. So if you are seeing the first quarter Moon about an hour after sunset, then the Sun is already about 15 degrees below your horizon. Can you picture it in your mind? Sort of like a huge flashlight, shining on and lighting half of it? Of course, you see only half of the lit portion, which is why this is called “First Quarter.”

For me, in the Eastern Time Zone of the US, first quarter Moon actually occurred at 3:18 am! So when I see it on the night of February 11 it’s about 15 hours later and the Moon is well on its way to being eight days old – it is past first quarter and a little more of it is lit. As I say, it is constantly changing – something you can see for yourself as you follow the “terminator,” the line between sunshine and darkness. Do this with binoculars a or telescope over the course of a few hours, and if you are a careful observer, you will see a difference.

The Moon is also about as far north as it will get this month – and thus almost as high in our sky as it’s going to get in February. Actually, for me it reaches its highest point a couple of hours after sunset on February 12 when it is 72 degrees high. Why? Because at that point in its travels around the Earth, it’s on the side where the Earth is leaning towards it – at least for us Northern Hemisphere observers. This is explained in detail in the projects:


 

February 18, 2011, 8:36 UT – Full Moon – Great for Lovers but Not Always Loved

Now here we are at full Moon - as illustrated by the "Luna-See" model.

Ah – the moment we’ve been waiting for – when we see the full face of the Moon – well, the full face that faces us is lit because the Moon is opposite the Sun in our sky. Focus on that word “opposite.” It’s very important for understanding the north-south motions of the Moon, and here’s a good thing to remember: The full Moon always rises directly opposite the setting Sun. This is most dramatic in June and December. Again, sticking to my own Northern Hemisphere as an example, the December Sun sets in the southwest – so the Full Moon in December rises in the northeast – directly opposite the setting Sun – not just on the other side of the sky, but in the other quadrant. And in June the Sun sets in the northwest, so the full Moon rises in the southeast. That summer full Moon mimics the path of the winter Sun – that is, it crosses our sky in a low arc to the south. And the winter full Moon? It mimics the path of the summer Sun and crosses our sky in an arc, high above us.

The abbreviated explanation for this is that the Moon goes through the same north/south motions in our sky every month – well, every “moonth” or lunation – that the Sun goes through every year. Why? It’s all because the Earth is tilted on its axis. The Sun is high in our sky when that tilt has us leaning towards it. It’s low when we’re leaning away from it. But we don’t change the way we lean – what changes is that we go around the Sun and so sometimes we’re leaning towards it, sometimes away from it. And the Moon? It goes around us each month. So sometimes it is on the side of us that leans towards the Moon, and thus it’s high in our sky, and sometimes it’s on the side that leans away from it.

Again – this explanation may be sufficient for you, but if not, I urge you to build the simple models and explore these motions on your own. You should find it much easier to get the geometry clear in your mind if you do the projects.

The full Moon is, of course, a beautiful sight – but amateur astronomers won’t always agree. For them – especially if they use telescopes – the full Moon is a bother. If you look at the Moon with your telescope, it is rather uninteresting because the sunlight is shining straight down on it and so there are no shadows to indicate how high a lunar mountain is or how deep a lunar crater. Worse yet, the Moon is so bright, its light is washing out many of the other fine telescopic sights that the night sky holds.

However, sky watchers just learning the bright stars may welcome a full Moon because the sky is less confusing. Instead of seeing a couple of thousand stars – which can be very confusing – they see only the brightest stars, and these are easier to get straight.

During the first half of the lunation – the “moonth” – the Moon is in the sky right after sunset. As it went from new Moon to full, it got higher in the sky each night and it stayed with us longer, setting roughly about 50 minutes later each night. By the time it was full, the Moon rose as the Sun set, then set in the early morning, just before the Sun rose.

 

February 24, 2011, 23:26 UT – Last Quarter Fun for Insomniacs and Early Risers

Last quarter Moon rises in the southeast near the bright star, Anatares, in the early morning of February 26. Here's how it would appear at about 2:30 am EST from 42°N 71°W. Click image for much larger version. (A Stellarium screen shot.)

