Saturday, 17 August 2013

Meteors over Andromeda

The annual Perseids meteor shower peaked last Monday night/Tuesday morning and, unlike previous years, we were fortunate enough to not only have reasonably dark moonless skies but also, unusually for Britain, clear skies. So conditions were ideal for not only observing meteors but also photographing them. Like my first attempt last year, my set-up consisted of two Olympus Camedia C-4040Z cameras pointed on either side of the constellation Perseus - one pointing east towards the Andromeda constellation and the other pointed north towards Cassiopeia.

The two cameras took together took over 400 16-second exposure time-lapse pictures and I was able to capture the descent of at least three meteors - including the rare one below of a meteor cutting across the Andromeda Galaxy. That faint line at the top is the trail left by the meteor, while the fuzzy red patch above it is the nucleus of M31, the Andromeda Galaxy.

Below is the wide-angle shot of the meteor - the meteor just comes into camera-shot at the top. You can also see the line of bright stars that make up the Andromeda constellation. The meteor is just above Beta Andromedae (traditionally known as Mirach)  

Below is a picture of a second meteor I'd captured later at the western edge of the Andromeda constellation. The bright star at the right of the picture is Gamma Andromedae (Almach). 

In the wide-angle shot below, the meteor just enters camera-shot at the right-hand edge of the photograph.

The final meteor I captured was on the second camera aimed at Cassiopeia.You can see it streaking across the sky near the top left-hand corner of the picture below.  At the bottom of the picture is the distinctive 'W' shape of the Cassiopeia constellation.

There were, of course, also the usual dotted line streaks that were left by aircraft, such as in the picture below.

In the picture below, the red and white navigation lights of another aircraft are even more obvious.

My photo session started at 11.45 pm and ended at 2.30 am. By that time, the Andromeda Galaxy had just moved out of camera-shot and the beautiful Pleiades are just coming into view  at the bottom of the picture below.

And, finally, a short video treat for you. Below is a video file consisting of the 200 time-lapse shots I took looking east, where you can see the Anrdomeda constellation slowly rising during my two and a half hour session that night, with the Pleiades making abrief appearance right at the end

All photographs and video on this page  © Sabri Zain 2013.

Monday, 15 October 2012

Andromeda's little sisters

We had few days of relatively clear skies over Longstanton last week, so I pointed the telescope in the direction of the Andromeda Galaxy, or M31. But my target for the night was not the Andromeda Galaxy itself (of which I've already written something here and here) but the oft-overlooked 'satellite' galaxies close to it.

A satellite galaxy is a small galaxy that is in orbit around a much larger, more massive one. A satellite galaxy orbits a larger galaxy due to gravitational attraction. In a pair of orbiting galaxies, if one is considerably larger than the other, then the larger is the "primary" and the smaller is the satellite. 

Our own Milky Way Galaxy, for example, has several satellite galaxies, including the Large and Small Magellanic Clouds (which, unfortunately, are not observable from the northern skies of Longstanton). The Andromeda Galaxy has at least 14 dwarf galaxies. The brightest and closest of these is M32, which is the fuzzy ball right at the bottom the picture above. The second brightest. and a little further away from M31's core, is M110, which is the fuzzy patch to the upper right of the Andromeda Galaxy in the picture above. M31's other satellite galaxies are, unfortunately, much fainter and unobservable with my my tiny amateur scope.

M32 is a dwarf elliptical galaxy can be seen even in small telescopes as a slightly elongated bright patch due south of M31's central region. It is, in fact, so bright that, looking at the picture above, you might even think that it is a star. However, if you zoom in on M32 in that picture and compare M32 with the two actual stars above it, you might notice that M31 looks more nebulous and less intense than the stars (see picture below). The difference is even more evident if you look at the negative image on the right

Although its diameter is only about 8,000 light-years across and its total mass about 3 billion solar masses, M32 has a nucleus comparable to that of its big sister M31, with some 100 million solar masses in rapid motion around a central supermassive object. M32 also has a stellar population similar to that of larger ellipticals, including a mixture of mostly old, low-mass stars and some intermediate-age stars richer in heavy elements, though it lacks globular clusters. These facts suggest that M32 may once have been much larger but then lost its outer stars and globular clusters during one or more close encounters with M31. These stars and clusters would have become part of M31's halo.

