Observing from Jan 2014
December 2014 – Jupiter rises high and look out for the Geminid meteors on December 12th and 13th
On Friday 12th and Saturday 13th December you may get a chance to see the Geminid meteor shower. Admittedly the weather forecast is looking a bit shaky but it could prove to be an excellent display. The moon rise shortly after 11pm in Leo and is about ½ so will provide some obstruction later on, it is almost 40 degrees away from the radiant point (near Castor). The Geminids are very variable but can be very good. They appear to be different to most other meteors. Meteors generally come from the tails of comets that have crossed the earth’s orbit in historical times. The small particles suspended in space enter the earth’s atmosphere at high speed and burn up leaving their brilliant trace. Meteorites, which by strict definition are objects that make it to the ground, are quite different in origin. They are remains of pieces of solid rocks or possibly asteroids left over when the solar system formed. The Geminid meteors are very unusual in that they are suspected of coming not from a comet but an asteroid type object called 3200 Phaëton. This object has an unusual orbit that brings it closer to the Sun than any other named asteroid. For this reason, it was named after the Greek mythological character of Phaëton, son of the sun god Helios. It is 5.10 km in mean diameter.
But the mystery does not end there. The orbit of 3200 Phaëton is more like that of a comet than an asteroid and it gives off a dust trail; it has been referred to as a “rock comet” although is suspected to be a type of carbonaceous “B type” asteroid related to Pallas. These asteroids contain unusually high amounts of volatiles that are believed to be remnants from the early solar system.
As with all meteor showers it has a radiant, in this case in Gemini, close to the lovely double star Castor (α Geminorum). The meteors may appear anywhere in the sky but will appear to radiate from this point. They should be visible late in the evening or early hours on the 12th and 13th.
Jupiter is now rising in Leo at a reasonable time, at the end of the month it rises at around 8pm and culminates at 03:12hrs GMT with a diameter of over 43 arc seconds. At culmination it is very high at just over 53 degree from the horizon in this part of the world. It is very easy of course to find as there is nothing else anywhere near a bright in the same part of the sky. It forms a small triangle with Regulus (α Leonis) and Algieba (γ Leonis). This latter star is distinctly yellow (K type) to the naked eye and at magnitude 2.2 is easy to spot. Algieba means the forehead although is better described as the mane or even the neck of the lion. With a small telescope it is a very beautiful double with a G type (same as the Sun) companion. Both of the components are giants. They are 4” apart and reasonably easy to separate although not a binocular object.
Regulus is also a multi-component system with at least 4 components – A plus companion, B and C. Regulus A itself is a spectroscopic binary, its companion can only be detected with a sensitive spectrometer. The B and C components are 177” from A so can be observed in a telescope.
While we are in this part of the sky it is worth considering the constellation of Cancer. This is a constellation that unless you have deliberately gone looking for it you may never have noticed it as it is so dim! Its brightest star (beta Cancri) only has a magnitude of 3.5. Presumably its main claim to fame is that it is on the ecliptic and so a sign of the zodiac. As such planets such as Mars can often be seen traversing it. It also boasts a rather spectacular open cluster called Praesepe (M44 or NGC2632). This is visible on a good night as a fuzzy patch but is spectacular through binoculars or a telescope on low magnification.
September/October – Some very mature red giants to look for and plenty of open clusters.September this year has been the driest on record and there have been a number of good observing evenings although typically for the time of year it has often been somewhat misty. The spectacular summer constellations such as Cygnus, Aquila and Hercules are now well to the West in the evenings and the Square of Pegasus now dominates the southern sky.
Pegasus is an ancient constellation and named after the winged horse of Greek mythology. For some reason the horse is usually depicted as upside down – the star Enif is the creature’s muzzle. The constellation is dominated by the square asterism. It is sometimes said that if you count the number of stars that are visible to the naked eye within the square of Pegasus it will give you an estimate of the minimum magnitude that you can expect to see. The square is comprised of Alpheratz – a type B (blue) and variable star of magnitude around 2.05; Scheat an M type (a red giant) pulsating variable; Algenib, another type B and also a pulsating variable of magnitude around 2.8 and Markab also a type B of magnitude 2.45. It is believed that both Markab and Algenib have exhausted their supply of hydrogen and are now in an expansion phase towards becoming red giants like Scheat. Algenib is classified as a Beta Cephei variable (this is not the same as a Cepheid variable) and it pulsates with a period of 3 hours 38 minutes. This is due to regular changes in the star’s atmosphere expanding and contracting. Enif is an irregular variable and a type K orange super giant. Such star types are often irregular variables as they are very mature, large and unstable.