OK, last quarter is not the same as first quarter. I say that with emphasis because I see too many books that treat the Moon in detail from new Moon to full Moon – then dismiss the second half of the cycle as if it were just a repeat of the first half. Anyone who believes that’s the case is guilty of what Holmes accused Dr. Watson of when he said: “Quite so . . . you see, but you do not observe.”

Top image shows how the waxing Moon reveals the Sea of Crisis on its eastern limb as sunrise moves from east to west across the Moon. In the second half we see the Moon a few days after full when it has started to wane. Notice that it shuts down the eastern side first - the Sea of Crisis was the first major sea revealed and it is the first major sea to return to darkness as the sunset line moves from east to west across the Moon.

On a broad scale, to the naked eye, things are happening in reverse during the second half of the”moonth.” The first crescent Moon we see a few days after new Moon reveals a beautiful, round sea – Mare Crisium (Sea of Crisis) – near the Moon’s eastern limb. After full Moon, this will be the first area to go dark.

Yes, at last quarter we are seeing just half of the face of the Moon again, but this time the Sun is coming from the other direction. From new Moon to full Moon the Sun is rising. The terminator – the line between darkness and light – marks the sunrise point on the Moon. This change becomes most obvious when viewing with binoculars and small telescopes, for it means that when a crater is highlighted it is the inside, western wall of the crater that is lit and the outside eastern wall of the same crater. From full Moon to new moon, that sequence is reversed. Now the same crater will have the inside of its eastern wall lit and the outside of its western wall. So what? So things have a different feel. Seeing is our most powerful sense – but we also tend to take things for granted – take a “been there, seen that” attitude, and the result is that in the fine words of Holmes, we see, but we do not observe.

When you observe the Moon carefully, you will notice that many familiar features look quite different during the second half of the lunar month. In fact, I frequently find myself disoriented when I look at the Moon in its waning phases. I have to go to my charts to be sure I know what I am looking at because sometimes very familiar craters and mountain ranges look quite different under the different lighting.

All of this should be clear if you simply stop and think for a moment about where the major players are – where the Moon is at the moment and where the Sun is at the moment. When we did this with the waxing crescent Moon we knew the Sun was below the western horizon. With the waning crescent Moon the Sun is below the eastern horizon, throwing its light from the west side of the Moon towards the east. That’s the opposite of what it was doing with the waxing crescent Moon.

Since the Moon comes up about 50 minutes later each night, it is not long after the full stage that the Moon isn’t visible in the night sky until several hours after sunset. By the last quarter it’s generally not visible until after midnight. And the waning crescent Moon rises just a few hours ahead of the Sun.

This, of course, means that if you want to observe the Moon during these later phases you need to either get up early – or not go to bed. That works for insomniacs, but is difficult for the schedule of most people.

 

The Moon in Daylight

From time to time someone comes to me quite surprised that s/he saw the Moon in daylight. Yes, you can see it in daylight. It is visible most days. It is just not obvious. And some days are better than others if you want to look for the Moon in daylight. At new Moon and full Moon the Moon is not likely to be visible in daylight. The rest of the time it is – you just have to know where to look and have, of course, clear skies. And you have to be prepared to see a pale shadow of what you see at night – although I must say it can be quite bright and impressive when near the first quarter or last quarter stages and when seen within a few hours of sunset or sunrise when the section of the sky the Moon occupies is still comparatively dark.

So here are a few good times to see the Moon during the day in February 2011.

February 11-15, 2011 – This is when the Moon is waxing between first quarter and full. Two hours before sunset – until sunset – look for the Moon high in the east. On each successive day it will be lower in the eastern sky at that time, but more of it will be lit. By full Moon it is below the eastern horizon until near the time of sunset.

February 20-24, 2011 – This is when the Moon is waning between full and last quarter. Look for it high in the western sky from sunrise until a couple of hours after sunrise. With each successive day the Moon will get smaller, but higher in the western sky.