M32 contrasts markedly with the other bright satellite of the Andromeda Galaxy – M110. Messier 110 is a dwarf elliptical galaxy and there is certainly no mistaking M110 for a fuzzy star - it isa the fuzzy patch above right of M31 in the top-most picture and has a halo around its nucleus, just like its big sister. M110 is 16,000 light-years across and has an estimated mass of 10 billion solar masses. It also contains some dust clouds and hints of recent star formation, which is unusual for dwarf elliptical galaxies in general.

All photographs on this page  © Sabri Zain 2012.

Sunday, 30 September 2012

Photographing Orion

Those of you who read my blog article on the Orion nebula last week may be wondering why there is such a difference in quality between the two images I took below. They were both taken using the very same telescope, at the same magnification, using exactly the same camera and camera settings, and under the same observing weather and lighting conditions. The first image below is so much clearer than the second due to three main reasons - the eyepiece, a filter and tracking.

Both photographs were taken using a technique that is known as afocal photography. This involves attaching your camera to a telescope eyepiece, using what's called a camera T-adapter and a T-ring. You need a T-adapter for your make of camera (in my case, this is an Olympus Camedia C-4040Z digital camera), which you screw into the lens thread of your camera. You then attach a T-Ring to the adapter and this allows a telescope eyepiece to be attached to it. This assembly is then mounted into the eyepiece holder of your telescope, as in the picture to the left. So instead of your eyes looking through the telescope eyepiece, it's the camera that is looking through it. You would then focus your camera to infinity, focus the telescope until you get a sharp image and then you're ready to start shooting.

The first big difference between the two images I took of Orion is down to the 25mm telescope eyepiece I used. The poorer image was taken with the Meade Series 4000 25mm Super Plössl eyepiece that is provided as standard with my Meade ETX-80 telescope. Now, there's absolutely nothing wrong with the Series 4000. But using a higher quality eyepiece will really make a world of a difference with your views - even with a small aperture scope like the my ETX-80, So for the first image above, I used Meade's Series 5000 25mm eyepiece. This is a high-quality eyepiece with a wide 60° apparent field-of-view, premium grade optical glass with multi-layered coatings for maximum light transmission and all its internal metal surfaces blackened to maximize image contrast. The difference in quality is reflected in its price as well - a standard Meade 25mm eyepiece costs about £20, the Series 5000 is closer to £90.

The other element I added to the mix was a nebula filter. Nebula filters are attached at the end of your eyepeice and they significantly reduce light pollution by blocking out light that is emitted at the wavelengths of articifical lighting from housing, buildings and street lights. Light from emission nebulae and planetary nebulae have a different wavelength of light than streetlights and the light of a nebula passes right through the filter. So the nebula filter blocks out the sky glow to add contrast, making emission and planetary nebula more visible.

A word of warning though - nebula filters are great for nebulas, but not stars, star clusters, planets or galaxies. These objects emit light from all wavelengths including the same wavelengths as street lights which the filter blocks - so a nebula filter would diminish the view of such objects and actually make things worse!

And, finally, the last step in producing a good sharp image is tracking. 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 - the star will appear to travel slowly across your field of view in the eyepiece.The poorer image above was produced using very little tracking, so as the stars moved, the trail of light left by its movement is captured on the image. However, in the second image, I used my telescope's computerised tracking function, which makes small adjustments to the telescope's altitude and azimuth settings so that it moves in harmony with the sideral motion of the stars. You can read all about sideral motion at another blog article I wrote.

All photographs on this page  © Sabri Zain 2012.

Sunday, 23 September 2012

A trickling stream of stars

In my blog, we've already taken a look at two famous star clusters, the Pleiades and Hyades. Today, we'll be looking at a star cluster that is mostly ignored by backyard astronomers, partly because  it is not listed among the famous Messier objects, nor is it found in even the much more comprehensive NGC catalogue. It doesn’t appear on many sky atlases and it is rarely mentioned in articles. many beginning stargazers learning their way around the deep sky may not be aware of this spectacular gem. That object is known as The Alpha Persei Cluster, also cataloged as Collinder 39 and Melotte 20.