M15 is a nice globular cluster of magnitude 6.4. It is estimated to be around 12 billion years old – which makes it one of the most ancient globulars known. It is also one of the most densely packed as it has undergone a core collapse. Individual stars are resolvable with an instrument of 6” (150 mm) or more of aperture.
Adjoining Pegasus and to the east is Andromeda, named after the mythological daughter of Cepheus and Cassiopeia. Andromeda was offered as sacrifice to the sea monster Cetus although was rescued by Perseus. The constellations of Cepheus and Cassiopeia are to the north of Andromeda, Perseus is to the east (remember that east appears to the left on a map of the sky!) and Cetus is to the south east.
Between Cepheus and Cassiopeia you should be able to find M52. An easy open cluster. Between Cepheus and Cygnus is another large open cluster M39. In fact there are many open clusters in this part of the milky way especially through Cassiopeia. Do not forget the double cluster between Perseus and Cassiopeia, a perennial favourite.
Also near Cepheus and quite easy to spot is Herschel’s garnet star – easy to spot because of its red/orange colour (Mu Cephei). This is another pulsing variable with a magnitude of around 4.2 – so it is easy to spot. It is in fact a huge star about 1000 x larger than our own Sun and around 350,000x brighter. It is another star that is nearing the end of its days and it is in a phase of fusing helium into carbon. It would be expected to become a supernova at some point in the coming millions of years. It is very easy to see with binoculars.
For those that enjoy planetary observation Uranus is well placed with an altitude of over 43 degrees at culmination (when at its highest and due south). It is only a modest 3.7 arc seconds in diameter and you will not see any surface features but it is a clear blue disc in a telescope. The picture below was taken from Abergavenny in less than ideal conditions.
Moving away from the Milky Way this is a very good time for observing our two brightest galaxies, the Andromeda galaxy and the Triangulum galaxy. Both are easy binocular targets. In fact the Triangulum galaxy is easier to see with binoculars than with a telescope as it is quite diffuse. Look for it on a dark moon free night.
July/August – The sky does not get dark until very late but there are some brightly coloured gems to looks for.
This blog is a double month as July does not really get dark in this part of the world and observing is limited to a few bright objects. As it happened July turned out to be a beautiful month weather wise – there is no pleasing some people! Still solar observing has been very good and the Sun is still really very active with sunspots and particularly filaments being present most of the time. Usual warning do not even attempt to observe the sun unless you are sure you fully understand the dangers (see below). The size of some of these phenomena can be truly staggering. The picture below was taken from Abergavenny on the 3rd of August. The long diagonal filament just below centre left is just less than 310,000 kilometers in length and around 4500 kilometers wide. The long sinuous filament just right of centre in the top half of the image is some 225,600 kilometers long. The swirling features in the granulation of the Sun’s surface clearly show the stresses in the plasma that lead to the formation of the spots. The pale plage are also clearly visible. This picture was taken with an H alpha telescope but in fact plage and faculae (light patches) are often visible near the edge of the Sun with just white light filters.
Even if it does not get completely dark there are things that can be observed very readily, particularly multiple stars. It has been estimated that the majority of stars are in multiple systems although this is disputed by some as many dim red dwarfs are hard to see and therefore include in the assessment. However it is clear that a large proportion of the bright stars we see have companions. There are a number of types of multiples. There are optical binaries for example – the separate stars can be observed with a telescope. Then there are spectroscopic binaries – only by measuring changes in the spectrum of a star does it become evident that there are two star orbiting each other very closely. Of the optical doubles there are real binaries – the two stars are gravitationally linked and also optical doubles – in this case they just appear to be close because they are in the same line of sight. Over many years it is often possible to observe and plot the stars of real doubles orbiting each other.
Very few multiples can be observed as such with the naked eye but binoculars can certainly show quite a few. One famous exception is Mizar and Alcor in the tail of the Great Bear (Ursa Major). This can be seen as a pair with keen eyes. A telescope shows Mizar itself to be a pair. Spectroscopy shows each component of Mizar are each binaries as well! Clearly a complex multiple system.
There are a number of good reasons to go hunting for these objects. They are a very convenient test of the quality of a telescope. The Dawes limit is an expression to work out the maximum resolution of a telescope based on its aperture. It was determined empirically by W. R Dawes based on observations of binary stars. Double stars also show off the colours of stars nicely as two close objects can be easily compared. Apart from that they can be very beautiful. There are a number of classic doubles that are well worth hunting for in the sky at present. See how many of these you can find and separate. You will need an aperture of at least 75 mm for the more tricky ones and 150 mm should be capable of separating all of the examples mentioned here.
