In the shadow of the Terminator

You might think that the best time to observe the moon is when it is at it's brightest - during the full moon. Actually, that's probably the worst time to see the moon. When the moon is full, it tends to be dazzlingly bright as well as flat and one-dimensional in appearance. All the detail of craters, mountains and valleys will be completely washed out by the dazzling light. In contrast, the interval when the moon is at or just past first quarter phase, or at or just before last quarter phase, is when we get the best views of the lunar landscape - and the best views can be seen right along the sunrise-sunset line, or terminator - the line between the illuminated portion and the part of the moon in shadow.)

 Just looking at the image of the moon above, you can see that the topographies of the northern and southern hemispheres of the moon are quite different. The top half consists mostly of the lunar plains called maria (singular mare), the Latin for seas. They got this name from early astronomers who mistook their wide, dry, airless expanses for earthly seas - they are actually large, dark, basaltic plains, formed by ancient volcanic eruptions. There are also a few craters which are small and circular. However, as you move south to the bottom half of the moon, it gets lighter in color, and will consist mostly highlands, covered with many more large, complex craters. 

Let's start with this image of the northern pole of the moon below.

You'll see a few small, round craters, such as Democritus and Galle. Democritus is only about 25 miles in diameter, while Galle is about 21 km wide. Both craters are nearly circular, with sharp-edged rims and little appearance of erosion. They are located in a wide plain known as Mare Frigoris (the "Sea of Cold"). However, southeast of Galle, in the shadow of the terminator, you will just about see a much larger crater, Aristoteles. This crater is 87 km in diameter and the small crater on the right immediately under Aristoteles is Mitchell. An arc of mountains separate these craters.

Head a little further south in the northern hemisphere and you'll see two very interesting craters below.

Ritter, at the bottom of the image above, is a lunar crater located near the southwestern edge of Mare Tranquillitatis (Sea of Tranquility). It is the northwestern member of a crater pair with Sabine to the southeast. The two rims are separated by a narrow valley only a couple of kilometers wide. The Sea of Tranquility is actually quite special because it was the landing site for the first manned landing on the Moon - the area just to the east of Ritter and Sabine. After making a smooth touchdown in the Apollo 11 Lunar Module named Eagle, astronaut Neil Armstrong told flight controllers on Earth, "Houston, Tranquility Base here. The Eagle has landed." 

Another interesting feature in the image above is Plinius - a prominent lunar impact crater on the border between Mare Serenitatis (Sea of Serenity) to the north and Sea of Tranquility to the south. If you look carefully at this crater, you might be able to make out a central peak right in the middle of the crater floor. This centrla peak is more evident in the zoomed image of Plinius below.

How was this central peak formed? Well, if you drop something into a pool of water, you will get a rebound effect in the middle where the object was dropped, and then waves will spread out around it. This rebound effect in the middle is the same phenomenon that causes central peaks in craters. the central peaks are formed by rock rebounding, being pushed back up by the strength of the underlying rock after the initial impact event. An impact that forms a crater on the moon that is greater than 15km will cause the rock to act like the liquid to the point that you get the rebound effect and form a central peak. Smaller craters  will not have central peaks, and larger craters above 120 km will form a ring of peaks. Central peak formation happens within minutes of the impact itself. 

Head further south into the southern hemisphere and you will more clearly see more of these central peaks in the image below. 

Theophilus is a prominent lunar impact crater that lies between Sinus Asperitatis (Bay of Roughness) in the north and Mare Nectaris (Sea of Nectar) to the southeast. It partially intrudes into the comparably sized crater Cyrillus to the southwest. To the east is the smaller crater Mädler. The floor of the Theophilus is relatively flat, and it has a large, imposing central peak which is 1,400 meters high.

And as you head to the southern pole, you'll see the basalt plains make  way for more rugged highlands that are pock-marked by hundreds of craters - indicating that this part of the moon once endured some heavy battering at one time in the very distant past.

All photographs on this page  © Sabri Zain 2012.

