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 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.
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!
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.
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!
"I must go down to the seas again, to the lonely sea and the sky, And all I ask is a tall ship and a star to steer her by..." John Masefield, 'Sea Fever' (1902) You might not realize it while looking at the stars with your naked eye, but stars are constantly moving across the sky. This is because of the Earth's rotation along its North-South axis, which makes relatively stationary stars in the night sky appear to move slowly in a circular fashion. So it's not so much the stars moving - it's you who's moving! This movement can be clearly seen if you have a magnified look at a star with a fixed telescope or pair of binoculars - the star will appear to travel slowly across your field of view in the eyepiece. A good demonstration of this can be seen in my video below, taken in real time through my telescope, of Procyon, in the constellation Canis Minor.
Note that Procyon is actually a binary star system, consisting of a bright white main sequence star named Procyon A and a faint white dwarf companion named Procyon B, the very much fainter star which you can just about see to the left of Procyon A in the video above. However, both stars can clearly be seen to be travelling slowly across the sky from left to right in the video above. There is, however, one star among the thousands that you'll be able to see in the night sky that does NOT seem to move at all. This is Polaris, in the constellation Ursa Minor, and a clue as to why this star does not seem to move at all is in the name. Polaris is a short form of the Latin 'stella polaris', which means "pole star". The star lies nearly in a direct line with the North-South axis of the Earth's rotation and, as a result, appears to stand almost motionless in the sky, as the Earth and all the stars of the Northern sky appear to rotate around it. And if you don't believe me, below is a video of Polaris, taken on the same night as the video of Procyon above, using the same telescope and video settings and captured in real time as well. You can see that Polaris hardly moves at all.
An even clearer demonstration of this effect are star trails. If you were to point your camera at Polaris and take a large number of long-exposure photographs (varying from 30-second to 10-minute exposures, depending on lighting conditions and your camera's capabilities) and combine them into a single image, the photo below will be the result - the motion of the stars leaving a trail ofcircles across the night sky, with the motionless Polaris at the centre of these concentric circles.
Because of this unique position that Polaris is in, the star used to be crucial in the old days of naval navigation by the stars. The navigator only needs to find Polaris to find which direction is North. And Polaris is easy to find - even on a cloudy, light-polluted sky, as in the picture on the right. Just locate the two stars that form the outer edge of the 'bowl' of the Big Dipper (called the Plough here in England but I prefer to refer to it as the Saucepan!) Draw an imaginary line straight through the two stars of the dipper edge and the first star it hits of about the same brightness would be Polaris. In addition, because the star is so far away from Earth (434 light-years), the angle from the horizon to Polaris is the same as the latitude. This angle can be measured precisely using a sextant. Once the latitude is known, all that is then required is to find the longitude. Unfortunately, finding longitude is a bit more complicated - it relies on noting the time at which other stars rise, set, or reach a known position in the sky.
Among my prized possessions in the living room are a brass sextant, naval compass and pocket chronometer (see picture on the left). So, if the Sat Nav, GPS or tom-tom in the car should go on the blink one clear dark night, the only things I'd need would be my trusty sextant and chronometer - and, of course, a star to steer her by!
It is not by accident that my observations over the past few weeks were focussed on the Lyra constellation. I was doing this to familiarise myself with that area of the sky surrounding Lyra, primarily because this weekend is the peak of the Lyrids meteor shower - so called because the meteors would be observed radiating from this constellation. The source of this meteor shower are particles of dust shed in the cometary tail generated by the periodic Comet C/1861 G1 Thatcher. The Lyrids normally yield an average of ten meteors per hour at its peak, so this is hardly the spectacular light show that you would see from the Perseids in August, the Leonids in November and the Geminids in December - with these you could probably see at least one meteor every minute. However, the Lybrids can produce meteors known as "Lyrid fireballs", which are significantly brighter and more spectacular than the thin streaks left by other meteor showers and may even leave behind smokey debris trails that last minutes. I managed to capture my first ever fireball on camera last night:
The good news for those of you interested in meteor-hunting is that you don't need a telescope to do it. You just sit back in your lawn chair and look up to the sky with your MK I eyeballs. While meteors appear to radiate from one point in the sky (called the radiant), they can appear anywhere in the sky and at any time point in time - so a telescope would be virtually useless because you would have no idea where to point it. The bad news is this also means you have no idea where to point the camera at and makes meteors very, very difficult to photograph well. So what I had to was to point the camera at about 45 degrees to one side of the radiant, set it at a wide field of view, have the camera automatically take time lapse photographs of 15-second exposures for two hours and hope for the best. That one photograph above was from over 200 images taken. What's even more frustrating is that I managed to see at least one other fireball that was even more spectacular - it had much longer fire trail and lit the sky around it with a fiery green glow that lasted a full two seconds at least. Unfortunately, my camera was pointed in exactly the opposite direction during those two seconds. Of course, taking time lapse photographs will also unintentionally capture every flying object in the sky, not just meteors. This includes the object below - not a Constitution-class Federation starship or a Klingon Bird or Prey, unfortunately, but a normal commercial passenger plane, judging from the regular patterns made by the red and yellow navigation lights and beacons.
Another challenge in meteor hunting is, of course, the British weather. Considerting this green and pleasant land has such horrid and unpleasant weather, I think it is nothing short of a miracle that this country can produce astronomers the likes of Isaac Newton and Edmond Halley. Last night was absolutely blanketed in cloud, the image below being typical of what conditions were like. Very pretty, of course, but very frustrating astronomically. I essentially only had a small windows of less than half an hour of a decent amount of clear sky to capture any images.
Nevertheless, last night was a good dress rehearsal for the big light show coming up in August - the Perseids. Here are a few tips on how you too can go meteor hunting then:
Check for the peak time of the meteor shower.
Meteors will tend to cluster around a single point in the sky called the radiant. Aim your camera toward this point, but not directly at it - about 45 degrees to one side will give you the highest chance of catching the most meteors and you'll be able to capture as much of the meteor trail as possible.
Use a sturdy tripod and remote shutter trigger or shutter release cable, if available, to eliminate camera shake. You could also use the self-timer. Ideally, you should have a camera or camera control computer software that would allow time lapse photographs to be taken automatically.
Use the manual mode on the camera to have full control
Set to a wide angle setting - this increases your likelihood of success. The wider your lens, the more sky you'll get in your photo and the higher the chance you'll catch a shooting star. But not too wide though - otherwise your meteor streak will appear too small and quite unimpressive.
Use manual focus. Focusing on stars can be difficult in a dim viewfinder, so set the focus by focussing on a bright star such as Vega or Arcturus, or just set it to infinity.
Set F stop settings just short of wide open
Set cameras for long shutter times but not too long, to avoid star streaking and CCD noise.
Lots of short 5-15 second exposures might do better than, say, a single maximum exposure, since long exposures with digital cameras result in noisy images My shot above was taken using 15-second exposures.
Meteors are impossible to predict, and it takes a great deal of luck to capture them on digital film. Don't be discouraged if you take a hundred photos of the empty sky - if you keep trying, eventually you'll catch that one beautiful falling star!
Bring a lawn chair and sit back to enjoy the show.