We can start with one of the easiest and also the most beautiful – this is Albireo or the head of the swan – Cygnus. Its latin name is Beta Cygni. Visually it is stunning with an orange magnitude 3.1 star close to a blue/green magnitude 5.1 star. At just over half an arc minute they are very easy to separate in a small telescope. In fact the orange component (A) turns out to be a very close binary as well but you will not be able to separate them with amateur equipment.
Another easy one is the nose (or snout) of the Dolphin – Gamma Delphini. This consists of two yellow stars, one pale yellow (mag. 4.3) and the other creamy (mag. 5.1). I should point out that the colours you may observe are very subjective. It can be easier to see the colours more clearly if the image is slightly de-focused. These two stars are about 9 arc seconds apart so easy to split.
The next double is easy at first but has a surprise in store. This is called Epsilon Lyrae and is very easy to find as it is very close to the beautiful Vega. Even through binoculars the main components of this double are easy to split at over 200 arc second separation. In theory they can be seen by eye but I have never managed to split them in this way. After you have found them increase the magnification and you may see that each of the components are themselves doubles. This is also called “the double double” for obvious reasons. You may not see the smaller doubles at first and it does take reasonably good seeing conditions. The finer doubles are only separated by about 2 arc seconds. If you do not see them one night keep trying – when the seeing clears you will see them.
Across to the East and the most easterly star in Pegasus, Almaak, is a real beauty. I think it is a strong rival for Albireo with orange and blue companions.
Now you are getting confident it’s time to go for a trickier example – μ Cygni. It is in the south east of Cygnus. It consists of 4 stars; 3 are very easy to see and so far apart that at first they do not really look associated. But concentrate on the brightest and increase the magnification as far as you can. You will probably need at least a 150 mm scope to see this – it is reasonably easy on a good night with a 200 mm aperture. You may just notice that this brighter component is in fact two stars really close together. In fact they are separated by 1.6 arc seconds. With this pair many observers may be at their limit – do have a go.
The table below gives information on some of the best multiple stars to be seen this month and next. The letters in the left most column refers to the chart below. Some are very easy to find e.g. Almaak, εLyra, Albireo, γDelphini and μ Cygni; 61 Cygni is more difficult. If you possess a go-to simply enter the coordinates.
I suspect that there are many amateur observers that own go-to equipment but have not managed to get the hang of using coordinates. Why not try using the coordinates given here to practice on these easy to find objects. It is a really worthwhile exercise as the built in catalogues do not always have the objects you want to look at or may not have an easy reference number – particularly for stars. Your instruction manual will tell you how to do it and if you get stuck ask one of the regular observers in the society’s meetings they will be able to help.
There are thousand more visual binaries to explore – I hope this has whetted your appetite for those misty – not-quite-dark summer nights.
June 2014 – No dark nights – try having a look at our nearest star – The Sun
At this time of the year observing at night can be very difficult as the nights are very short and for a month or so it does not get really dark at all – looking for those elusive “fuzzy patches” is a real challenge. Many observers simply give up in the summer and put their equipment away until the dark nights are with us again in August. There are still some planets around, for example Mars and Saturn, and these can be observed successfully even in twilight. But they are getting low very by the time night falls and a very small. However there is one object that is in a perfect position to observe, our nearest star – the Sun. There is always a need to caution that observing the Sun must be done with care. Never look directly at the Sun directly and if you are using a telescope or binoculars they must be correctly filtered – more on that later.
The Sun is at its most interesting when it is most active, this occurs approximately even 11 years. It was widely predicted that the maximum would be at a maximum in 2013 but it has been delayed. It turns out that we are at present in the maximum. In our present case we are in the second peak of the maximum, which unusually is exceeding the level of the first peak (that occurred a couple of years ago).
There are a number of safe ways of observing the Sun. The simplest is pinhole projection; all you need are two pieces of paper. Make a pinhole in the centre of one piece and hold it so that it casts a shadow on the second piece. On the second piece of paper you should be able to observe a small light disk in the centre of the shadow – this is an image of the Sun! With this method you will be able to observe and track large sunspots as they move across the face of the Sun. It must be said though that this method is pretty limited in what it can show.
An improvement on simple projection is to use a refracting telescope. The telescope must be mounted on some sort of mount – a photographic tripod will suffice. Fit a cheap eyepiece (as there is a chance it will overheat and be damaged). DO NOT LOOK THROUGH THE EYEPIECE OR FINDER SCOPE UNDER ANY CIRCUMSTANCES. I usually recommend that the finder is removed to avoid accidents or at least taped over.