At either end of the “moonth” the Moon is in a crescent phase and near the Sun. While it is in the daytime sky much of the day, it is very difficult to see and looking for it with binoculars or a telescope at such a time would be dangerous since you could accidentally look at the Sun instead and damage your eyes. That’s why we look for the crescent Moon in the hour or so after sunset, or the hour or so before sunrise.

 

Goodby Jupiter, Hello Saturn!

Not quite. Saturn has been with us for months, but only in the morning sky. And Jupiter will still be with us in March, but it will be getting too low in the west to observe it easily. So in practical terms, this will be the last month to get a real good look at Jupiter and its dancing Moons with binoculars or a small telescope. And it will be the first month that Saturn will get high enough in the sky before midnight to get a good look at this most beautiful of planets – most beautiful, that is, for those using a small telescope. I’m afraid Saturn’s rings are not within the reach of those using binoculars, and it’s the rings that make this planet so astonishing. Even when you know exactly what you will see, the 3-D impact of those rings going around the planet are a sight you will never forget, so if you get an opportunity to see Saturn in even the smallest telescope, do take that opportunity.

Finding Jupiter should not be an issue – simply look for the brightest “star” in the west southwest. The only real star you could confuse it with is Sirius – and Sirius will be dimmer and half a sky away in the southeast at that time. About an hour after sunset Jupiter will be about 30 degrees above the horizon – certainly easy to see and view with binoculars or a small telescope. But it sets about four hours after sunset and long before that it will become difficult to view. By the end of the month it will be about 13 degrees above the horizon an hour after sunset and will set in another hour or so. It will make a pretty sight in the southwestern twilight sky to the naked eye but will not be a good target for binoculars and telescopes when that low.

Saturn, however, is a good replacement, making another bright “star” for anyone to pick up with the naked eye and a wonderful sight for the small telescope user.

To find Saturn you need to wait until about six hours after sunset at the start of the month, then look south of east. By the end of the month this is the scene about four hours after sunset. Click image for larger view. Chart is for those in mid-northern latitudes. (Prepared from Starry Nights screen shot.)

To find Saturn you look east about six hours after sunset at the start of the month – four hours by the end of the month. To the north of east you should see brilliant Arcturus rising and a bit higher than Saturn. It also is about half a magnitude brighter. Saturn will have a slight yellowish cast and be a bit south of east. The two will be the brightest stars in that section of sky at the time, although in less than an hour they will be joined by Spica, a bit dimmer than Saturn and just below it.

Venus continues to dominate the morning sky to the southeast, but it is starting to get close to the Sun. It rises about three hours before the Sun at the start of the month – two hours before sunrise by the end of the month. Can’t be missed, though. At magnitude -4.2 it’s about twice as bright as Jupiter and will be outshone only by the Moon and the Sun. On February 28 and March 1, Venus will make a nice pairing with the waning, crescent Moon.

 

Basking in the Zodiacal Light of Almost Spring

The last 10 days or so of February 2011 will be a good time to start looking for that most elusive of Solar System sights, the Zodiacal Light.

Now this is something much different. You don’t need a totally clear horizon to see the zodiacal light, or binoculars, but you do need total darkness and that means little-to-no light pollution and no Moon. So you want to wait until a few days after full Moon to begin this quest. I feel I have a good shot at it from my favorite ocean-front observing point where I have a clear horizon to the west with no cities to create light domes there. Evenings in February and March – and mornings in September and October – are the best time for folks at mid-northern latitudes to look for this.

The zodiacal light is roughly the same intensity as the Milky Way, so if you can see the Milky Way from your chosen location, then you should be able to pick up this faint glow. Like the Milky Way, it stretches over a good deal of sky. It is widest near the horizon and gets narrower as it rises towards the zenith. You want to look for this roughly 80 minutes after sunset. You can check for an exact time for your location by getting information from here on when astronomical twilight ends. (The drop-down menu on that page specifies the times for astronomical twilight.) As astronomical twilight ends you want to start looking. As with any faint object, your eyes need to be dark adapted, so I am assuming you have been out for at least 15 minutes with no white light to dazzle you. If you try to look for this earlier, you may confuse it with twilight. Much later and it is not as bright, for what we are seeing is sunlight reflecting off interplanetary dust particles – dust particles that orbit in the same plane as the planets – the area we call the zodiac – and thus the name for this phenomena, zodiacal light.