Colliding Galaxies

If someone were to ask you how far you would be able to see with the naked eye unaided, what would your answer be? A couple of miles, at best? Well, the answer is actually 14,696,563,432,959,020,000 miles - that's 14.7 quintillion miles. This is because it is possible for anyone to see, with the unaided eye and without the use of a telescope or binoculars, our nearest neighbour galaxy - the Andromeda Galaxy, which is about 2.5 million light years from us.

Now, it would have to be a really clear, dark, moonless sky for you to see it. And even then, all you'd probably see would be a faint smudge. Even with a small telescope such as mine, you'd be able to make out it's shape but it would still appear as a fuzzy white patch in the sky. But just the thought that you are looking at a patch of light that took two and a half million years to reach you and is many quintillion miles away - well, that just blows my mind! And you're not just looking at another planet or star - that is a whole new galaxy, just like our own Milky Way! Below is a photograph I took of Andromeda last night, over the northeastern skies of Longstanton - my first photo of a galaxy! It;s that fuzzy cloudy 'star' near the centre of the picture.

While the Andromeda Galaxy is pretty easy to see in a telescope, because it is just a fuzzy patch, taking the photograph above was deuce difficult. CCD cameras for small telescopes are also called lunar planetary imagers - which means they're primarily designed to capture images of the moon and a few planets. To capture stars, they'd have to be pretty bright - at least magnitude 5 or less. So fuzzy patches would be impossible. I had to use my Olympus Camedia C4040Z digital camera afocally with the eyepiece. To get decent pictures of fuzzy deep sky objects with a camera, you'd need long exposures - typically, at least a few minutes. My ancient C4040Z unfortunately has a maximum exposure time of just 16 seconds. To make up for the lack of long exposures, I squeezed as much wide aperture as I could out of the camera (1.8) and used the maximum ASA available (400). There was quite a bright crescent moon out as well, and I was observing about an hour before dawn, so seeing conditions were far from ideal.

Now, if I had a telescope such as the WIYN 0.9-meter telescope at the Kitt Peak National Observatory in Arizona, I would not need all the fuffing about with exposures, apertures and film speeds. The picture of the Andromeda Gakaxy below was taken by the WIYN 0.9-meter telescope. And just to give you some perspective of the size of that - that telescope's 12 times bigger than mine, has banks of CCD imagers built into it and cost half a million US dollars!

Andromeda is not only the closest galaxy to the Milky Way - it's also moving closer to us every day! Andromeda and our Milky Way are hurtling towards each other at about 70 miles per second. But before you have sleepless nights fretting about alien suns and planets crashing into your garden shed one night,   astronomers estimate that this galactic collision with Andromeda will probably take place about 5 billion years from now. By that time, our Sun would have swollen into a red giant and swallowed up the inner Solar System planets, so Earth will have other things to worry about!

Non-lunar Phases

Clear skies at last this evening  and here is my latest image capture as twilight descended over Longstanton. After the excitement worldwide over the 'Supermoon' of last week, those of you who read my bLog about it might think that the photograph above is yet another amateur photograph of the perigee full moon. However, the 'supermoon' ended days ago and the more observant among you might note that this is not a full moon but a crescent. You might also happen to notice that it has a brownish-red hue - not the familiar cheesy white of our moon. This is, in fact, not a moon at all but a planet - the rock just before us, Venus.

If you had been looking above the skies of Cambridge this evening, you wouldn't have seen this crescent at all - you would have seen what appears to be a very bright star very low on the horizon, to the west. It is so bright, in fact, you would probably have seen it in the daytime (as in my picture below) rather than during darkness, as it rapidly descends below the horizon quite early in the night this time of the year.

What most non-astronomers don't know is that Venus also experiences phases, similar to the lunar phases of our moon. The phases of Venus result from the planet's orbit around the Sun inside the Earth's orbit, giving the telescopic observer a sequence of progressive lighting similar in appearance to the moon's phases. It presents a full image when it is on the opposite side of the Sun. It shows a quarter phase when it is at its maximum elongation from the Sun. Venus presents a thin crescent in telescopic views as it comes around to the near side between the Earth and the Sun (as it does in the picture above and in my video below) and presents its new phase when it is between the Earth and the Sun. The full cycle from new to full to new again takes 584 days (the time it takes Venus to overtake the Earth in its orbit). 