The Alpha Persei Cluster is a very easy star cluster to locate. This time of the year, it should be around the northeastern horizon, and quite high above the horizon when it's dark. Everyone knows the 'W' shape of Cassiopeia and the Pleiades' sprinkling of jewels. Now just look for the very bright Capella and its three 'kids' and, as you can see from my picture below, the Alpha Persei Cluster should be smack in the middle of the triangle formed by those three objects.

As you can see from my picture below, the cluster appears as a lovely stream of stars trickling down the night sky, with its brightest member alpha Persei (Mirfak.), at its central star. Many astronomers refer to this cluster as an association because it is loosely bound by gravity. This loose type of open cluster is also called an OB-Association since the clustered stars are mainly of the young, massive, and hot spectral types O and B. These associations are quite unstable and have short lifetimes before they evaporate into space. The cluster is not rapidly dispersing but its members are moving in the same direction.

A closer look at the star will reveal the brightest members of this cluster, including Alpha, Delta, Sigma, Iota and Psi (see below). A rich-field telescope, such as my Meade ETX-80, gives the best views of the Alpha Persei cluster - keep the magnification under 20x. Even at such low power, under dark cloudless and moonless skies, you’ll see about 30 bright stars - perhaps somewhat less under light polluted skies such as at Longstanton. All told, there are more than 100 young stars brighter than magnitude 12 spread across its 3° width.

If you look up further north, lying between Mirfak and Cassiopeia, you'll find not one but two quite beautiful clusters, quite close to each other. In fact, this object is known as the Double Cluster and consists of the pairing of two magnificent clusters, NGC 869 and NGC 884. You can just about see those two clusters in my photograph below - they are those clump of stars at the top and bottom right of the picture.

If you take multiple exposures of the clusters and stack them together, the two clusters are more evident, as in the picture below.

Finally, perhaps the most famous star in Perseus is Algol (in the centre of my picture below). This is a variable star - regular as clockwork, every 2.867 days, the brightness of the star plummets from a relatively bright magnitude of 2.1 to a dim 3.4 (30 percent of normal). The whole event takes only a few hours. The next night time the Algol minima takes place is at 1:21 am on October 10th, so I'll see if I can take a few pictures of that and tell you all about it - weather permitting, of course!

All photographs on this page  © Sabri Zain 2012.

Saturday, 22 September 2012

The Orion Nebula

You know that the summer is gone and winter is not too far off when the Orion constellation once more adorns our night sky in all its glory. If you want a friend, acquaintance or even your six-year old son to become enraptured with backyard astronomy, there are four things you should show him through your telescope - the Moon, Jupiter, Saturn and, the crowning jewel of them all - the Orion Nebula.

Even the non-astronomer will probably be able to spot the famous line of three stars pictured below, known as Orion's Belt. Just below that 'belt' is another line of stars - Orion's Sword, and the Orion Nebula is right in the middle of that 'sword'.

'Just' 1,300 light years away from us, the Orion Nebula is the closest nebula to us, and the brightest, so it can be seen with the naked eye. What you'll probably see is pictured below - a tenuous, but clearly visible, hazy patch of light. a few rather bright stars. These stars are what illuminates the clouds of dust and gases of the nebula, which otherwise would not be visible at all. The brightest of these stars are Theta–1 and Theta–2.

With a telescope, though, and in good observing conditions, you will be able to see the full extent of the nebula and perhaps even glimpse it's greenish blue hue, perhaps even a reddish tint. 

However, you will need either time-lapse or long exposure photography to view the nebula in all its colour and glory. The picture at the top of this article was produced using afocal photography, viz. a camera attached by adapters and T-Rings to a 26mm eyepiece on the telescope and operated remotely by computer. I took 24 exposures, with each exposure lasting 3 seconds (to minimize the star-trailing), and the 24 images were then 'stacked' together  

in black and white, as in the picture below, you can see that the contrast improves and one can actually make out the areas of swirling black clouds of nebular gas.