Hold a piece of white card about 30 cm behind the scope and you will see the shadow of the telescope tube. Move the tube on the mount until all you can see is a circular shadow of the tube – this means it is pointing at the Sun. You should now see an image of the Sun projected onto the paper. This can be a bit fiddly and definitely gets much easier with a bit of practice. You will now need to adjust the focus to get a clear image. In this way you will be able to see even quite small sunspots.
If you want to use a telescope or binoculars for directly viewing the Sun it is possible to purchase special metallised film that can be made into a custom filter for your instrument (for example Baader Planetarium solar film).
Sorry to keep going on but another word of caution. Some (cheap) telescopes are provided with a “Sun filter”. This is intended to be used screwed into the eyepiece. Throw it in the bin and do not use it. They are very dangerous as they are prone to overheating and cracking.
The special metallised film can be used with just about any instrument. The pack contains full instruction on its use. Do not be tempted to use other metallised films that have not been specially designed for the purpose, they are simply not adequate. In this way it is possible to make superb solar filters for less than £20. The picture below shows a 200 mm aperture Newtonian reflector fitted with such a home made filter. Notice that it is not necessary to have the filter cover the full aperture.
In this case the filter has been made offset to avoid the central obstruction of the secondary mirror. Often telescopes have a suitable hole in the end cap that can have a piece of this film stuck over it and that works very well. There is actually an advantage in using a hole that is smaller than the full aperture of the telescope. The hole acts to “stop down” the telescope which increases the contrast.
The pictures shown below in the March 2014 blog were taken using this film (on a 102 mm refractor). With this method you can get some great views of sunspots, granulation and near the edge (limb) the pale patches called plage. If you do not feel you want to make your own filter it is possible to buy ready made ones although they are more expensive. If you do use this kind of filter always check it has no holes before use – although I have found the film to be very robust. As the aperture can be reasonably large the resolution can be good. It is best to observe early in the day before the atmosphere gets too heated and disturbed.
Probably the best way to observe the Sun is using telescope that has been specially manufactured for the purpose. These telescopes use very precise narrow band filters that show the spectral lines emitted by hydrogen (hydrogen alpha line 656.28 nm) or other elements. There are a number of manufacturers of these, the Coronado Personal Solar Telescope (PST) is very well known and other manufacturers such as Lund (shown below – the Lunt 35THa) also offer excellent instruments. The downside is that they are pricey – starting at around £650 for the most basic models (35mm aperture) and costing many thousands of pounds for the most advanced. They work by filtering everything except for an extremely narrow band of light – usually less than 0.75 Angstroms wide –around 7 times the width of a hydrogen atom! The narrower the band pass the more the contrast.
These telescopes render the solar atmosphere essentially invisible and give wonderful views of the chromosphere. They will show dramatic views of sunspots, granulation, filaments, plage, flares and last but not least prominences and spicules.
The picture below was taken by such an instrument from Abergavenny on the summer solstice this year. The first thing that you will notice is the obvious granulation from convection cells at the surface.
On this day there were very few sunspots but filaments, plage and prominences were easy to see. These features change with surprising rapidity and it is common to view flares of plasma being emitted at speeds of up to750 thousand miles per hour! It is quite easy to estimate the size and speed of these prominences when you remember the diameter of the Sun is 1.4 million kilometers, by estimating the proportion of the diameter.
The sequence of 5 pictures below shows the evolution of the “Y” shape prominence at the 8 o’clock position over a 1 ¾ hour period. Considering this prominence is five times larger than the Earth (63,000 km) the changes are huge. Often prominences can show much more dramatic changes than this. There are very few astronomical sights that change as rapidly and dramatically while one observes them.
So solar observing can be a fascinating alternative on sunny days. It can be done quite inexpensively although the better equipment can be pricey. If you do get the chance to view the Sun through a hydrogen alpha telescope you will not be disappointed. Be safe and ensure you fully understand the requirements for safely observing. If you have concerns do not hesitate to contact one of the observers in the society. Remember after this year it will not be as dramatic for another 11 years!
May 2014 – Don’t forget our nearest neighbours
At this time of year the nights are getting shorter and shorter, the longest day is the 21st June, and it gets harder to observe the dim deep sky objects. However there are still solar system objects around that are much less sensitive to the twilight.
Mercury is visible if you have a good western horizon. At the end of May the Sun in Abergavenny sets around 20:45 BST and Mercury is just north of west at around 18 degrees above the horizon and a magnitude of about 1. It is a small object at under 10 arc seconds and it is very difficult indeed to observe any surface feature but it is possible to see the crescent shape. It is just past its maximum elongation (of just over 22 degrees); this is the apparent angle subtended between the planet and the Sun as seen from Earth. This means that it is at its most easily visible. It can be seen with the naked eye and of course binoculars or a telescope. The usual caution applies, under no circumstances try searching for the planet when the Sun is above the horizon. Accidentally catching a glimpse of the Sun will destroy your eyesight. Simply just wait until the set has set – it is easier to find then anyway.