You might have noticed a shimmering effect in the video, especially as Venus descended down to the horizon. - this effect is caused by heat currents from the roofs of houses. This is particularly a problem when viewing or video capturing celestial bodies that are found close to the horizon. The problem becomes markedly worse when you're viewing at high magnifications and through Barlow lenses (here, I used a 2X Barlow with a Celestron Neximage CCD imager equivalent to a high-power 6mm eyepiece).

Photographs taken of the Venusian surface by NASA probes do show a reddish colouration of the surface rocks, which could be oxidized iron compounds. However, the reddish colour you see in my photograph above is not Venus' true colour - Venus usually appears a very light gray or tan when viewed from Earth (see a second video I took below - this time without using the Barlow lens). 

The red in the photo is probably due to light pollution from the street lights on Magdalene Close affecting my optics (see the picture above). 

Light Pollution is, in fact, a constant frustration to every amateur astronomer who lives under the overpowering glare of suburban lighting. So to those of you who have those piercing security lights that light up half the village - please give a thought to your poor neighbourhood astronomer, shivering in the cold of the night, fumbling with his knobs and cursing under his breath because the flippin' glare is spoiling his view of Venus ...!

All photographs on this page  © Sabri Zain 2012.

Monster sunspot

The cloudy weather we've been having here in Cambridge these past few weeks have masked the fact that, for the past week, we have been experiencing probably the most powerful series of solar flares from the Sun this year. NASA has classed these as M-class solar flares - medium-strength sun storms that can unleash powerful blasts of radiation and magnetic solar plasma. The source of these solar flares are what NASA have dubbed "a monster sunspot" - a huge sunspot 60,000 miles in width which NASA have designated Sunspot AR 1476. This Saturday was the first really clear day this month, so I dusted the cobwebs off my long-neglected refractor and pointed her at the sun. This is what I saw:

Sunspot AR 1476 is that smudge a little off-centre on the left limb of the Sun. Now, it may well look like just a little smudge but bear in mind that it's at least 60,000 miles long - that's 8 times the diameter of the planet Earth!

Increasing the magnification of the scope with the equivalent of a 6mm eyepiece reveals a little more of the sunspot. The dark core (umbra) surrounded by a larger lighter filamentary outer region (penumbra) are clearly visible.

Increase the magnification with a 2X Barlow even more and you'll see that there are about half a dozen smaller dark penumbrae radiating around the central core.

On the scale of solar flares, the M-class storms produced by AR 1476 are the second-most powerful flares and can set off geomagnetic storms that create dazzling northern lights displays when the eruptions reach Earth. X-class storms are the most powerful on the scale and can interfere with satellites and infrastructure such as electrical power transmission on Earth when aimed at our planet. But don't worry - the flares are apparently short-lived and not expected to disrupt satellite communications or take down power lines, so you should be able to enjoy your daily fix of Coronation Street and East Enders uninterrupted.

The sun is currently in an active phase of its 11-year solar weather cycle. The current cycle, known as Solar Cycle 24, will peak in 2013. So you still have another year to get yourself a telescope and a solar filter and enjoy the breath-taking sight of deadly solar radiation and plasma spewing millions of miles straight towards you!

All photographs on this page  © Sabri Zain 2012.

Meet the new addition to the family!

It's finally arrived this week - a big brother for my little 80mm Meade ETX-80 refracting telescope, my new Meade 114EQ-AR reflecting telescope! Well, I say 'new' but it's actually a second-hand scope which I bought off eBay for the princely sum of 40 English pounds. Which is not a bad deal, considering these things are retailing around the £200-£300 mark. Just goes to show that astronomy doesn't have to empty your bank account.