The nebula is a vast, cold cloud of gases and dust that does not emit light and is composed mainly of hydrogen (91%), helium (9%), carbon (0.05%), oxygen (0.02%), and nitrogen (0.02%), as well as smaller quantities of sulphur, neon, chlorine, argon, and fluorine. The gases and dust reflect the light of the nearby stars, but in the vicinity of the hot young stars the gases in the nebula are excited by the ultraviolet light emitted by these stars and so emit their own light. Although the nebula may appear tenuous and transparent, this 'clouds' actually contains the matter of 10,000 Sun-like stars! It is from such 'clouds' that stars like our sun and even planets like ours are 'born' and the Orion Nebula has revealed much to astronomers about the process of how starsand planetary systems are formed from collapsing clouds of gas and dust.

All photographs on this page  © Sabri Zain 2012.

Mystery object passing Jupiter

While taking a series of four 3-second time lapse photographs of Jupiter and its moons on Thursday night, I captured an object moving which I cannot fully explain. You can see the object moving below Jupiter in the video above, moving in the opposite direction of Jupiter rising in the night sky. This series of pictures was taken over a period of about two minutes, so it's too slow or distant to be an earth-bound aircraft. It is headed in the opposite direction as the motion of the night sky, so it's not a star or solar system object. And it's not a reflection of light on the lens, hot pixel or other photographic artefact, as these would be stationary and not appear to move. So what in the Universe could it be? The mind boggles.

Below are the four photographs taken, so you can have a closer look and perhaps help me work out what exactly that object is. These were taken afocally,  viz. a camera attached by an adapter and T-Ring to a 26mm eyepiece on the telescope and operated remotely by computer. Each exposure was for 3 seconds. Unfortunately, I could not take any further photos of the object, as it had gone past the eyepiece's field of view after the fourth shot.

All photographs on this page  © Sabri Zain 2012.

Sunday, 9 September 2012

In search of the Galactic Plane

Almost everyone knows that the galaxy our Solar System is located in is called the Milky Way but a lot of people don't realize that you can actually see the Milky Way from the comfort of our Earth-bound back gardens. Well, obviously not the whole of the Milky Way galaxy - you'd have to be well outside of the galaxy, in a starship or some alien observatory in the Andromeda Galaxy, to do that. What we can actually see is the Galactic Plane of the Milky Way - the plane in which the majority of our galaxy's mass lies. 

Every star you see in the night sky is part of the Milky Way but you can also see a hazy band of 'milky' white light (hence the name of our galaxy) some 30 degrees wide arcing across the sky.   The Galaxy appears like a band (as seen in the photograph below from the European Organisation for Astronomical Research in the Southern Hemisphere in Chile) because that's what you see when a disk-shaped structure is viewed from inside. And you don't even need a telescope to see it - your trusty Mark 1 eyeballs are the best optical equipment to use.

However, if, like me, you are living in or near a city such as Cambridge or even a suburb such as Longstanton, the chances are it will be almost impossible to see. The light pollution from from street lights, buildings, houses and vehicles will completely wash out any of the Milky Way's white 'haze' (not to mention a good number of normally visible stars). Bright moonlight would make it even more difficult to see and if it's cloudy, well, you might as well go inside and watch the 'The Sky At Night' on the BBC instead.

To illustrate, the picture below was taken outide my house last night, with a bright half moon, some hazy cloud and the scorching lights of the A14 and a guided bus station blazing away just a few miles away - not to mention a b*$$&y street light just in front of my house. Looking westward at this time of the year, I should be able to see the Galactic Plane cut across the constellation Cygnus and Cepheus. However, as you can see the photograph below, all you'd probably be able to see in these very usual conditions would be the bright line of stars at the bottom that form the cross Cygnus and a handful of Cepheus' stars at the top.

In better seeing conditions, with no moonlight or cloud, such as in the picture below, you'd probably be able to resolve many more stars - but the light pollution would ensure that you'd still be hard-pressed to see any hint of the Galactic Plane.

However, the Galactic Plane IS there! I'd taken 36 exposures of that same scene in my first photograph above and 'stacked' them using astronomical imaging processing software so that I'd be able to squeeze every tiny photon of light captured in each exposure (the technique is explained in my earlier blog 'Let there be Light!'). The resulting image is shown below:

You can probably now just about make out a band of hazy stars concentrated in the middle of the picture. You might also see some dark 'clouds' within that band. Dark regions within the band correspond to areas where light from distant stars is blocked by interstellar dust.