Jupiter can still be seen in the west as it gets dark but sets just before midnight, so the apparition of this planet is drawing to a close. Still worth a quick look though although its size at around 33 arc seconds is just over 2/3rds of what it was a few months ago.
Mars is still a splendid object and very easy to find, it is just about on the meridian looking south at sunset and 35 degrees above the horizon. It is getting smaller all the time and is just under 13 arc seconds at the end of May/early June. It is just at the bottom of the bowl of Virgo. The blue star to the east and a bit lower is Spica;. if you look to the east of Spica and reasonably low on the horizon you will come to the main event – Saturn.
Saturn is always a spectacular sight and as mentioned before its rings are nicely inclined this year so it makes a particularly dramatic sight. By the end of May it culminates (is exactly due south) at 15 minutes past midnight (BST). It is of course at its best in a telescope; even modest ‘scopes will show the rings but in telescopes larger than about 8” aperture the planet makes a breath taking sight. If you have a telescope or get a chance to look at it through one, look for the dark Cassini division in the rings. It is easily visible in a 3” aperture or possibly even smaller, particularly when seeing is steady. This ring is 4800 km wide and divides what are known as the A and B rings. It was named after its discoverer Giovanni Cassini who first observed it in 1675 from Paris with a 2.5” refracting telescope. The B ring is closest to the planet.
If you are lucky enough to have an instrument larger than 8” in aperture you might even catch a glimpse of the Encke division. This is an even thinner dark line further out and only and only 325 km wide, I have glimpsed and imaged it a couple of times in the past few weeks. Also quite evident is the crepe ring, this is a semi transparent ring close to the planet and also called the C ring. It was first observed in 1850 by a number of independent observers. Admittedly it is easier to image than to observe with the eye and requires an advantageous position of the rings, as we have this year, very steady seeing and a quality instrument.
The gaps in the rings are caused by a number of moons that orbit the planet. These moons have resonant orbits that cause any material that would be in the gaps to be moved out by their gravitational field. For example in the case of the Encke gap a tiny moon called Pan keeps it clear, the Cassini division is maintained at least in part by the moon Mimas.
I took the picture below on the 30th April this year with a webcam type camera on an 8” Maksutov reflecting telescope and a number of the features described are clearly visible, including a faint suggestion of the Encke gap. The crepe ring is just visible, particularly where it passes in front of the planet’s disc. In this picture it is also possible to see the darker southern pole (N is at the bottom). If you have the opportunity I cannot recommend highly enough that you have a look as this beautiful object.
On the subject of solar system objects why not have a go a looking for some dwarf and minor planets?
Vesta is one of the largest asteroids in the solar system and is technically classified as a minor planet. It has an average diameter of around 525 kilometers. At present it is reasonable easy to find and in binoculars appears as an easily visible star. In larger telescopes it is also star-like but does not show the typical point like aspect that stars do. With a diameter of 0.6 arc seconds it is at the very edge of resolution of the vast majority of amateur instruments so cannot be resolved into a disk. The simplest way to find it and recognise it is to use some planetarium software such as Stellarium, Starry Night or Carte du Ciel to find its location (if you have a go-to scope it is then dead easy, simply punch in the coordinates that the planetarium software will give you and off you go). Without go-to it is a case of looking for the stars indicated in the planetarium software and star-hopping until you find it. Vesta presently has a magnitude of around 5.7 so although very difficult to see with the naked eye is an easy object in binoculars and obvious in a telescope.
There is another way to find asteroids, observe and either sketch or photograph the star field where you think it should be, then return the following night and repeat. Any asteroid will have seen to have moved. I did this for Vesta on the evenings of the 14th and 15th of May. The result is shown below, Vesta has clearly moved. You need to leave at least a few hours between the pictures, the movement after 1 hour for example is only just detectable. Vesta is close to the meridian at around 10:30 BST at the end of May at an altitude of around 41 degrees above the horizon. These pictures were taken using a 5” reflecting telescope with a DSLRon an unguided equatorial mount (10x 1 min exposures each). Vesta can be seen just left of center on the left picture and moves to the right on the second.
Ceres is not far from Vesta and although almost twice the size (mean diameter of 950 km) of Vesta is significantly dimmer with a magnitude of about 7 at present. It is the only dwarf planet in the solar system. It can be found at present just to the east of Vesta and at a similar altitude in Virgo. The figure below should help you locate these objects in relation to Mars and Saturn.