If you see it, reflect on this explanation from Wikipedia:

The material producing the zodiacal light is located in a lens-shaped volume of space centered on the Sun and extending well out beyond the orbit of Earth. This material is known as the interplanetary dust cloud. Since most of the material is located near the plane of the Solar System, the zodiacal light is seen along the ecliptic. The amount of material needed to produce the observed zodiacal light is amazingly small. If it were in the form of 1 mm particles, each with the same albedo (reflecting power) as Earth’s Moon, each particle would be 8 km from its neighbors.

For the metrically-challenged (that includes me) that means one dust particle every five miles! And that causes all that light?! Awesome!

 

Algol takes a Dip, or Two, or Three

I wrote about Algol the “Demon Star” in the posting for October, but it’ s still well placed for viewing in February, and if you look at the right time, you’ll catch it in mid-eclipse, which is cool.

Every 2.3 days Algol dims like clockwork, but it is only at its dimmest for about two hours, so to see it in this condition you really need to be watching at the right two hours. Fortunately, there are several places that will give you a list of times when this occurs – but many of them will be while normal people are sleeping – and many more will be during daylight hours. However, each month there should be one or two dates when it is really a good time for you to catch Algol doing its thing.

Most of the listings I know of for Algol “minima” give date and time in Universal Time. What I like about the one at Sky and Telescope magazine, is it will calculate a list of coming Algol minima for you – and give you the Universal Time, plus your local time. So it’s easy to glance over it and see when it will be most convenient – weather permitting – for you to take a look. In my case, February 2011 gives me a couple of opportunities worth noting:

  • 02/09/2011 @ 10:18 pm
  • 02/12/2011 @ 07:07 pm
  • 03/04/2011 @ 08:53 pm

Yes, that last one is for March, but why not plan ahead a little – with winter weather it’s easy to get clouded out, so the more opportunities the better your chance of seeing something. I find these eclipses amazingly elusive and rarely see one, maybe because I think there’s always going to be another opportunity.

 

Also new this month:

Prime Time observing for October 2009

Seeing a bow, a demon,  and a few hundred billion stars  – meanwhile, Jupiter slams it into forward!

Please note: All charts with this post are for observers in mid-nothern latitudes centered on 40° N. If you are 10 or more degrees south or north of that – or if you’re not sure of your latitude – please go here to make your own custom star charts.

On tap this month is a new asterism,  the bow; a variable, Algol, the “demon star;” a neighboring galaxy you can see with the naked eye or binoculars; and yes, Jupiter, which appears to abruptly change directions as it moves against the background stars.

To begin our monthly exploration of the night sky, you can take a slide down Andromeda’s Couch to Mirfak and the Bow of Perseus in the northeast, assuming you learned these last month. If these are new to you, simply start by looking for the rising low in the northeast.

As usual, go out 45 minutes after sunset and watch the stars emerge. It may take another 15 minutes for  to see the bow  clearly, but what you are looking for is three stars in a vertical arc, with the middle one – Mirfak –  the brightest. How big an arc are we talking about? Just make a fist and hold it vertically at arm’s length, and your fist should just cover these three stars. How high? The bottom one should be about a first above the horizon.  Here’s a chart modified from Starry Nights Pro software..

Click chart for much larger view. If you observed last month you know the Great Square and Andromeda's Couch and can slide down the "Couch" to Mirfak, the brightest star in the bow of Hercules. If this is your first month of learning the sky, simply look to the northeast and find the bow.

Click chart for much larger view. If you observed last month you know the Great Square and Andromeda's Couch and can slide down the "Couch" to Mirfak, the brightest star in the bow of Perseus. If this is your first month of learning the sky, simply look to the northeast and find the bow.