Okay - the details! The Meade 114EQ-AR is a long-tube equatorial reflector with a 114mm aperture and 900mm focal length (f/8). It houses an overcoated primary mirror, rack-and-pinion focuser and is borne on a heavy  German Equatorial Mount with covered worm gear slow-motion controls, setting circles and latitude control with scale. Don't run away yet - I'll explain some of this technobabble to you later on.

But the big question (certainly from my wife) - what on planet Earth would I possibly want with two telescopes? Well,  the 114EQ-AR is in many ways quite a different telescope from my ETX-80.


Firstly, the "114" in the name indicates that it has an aperture diameter of 114mm, or four and a half inches, which means it has much more light-gathering power than the three-inch objective lens on my ETX-80. Just compare the diameter of the 114EQ-AR on the right with ETX-80 on the left in the picture below. And more light-gathering power means fainter objects - such as galaxies, nebulae and planetary detail - will appear somewhat brighter.

Secondly, the Meade 114EQ-AR also works differently from the ETX-80. My old ETX-80 is a refractor - the type most people associate with how telescopes work - light goes in through a lens at the top and is focussed into an eyepiece at the other end which you look through. The 114EQ-AR is a classic Newtonian reflector - named after that other Cambridge stargazer.  Light enters at the top and hits a spherical mirror at the bottom, where it is reflected to a smaller mirror and eyepiece at the top. Looking at the picture above, you can see that the ETX-80 has an objective lens at the top, while the 114EQ-AR doesn't. You can also see that 114EQ-AR has a mirror at the bottom and its eyepiece is at the top rather than bottom. 


What difference does all of this make? Well, this means that 114EQ-AR has a longer focal length, which allows for higher magnifications, while the shorter length of the ETX-80 will tend to give wider fields of view. There is one big disadvantage to the set-up of a reflector, however - if you are a five-year old. Because it uses a long tube and the eyepiece is at the top, you won't be able to reach up to the eyepiece to have a look-see - even if you stand on your tippitoes on top of a foot stool!

The other big difference between the ETX-80 and my new 114EQ-AR is the mount. My old ETX-80 has a simple Altitude-Azimuth mount, that is, you move the telescope tube up or down vertically and left or right horizontally to position it to your target. The 114EQ-AR, on the other hand, has what's called a German Equatorial Mount (GEM). You don't move the telescope horizontally and vertically but move it along the polar and equatorial axes of whatever latitude you are situated at. (For more about polar axes, see my bLog entry on Polaris). So you can see in the picture on the right that the telescope itself is tilted to about  52 degrees - the latitude position of my observing site, sunny Longstanton. The setting circles shown in the picture below then allow me to accurately position the telescope to whatever longitude my target is located at.

The big advantage of a GEM for me is in photographing and video capturing my targets. As you read in my blog on Polaris, stars move across your eyepiece's field of view along the polar axis and you have to constantly move your telescope up, down, left and right to keep your target in your field of view. But with your telescope polar aligned, you just need to use the slow motion knob below to keep the object in view along the longitudinal plane - it's already tilted at the right latitude so you don't have to worry about moving it up and down.


So there you have it - the new 114EQ-AR for longer exposures and more light-gathering power for photos of fainter objects such as nebulae, galaxies, star clusters and planetary detail and the old ETX-80 for rich star fields, pin-point stars and splitting binary stars. Two quite different telescopes, with different strengths and weaknesses - but I love 'em both the same!

Super-lunar corona

The day before was the night of the 'Supermoon' - a phenomenon, known as a perigee full moon, where the moon passes just 221,802 miles from Earth, about 15,300 miles closer than average, making it appear 14% larger and 30 per cent brighter in the night sky. Those of us in Longstanton, however, would have completely missed this stunning sight as the skies were completely blanketed in thick cloud. Probably for the best, as the perigee full moon has been blamed in folklore for disasters, madness and even people turning into werewolves. I was certainly foaming at the mouth and growling like a wolf all night, having set up my scope and camera and seeing nothing but wall-to-wall grey clouds from dusk to dawn. However, the clouds last night turned from villain to hero when they helped produced the magnificent sight below - the lunar corona. 