So get out and make the most of the remaining darkness to see some of our closest neighbours in the solar system, if you do nothing else then marvel at the beauty of Saturn. Although relatively low it will not be as well placed for many years to come, so let us make the most of the opportunity.
April – magnificent Mars and gorgeous galaxies
April has turned out to be quite a good month so far for planetary observing, Jupiter is still high enough to be worth observing in the early evening and of course Mars is magnificent in the south all evening. As mentioned last month it reached opposition on the 8th of April. This means that the Sun, Earth and Mars are aligned in a straight line. With simple geometry this would make Mars as close to Earth as it can get – however the orbit of Mars is not truly circular but is somewhat elliptical. This means its closest approach is actually a few days after the 8th and is in fact slight larger from the 11th to the 16th April. In fact even in opposition Mars is not at its very best this year. The eccentric orbit can take it to its furthest point from the Sun (aphelion) or its closest (perihelion) with a difference of about 13 million miles and it all depends if the Earth happens to be passing into opposition when Mars is at perihelion. In fact depending on how things line up the Earth can be as close as 35 million miles or as far as 63 million miles away at opposition. This makes a big difference to how easy it is to observe. This month it was around 54 million miles – giving an apparent diameter of just over 15 arc seconds – quite an observing challenge to see details. In 2003 it was at its nearest for almost 60,000 years with an apparent diameter of just over 26 arc seconds; the next time it will get even closer to that will be in late July 2018 at 24.3 arc seconds (35.8 million miles). As luck would have it it will only be about 15 degrees above the horizon then. Time to book a holiday somewhere further South perhaps. Failing that your next chance is in September 2035, from Abergavenny it will be 33 degrees above the horizon and a respectable 24.6 arc seconds. Oh well there are always plenty of other things to look at while we are waiting!
The series of pictures below were taken on various nights after the opposition when there was some good steady seeing. The jet stream has been quite favourable this month. The polar cap in the north is obvious and there are cloud patches on the horizons. You will not be able to see much with binoculars but even modest telescopes will begin to show some details. You will need steady seeing conditions and a 2 inch (50 mm) refractor or a 4.5 inch (114 mm) reflector to start discerning the details. The pictures above were taken with an 8 inch (200 mm) reflector.
Use a high magnification, a rule of thumb is a maximum of 50x magnification for every inch of aperture. So with a 2 inch reflector 100x should be possible. With exquisite seeing and a very fine instrument this can be exceeded. You will find with planets that generally the best magnification is to go as high as you can but without losing the details. With higher magnifications the contrast reduces. In the case of Mars this is not too much of a problem but with a more subtly contrasted subject such a Jupiter – less is often more. I strongly urge you to play around with various eyepieces each night until you find the one best suited to the conditions, the subject and the telescope you are using. Remember to record your best observations and what set-up you were using as this is the best way to learn and improve. To work out your magnification divide the focal length of your telescope (always written on the side as say f600mm) by the focal length of your eyepiece. So for a 600mm focal length with a 6mm eyepiece you will get 100x magnification. The other good tip with planets is that you can save money and have a more convenient experience if you purchase a Barlow lens. This is a “negative” lens that in effect doubles the focal length of the telescope. So in the example above the 600 mm scope will act as a 1200 mm one with a 2x Barlow and with the same 6mm eyepiece would give a magnification of 200x. With a Barlow you double the number of eyepieces you have in effect.
The other benefit with a Barlow is that is easy to use high powers. This is because very short focal length eyepieces normally require you to get your eye extremely close to the lens. This can be uncomfortable or even impossible for spectacle wearers. With a longer focal length eyepiece you do not need to get as close and this is maintained with the Barlow.
This is the time of year for observing galaxies and the best constellations to see them in are Virgo, Coma Berenices and Leo. The reason why there are so many to be seen here is that one is looking out of the plane of the galaxy so there is little obscuring interstellar dust. The trick to observing them is to use a reasonably large scope and have excellent transparency with no Moon and low light pollution. The Abergavenny area certainly has low enough light pollution but it is important to pick a dark starry night with no mist. Galaxies have very low contrast and any mist will simply obscure them. For all but the brightest galaxies you will need at least an aperture of 3 inches. With 8 inches or more galaxies of magnitude 10 are easily within range and a 12 inch will get to magnitude 11.5. Remember that galaxies are extended objects (blobs of light). A star of magnitude 10 is reasonably bright even in binoculars – because it is all concentrated in a point.