Now if you want to be a stickler about mythology, Perseus doesn’t carry a bow – he wields a sword instead, which he is holding in his right hand high over his head, while in the left hand he holds the severed head of Medusa. Here’s how the 1822 “Urania’s Mirror” depicted it.

perseus

Perseus - click for alarger version.

Oh boy – and if you can see all that in these stars, then you have a very vivid imagination. I never would have learned the night sky if I had to try to trace out these complex constellations as imagined by ancient cultures and depicted in star guides up until fairly recently.  And for the purposes of helping you find your way around the night sky I think remembering the Bow of Perseus is easier. Mirfak, is just a tad dim to serve as one of our guidepost stars, but it does come in handy when identifying the “Demon Star,” whose proper name is Algol.

Getting sharp about brightness

As you start to learn the stars, it may surprise you how precise you can be about their brightness.  At first you may have difficulty just telling a first magnitude star from a second, but if you get to know Algol, the “Demon Star,” I bet you’ll find that you can quickly become quite sophisticated in assessing brightness and shaving your estimates down to a tenth of a magnitude.

Imagine a star that regularly varies in brightness every few days – that’s what Algol does. Exactly every 2 days, 20 hours and 49 minutes it begins a 10 hour period where its brightness dims more than a full magnitude. If you look during the right two hours, you’ll catch it at or near its dimmest – and most of the rest of the time you’ll catch it at peak brightness. And it’s quite easy to judge. But first let’s find it. Here’s the chart we’ll use.

algol_no_mags_web

Notice how Algol makes a very nice triangle with two companions, and all three stars are close to the same brightness – Almach, the bottom star in Andromeda’s Couch; Mirfak, the central star in the Bow of Perseus; and Algol. That brings us to our first challenge: Go out any clear night and study these three stars and decide which is the brightest. Two are equal in brightness, but one is a tad brighter than the other two. Which is it? Algol? Mirfak? Almach? (The answer is at the end of this text so you can ignore that answer until you actually have an opportunity to test yourself.)

However . . .

Because Algol is a variable, sometimes when you look at it, Algol will actually be significantly dimmer than either Mirfak or Almach. In fact, there’s a reasonable chance it will be dimmer than either of Mirfak’s two fainter companions that make up the Bow of Perseus. If when you test yourself, this is the case, congratulations! Make note of the date and time.

Algol is a special kind of variable star known as an eclipsing binary. That is, what looks like one star to us is really two stars, and when we see Algol’s light start to dim it means its companion is passing between Algol and us causing an eclipse. Since the stars are locked in orbit around one another this happens with clockwork regularity.

algol_edu

The above diagram came from this astronomy class web site which includes amore detailed scientific explanation.

Since either star of the pair can cause an eclipse, there is a much fainter, secondary eclipse of Algol – really too faint to be noticed by most observers. Why is one eclipse fainter – because one star is blue, Class B – and much hotter/brighter than the other star which is “K” class. (Remember – OBAFGKM.)  It is when the cooler star is in front that we see the dramatic change in light.

It’s fun to catch Algol in mid eclipse, but I suggest you not read about when to do this right now. Instead, do the little challenge first. Then when you’re ready, go to the final item in this, which explains how and when to catch Algol in eclipse and in the process, tells you the brightness of its companions.

OK – second project – Jupiter changes direction!

I described this in an earlier post an am quotingit in its entirety here.

On October 1, 2009 a nearly full moon joins Jupiter, Uranus, and Neptune in the southeast as shown here about an hour after sunset as seen from latitude 42 degrees north and longitude 71 degrees west. Chart from StrayyN oghts Pro software. Click for larger image.  .
On October 1, 2009 a nearly full moon joins Jupiter, Uranus, and Neptune in the southeast as shown here about an hour after sunset. (Jupiter is made large to indicate its relative brightness – ut it will look like a very bright star – not a small moon!) This is how the sky appears from latitude 42 degrees north and longitude 71 degrees west. Chart from Starry Nights Pro software. Click for larger image.