The lunar corona is produced by the diffraction of bright moonlight by the water droplets of clouds - in fact, in just the same way a rainbow is formed from sunshine in the daytime. The corona, however, consists of a central bright aureole and small number of concentric colored rings around the celestial object, with reddish colors usually occupying the outer part of a corona's ring. The colours seen in the corona last night, in fact, changed dramatically as the cloud formations being blown over the moonlight changed, as you can see from the animation below, consisting of a series half minute time lapse pictures I took of yesterday's lunar corona.

All photographs on this page  © Sabri Zain 2012.

Waiting for a supernova

If you recall seeing a very bright red star in the night sky last winter, like a glittering ruby, the likelihood is extremely high that what you saw was Betelgeuse - the bright top 'left' star in the constellation Orion. You can probably just about catch it in the early evening this time of the year, somewhere to the west, just before it sets below the horizon. And you'd probably not need a telescope to pick it out as the rich red hue of Betelgeuse is quite visible even to the naked eye.

On a telescope, the flashing red is even more evident, as seen in this video I took last winter, and in the single frame image I extracted from the video.

The reason that Betelgeuse is so red is because it is a red supergiant sun that is experiencing its final death throes. Betelgeuse (most people pronounce it 'Beetle-Juice', though Patrick Moore insists it's more like 'Bettle-Gerz') is one of the largest known stars and is probably at least the size of the orbits of Jupiter around the sun. That's a diameter about 700 times the size of our Sun or over 600 million miles. And the more massive a star, the shorter its lifespan. Red supergiants are the rock stars of the Universe - they live fast and die young. Astronomers think Betelegeuse is at the very end of its life and will go supernova soon.

You can imagine what size explosion something 700 times the size of our son will produce. A supernova is a titanic event that is among the most violent in the Universe. The Crab Nebula below was formed as the result of a sun going supernova (and the explosion was actually seen and documented by Arab, Chinese and Japanese astronomers in the year 1054). The nebula has a diameter of 11 light years (that's 700,000 times the distance between the Earth and the Sun) and it's still expanding today at a rate of about 1,500 kilometers per second. (This picture, by the way, is from the Hubble Space Telescope - not my puny 80mm refractor!)

So are we Earthlings going to be engulfed in seering heat, lethal gamma rays and deadly radioactive particles when Betelgeuse explodes any day now? Probably not.

For one thing, when I said that Betelgeuse is at the end of its life and will go supernova soon, "soon" in cosmic terms here may mean Betelgeuse might blow up tonight, or it might go boom 100,000 years from now or it might be a million years from now. Astronomers just aren't sure - a million years is a very short time in terms of a star's life span.

Another thing that may reassure you is that it may look very bright and close by but Betelgeuse is really quite far away. More than 600 light years away, in fact. That’s almost 4,000,000,000,000,000 miles. That's a long, long way away. And astronomers have estimated that a supernova would have to be within at least 50 light-years of Earth for it to harm us.

And. for all we know. Betelgeuse may well have already been blown to bits - and we still don't know about it. Betelgeuse is 600 light years away from us, which means it takes light 600 years to reach us from Betelgeuse. The Betelgeuse I saw in my scope is what Betelgeuse looked like 600 years ago - for all we know, it might no longer be there at this very moment!

While it may be harmless to Earth, a Betelgeuse supernova would be a breath-taking sight to see. Betelgeuse would brighten over the course of a fortnight until it would outshine the Moon. It would probably still be smaller in size than the moon and look like the picture below (compare that to my picture of the Orion constellation above). The supernova would also be visible during the day. It would stay at that brightness for a couple of months before dimming rapidly over a few days until it would not be visible to the naked eye (though a small nebula might result that could be viewed in a telescope).

Now, that would probably be the most astounding sight that any astronomer would behold in his or her lifetime. So every time I'm out observing, I almost always unconsciously give a quick glance to Betelgeuse, waiting for a supernova. Like I said earlier - you'll never know when it's going to happen.

And I really, really want  to see it go boom. Even if that means the complete obliteration of Betelgeusian civilization. Sorry!