The chart below shows the sky in the region of Coma Berenices and Leo. The easiest way to locate this chart in the sky at the moment is to simply look for Mars – shown at the bottom just left of centre. Above Mars you should be able to identify the bowl of Virgo. Scanning the sky vertically above this will lead you to the realm of the galaxies. There are literally dozens. This is one occasion when a “go-to” scope will be found to be a real advantage. One of the most interesting areas is that shown in the red oval and called the Markarian chain. This consists of a line of around 8 reasonably bright galaxies including M86 and M84, most of these galaxies have a common motion.
The ideal telescope for this kind of study is the classical Dobsonian. They are usually of a reasonable aperture – more than 8 inches and can be used to scan the sky quickly. When galaxy hunting do not be tempted to use to high a magnification, this can reduce the contrast. However again it is important to experiment as higher magnification can reduce the background light as well and make the galaxy easier to spot. The other important technique to practice is to use averted gaze. An object may often be spotted more easily by not looking directly at it, look slightly to one side. Finally you will discover that moving the telescope slightly may show up a faint hazy blob that is not visible otherwise. The eye picks up on moving objects more easily than stationary ones. If you cannot spot the galaxies at first keep looking and try the techniques mentioned – once you start to see them it gets easier with more practice – believe me!
Spring has sprung – Plenty of planets and a spotty Sun! March 2014
It may not feel like it but in fact Spring started from an astronomical viewpoint at 16:57 on the 20th March. What that means is that the axis of the Earth is perpendicular to the direction of the Sun, or to put it another way the Sun is directly overhead at the equator. This Vernal Equinox (Ver= spring, Equinox= equal) as it is called has been known since ancient times as it is when the length of day is closest to the length of the night. I say closest because there are a number of effects that ensure it is not usually exactly equal on that date. From his day until the 21st June (the summer solstice) the days will keep getting longer and as we get into July we no longer experience astronomical darkness as the Sun does not set more than 18 degrees below the horizon. This may not seem like a wonderful time for observational astronomers but of course it is the ideal time to view our nearest star – the Sun. It is a good time simply because the Sun is high in the sky and you will be viewing it through much less distorting atmosphere. The summer Sun heats up the ground and the atmosphere quite quickly so it is best to observe it before midday to avoid turbulence.
The two common ways to observe the Sun safely are using white light filters or using ultra narrow band filters. Usual health warning – never ever look at the Sun directly even with the naked eye it is very harmful and with any optical aid you will be blinded instantly.
The images below were produced using a 102 mm refractor fitted with a Baader white light filter. A mosaic of 10 images was produced using a planetary camera designed for the purpose. This camera takes a series of frames at high speed then special software is used to stack these images and average them to reduce noise and hugely improve sharpness. The large image of the Sun was taken from Abergavenny on the 23rd March at around 13:30pm. There is a relatively large number of sunspots visible strewn across the photosphere. We are coming towards the end of the sunspot maximum so it was nice to see this display.
Notice the dark single spot on the right limb. This shows the so called Wilson effect, named after Alexander Wilson, a Scottish astronomer who first observed it in 1769. He noticed the foreshortening effect which demonstrated that the spots were features on the photosphere and not planet-like bodies floating above the surface. He also noticed that when near the edge such spots appear to be depressions. The photograph below shows this area enlarged and the third photograph shows the same spot taken 7 days before on the 16th March; when it was much nearer the centre of the disk and less foreshortened.
It is to my experience relatively rare to see such single isolated spots. It is much more common to see spots in multiple groups, at least usually in pairs as they are arranged around intense magnetic fields with north and south magnetic poles.
Two other things to look out for are the faculae on the limbs, these are pale streaks that show up best near the edge of the sun for optical effect reasons. These are bright areas on the photosphere that are associated with the sunspot activity. Also visible across the entire surface is the fine granulation – a consequence of the constantly churning convection cells.
So much for our own star what about the night sky? Well March has turned out be a singularly poor month for clear transparent skies when we would expect to be hunting down the galaxies in Leo and Virgo. But it has been reasonably good for planets. Jupiter, photographed on the 18th March and shown below, is coming towards the end of this apparition; it is reducing in size and is getting lower in the west every evening. It is still well worth watching though and remember, it is still a great object to look at even in twilight.
We have a newcomer on the scene – Mars is rising and worth looking for in the south after midnight. I took the image below earlier in the month. The dark feature that looks a bit like India upside down is Syrtis Major and the pale patch just to the lower right of it is called Hellas, the white patch is the south polar ice cap. The north polar ice cap is just visible to the top left. Mars will be at its best in early April, it is at opposition on the 8th.
The other planet well to the east of Mars and much lower in the sky is Saturn, but you will need to stay up into the early hours to see it. Saturn is very low this year but its rings are very open so worth studying. The Cassini division is really easy to see at present even in small telescopes, larges scopes may even glimpse the Enke division near the edges of the rings.