The idea here is simple – connect what we can see in the sky this month with what’s actually going on. We’ll do this by watching Jupiter, the easiest object to find right now since it is the brightest “star” fairly high in the southeast shortly after sunset.

With just a few quick checks with binoculars we should be able to track the movement of Jupiter in relation to a bright, nearby star. You should start this project on or before October 1, 2009 if at all possible and plan to observe two or more nights between your start time and October 13. Then observe again in about a week and again near the end of the month.Your first couple of checks should show Jupiter in “retrograde” moving westward among the background stars. Your next two checks should show Juputer has resumed it’s normal eastward movement.

Use the following chart as both your guide and your log. That is, click on it to get a version you can print, take out under the stars, and record your observations on with a pencil.

Click for larger version, suitable for printing.
Click for larger version, suitable for printing.

So why does Jupiter appear to first go one way, then the other? Afterall, it isn’t really doing that, is it? Like the other planets – and us – it’s simply continuing a steady, eastward journey around the Sun. But so are we – and we are moving much faster because we’re much closer to the Sun. So what you are seeing is partly the movement of Jupiter – but also the apparent change in its position caused by our rapidly changing position.

I made the following animation from Solar System Live charts. It shows how Jupiter’s position changes slowly in relation to Earth and the other planets, particularly Neptune. The animation starts with September 1, 2009  and moves a month at a time for six months. The arrow shows our changing view of Jupiter with relation to Neptune, a much more distant – and even more slowly moving, planet. Notice that in late December Jupiter makes another close approach to Neptune – the third this year – which will make especially easy at that time to find this distant and faint planet. Right now you can use the chart above to track it down – it would be just visible in binoculars on a moonless night.

picasion.com_8320c15f05e4065bb6a5159017c4c205

So let’s review the movements we’re dealing with here.

1. The daily rotation of the Earth causes Jupiter to appear to rise inthe east and move westward as the night progresses.

2. The revolution of the Eartha round the sun at a much higher speed than Jupiter makes it so that for some time the huge planet appears to be moving westward in relation to background stars and the more distant planet Jupiter. That apparent westward motion comes to a stop October 13, 2009.

3. Jupiter’s own motion is more apparent after October 13, as it appears to move eastward against the background stars. This general motion will carry it about 30 degrees eastward – very close to where Uranus can be found now – in about a year. It takes Jupiter almost 12 of our years to make a complete circuit of the sky.

The idea here is simple – connect what we can see in the sky this month with what’s actually going on. We’ll do this by watching Jupiter, the easiest object to find right now since it is the brightest “star” fairly high in the southeast shortly after sunset.

See a few hundred billion stars at one glance!

Yes, you can do it if you have good dark skies, you have allowed your eyes to dark adapt, and you are looking at the right place.  Once again, Andromeda’s Couch is our guide, and what we are looking for this time is the Great Andromeda Galaxy aka M31.

This is our “neighbor” in space if you can wrap your mind around the idea that something “just” 2.5 million light years away is a “neighbor.” ( As you try to do that remind yourself that a single light year is about 6 trillion miles – of course, good luck if you can imagine a trillion of anything!)

But seriously, you can see this with  your naked eye – and even in normal, light-polluted skies, you can see it with binoculars. In fact, this is one object where the binocular view can be almost as rewarding as the view through a telescope. Here’s a wide field chart for mid-month and about 90 minutes after sunset. At that point the galaxy should be roughly half way up your eastern sky.

m31_finder

Click image for larger version.

Starting with the preceding chart – and moving to the chart below:

  1. Locate the Great Square
  2. Locate Andromeda’s Couch off the northeast corner of the Square.
  3. Go down to the middle star in the couch, then count up two stars and bingo!
  4. You can also find the general vicinity by using the western end of the “W” of Cassiopeia as if it were a huge arrow head pointing right at the Andromeda Galaxy.
Click image for larger chart.

Click image for larger chart.