The year started wet but February has plenty of planets and a supernova to observe
The year has got off to a wet start with the highest rainfall in January since records began – not the best for astronomy! There have been a few observing opportunities particularly for the spectacular apparition of Jupiter; surprisingly between the showers there has also been some quite good seeing. Good seeing is when the atmosphere is stable – generally when the jet stream is avoiding us and we can use high magnification to see features on planets. For February good seeing will be especially important as there will be a number of the brighter planets on show. Jupiter has already been mentioned and is still a magnificent object through most of the evening. It can be seen in Gemini and is instantly recognizable because it is so bright.
Saturn is beginning to put in an appearance in the small hours. At the start of the month it rises at around 2 am but by the end of the month it rises 1.5 hours earlier. Unfortunately Saturn does not rise very high in the sky and will not do so for some years to come. Saturn takes around 29½ years to orbit the Sun – its position in its orbit dictates where it appears in our sky. The figure below (Feb 11th around 5 am) shows the sky looking south.
The red diagonal line is the ecliptic. This is the imaginary line that describes the path that the Sun follows across the sky. As the Earth and other planets all lie approximately in the same plane the planets never stray very far from this line. In the winter, owing to the inclination of the earth’s axis, the ecliptic is very low in the sky. This is the same reason that the Sun is also low in the winter. For Saturn to rise significantly higher we will have to wait for some years until it moves to a part of the ecliptic that is higher in our sky. Although it does not rise high its rings will be well displayed as they are inclined at around 23 degrees. The size of the disc will be around17 arcseconds, not huge but not too bad.
Unfortunately Mars is also low in February, it is on the right in this figure. Notice how far below the blue line both of theses planets are. This blue line is the celestial equator – a projection of the earth’s equator into space. When Saturn crosses the meridian (a line passing through the north celestial pole and exactly south from your observing position) is will be around 17 degrees below the equator, contrast this with Jupiter that will be around 29 degrees above the equator earlier in the same evening. Of course if you live in the southern hemisphere both Saturn and Mars are well placed this year. Mars will have a diameter of around 9” at the start of the month rising to 11.5” by the end – still pretty small and challenging. In mid-April it will reach over 15” which will be a better time to observe it; it will also be around 33 degrees above the horizon by then.
Venus is also around in February for early risers as it is a morning planet. The chart below is for February 27th at around 6:20 am. Venus rise just before a thin crescent moon followed soon after by Mercury. Mercury will be hard to see as it is close to the Sun but Venus has an elongation of almost 44 degrees (this is the angle that is away from the Sun, the bigger the angle the better). If you wish to use optical aids to view Venus only do so before the Sun has risen. I would strongly caution against using any aids to look for Mercury. If you happen to even glimpse the Sun you will be blinded. I have included the ecliptic line again. Notice how the planets, the moon and the Sun are following the same line. As we are looking east now the equator is also inclined.
Whilst on the subject of planets I must mention the two asteroids shown on the figure above with Saturn and Mars. Both of these asteroids will be observable with modest telescopes although they can be tricky to recognise. Neither is visible to the naked eye as Vesta has a magnitude of just over 6 and Ceres just over 7. The best way to find them is to use some planetary software such as Stellarium (which was partly used to construct these figures). If you observe them on successive evenings and note their positions they will be seen to move against the stars.
I cannot leave this post with a mention of the supernova in the cigar galaxy, more correctly known as M82 (or NGC3034). This galaxy is situated in the constellation of Ursa Major and is very high at this time of year in the north east. At the time of writing the supernova is easily visible in even modest telescopes. I would very much like to have posted a picture of it but owing to the bad weather I simply have not had the opportunity to photograph it but you can see some excellent pictures here. I have caught clear views of it a few times between showers! It appears now to have reached its peak brightness of 10.5 mag (3rd Feb) but should still be visible through the early part of February. M82 is 11 to 12 million light years away. The supernova is a type 1a from its spectrum. This is a white dwarf that has been drawing matter from its large neighbour and reached an unstable mass and exploded with a truly massive release of energy. Do have a look for it. If you are a new observer M82 and the nearby M81 (or Bode’s galaxy) are well worth a look. The chart below shows how to find them.
It can be a little tricky because it is in a part of the sky with few stars and also because it is so far north equatorial mounts can be a bit difficult to manage (unless they are “go-to”). Alt-azimuth mounts do not have such problems. The simplest way is to draw an imaginary line between Phad and Dubhe in Ursa Major, then jump along that line the same distance again and M81 and M82 are just to the north of that line. Use your lowest power eyepiece to find them, on a reasonable night they can be seen with a 50 mm finderscope as well. But hurry it will not last for long!