Well, “bingo” if you have been doing this with binoculars. With the naked eye it’s more an “oh yeah – I see it – I think!” But what do you expect? Think about it. The light from the near side of this object started its journey about 150,000 years before the light from the more distant side did! And think of where the human race was 2.5 million years ago when these photons began their journey – or for that matter, where all these stars really are today! Nothing is really standing still -everything is in motion.

You might also want to think about the folks who are on a planet orbiting one of those stars in the Andromeda Galaxy and looking off in our direction. What will they see? A very faint patch – probably fainter than what we see when we look at the Andromeda Galaxy, but in binoculars and telescopes roughly similar in size and shape.  Both Andromeda and the Milky Way Galaxy we inhabit are huge conglomerations of stars. We’re about 100,000 light years in diameter – Andromeda is about 150,000 light years in diameter. The Milky Way contains perhaps 100 billion stars – the Andromeda Galaxy maybe 300 billion.  (Don’t quibble over the numbers – even the best estimates are just estimates. )

And yes, in a few billion years we will probably “collide” with the Andromeda Galaxy, for we are hurtling towards one another. Such galaxy collisions are not that unusual  and probably aren’t as violent as the word “collision” makes them sound – but they do, in slow motion, bring about radical changes.

But all that is for the professional astronomers to concern themselves with – for us, there’s the simple beauty and awe of knowing that with our naked eye – or modest binoculars – we can let the ancient photons from hundreds of billions of stars ping our brains after a journey of millions of years.

And now the truth about Algol and companions

Have you done the Algol test yet? Looked at Algol, Mirfak, and Almach and tried to decide which is brightest? If so, you can check your answer by continuing to read. If not, I suggest you first do that exercise, then come back to this.

Chances are that when you look at Algol, it will be at its brightest – but how can you tell? Well, as we mentioned, you can compare it to Mirfak – but there’s an even closer match with another nearby bright star – Almach.  That’s the third star in Andromeda’s Couch  – the one neareast Algol.

Mirfak is the brightest of the three at magnitude 1.8.

Almach is magnitude 2.1 – the exact brightness of Algol when Algol is at its brightest – which is most of the time. OK – for the hair splitters, Almach is a tad dimmer, but the difference is far too little to be able to tell with your eye.

Here’s a chart showing the magnitude of the stars near Algol that you can use to compare it to and see if it is going through an eclipse.  People who look at variable stars use charts like this, but with one important exception – the numbers are given like they were whole numbers so you will not confuse a decimal point with another star. Thus, a star like Mirfak, of magnitude 1.8, would have the number “18” next to it. I broke a convention here because there are just a few bright stars on the chart, so I didn’t worry about the possible confusion of a decimal point being another star.

algol_mag_color

So If Algol and Almach are the same, no eclipse is going on at the moment.  If Algol appears dimmer than Almach, then an eclipse is in progress. If it’s as dim or dimmer than either of the companions of Mirfak in the Bow, then you can be pretty sure you’ve caught Algol at or near  its darkest. In two hours – or less – it will start to brighten and will return to full brightness fairly quickly.

Catching Almach at its dimmest is fun, but not as easy as it may seem. Why? Because although  an eclipse happens every few days, it may happen during the daylight hours, or in the early morning, or some other time when it’s inconvenient. And, of course, you need clear skies.  So when I want to observe an Algol eclipse, I go to a handy predicting tool on the Web that you can find here.

I then note the dates and times and pick out only those dates when the times are convenient to me – that is, happening during my early evening observing sessions. Then, given the  iffiness of the weather, I usually find that there are only one or two times a month when I’ll get a good look at an eclipse of Algol.

If I do this for October I find that out of 11 Algol minima, just three hit at the right time for me. Those dates and times are:

  • 10/01/2009  9:09 pm EDT
  • 10/21/2009  10:50 pm EDT
  • 10/24/2009  07:39 pm EDT

Of course the dates and time may be different for you, depending on where you live, and none of us can escape the whims of the weather! So here’s hoping for clear skies for you so you can find a winking demon, follow the actions of Jupiter, and capture in your own eye the photos from a few hundred billion stars in the Andromeda Galaxy!

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