Plain
Astronomy A Free Quarterly Magazine for the Salisbury Plain Observing Group
DIY Astronomy Make your own parallelogram mount Plain Astronomy
Volume 1 No. 1
Practical Observing The Eyes of the Owl Nebula An Evening in Somerford Boรถtes Rising The Flame & Horsehead Nebulae 1
Salisbury Plain Observing Group No fees, no agenda, no committee. Just sharing the sky. Salisbury Plain Observing Group affectionally as SPOG) is a group of astronomers who meet to photograph and enjoy the dark Salisbury Plain.
(known amateur observe, skies of
hour or so of each other, agreed to try and meet up, ideally at new Moon or when something astronomically interesting is in the sky. Since then the group has grown and we have almost 60 people on our email list who from time to time want to come out and observe.
The group began in 2009, when half a dozen or so astronomers met up at the Salisbury Star Party, and, realising that they lived within half an
We use Facebook to let our friends know what's going on, Twitter for announcements for observing details, and, primarily, email for alerts, not only for observing, but for astronomical events of interest. In 2011 our website was changed giving us more options for adding news and astronomy titbits. This magazine is the first we have produced and has some articles from the website, as well as some written specially. It‘s an experiment we hope will continue.
Plain
Astronomy DIY Astronomy Build your own Parallelogram mount .............. 3 Astronomy Lore Boötes Rising .......................................................... 7
SPOG uses easily accessible sites around the perimeter of the Plain; sites are used in rotation so that those living in the east are favoured as well as those in the west.
Deep Sky Observing The Eyes of the Owl ............................................. 5 Running the Marathon .......................................... 6 The Flame & The Horsehead ............................14
Although we are certainly not a club, Wiltshire does have three formal societies who offer both talks and observing sessions; the Wiltshire Astronomical Society meets at Seend each month from September to June; Swindon has Swindon Stargazers who meet in Lawn in Swindon, and Salisbury Astronomical Society meet at Winterbourne Earls. Just over the border in Somerset is Beckington Astronomical Society, and Bath Astronomers, also practical observers.
From the Eyepiece An Evening at Somerford ..................................... 9 AstroBasics Earth‘s Rotation & the Seasons ........................11 Bookshelf Guidebook to the Constellations ....................12 Cosmic Challenge ................................................12
The philosophy of SPOG is simple; all are welcome, especially beginners. There are no fees, no agenda, and no committee. The only rule is to enjoy sharing the sky.
Lunar Notes What to hunt for this month ............................13 The Solar Spot The Sun imaged ....................................................15 Noticeboard Local societies & diary dates .............................16
Cover image: “Hale-Bopp Over Stonehenge” used by kind permission of Philip Perkins www.astrocruise.com. Image © Philip Perkins 1997
A reminder of Comet 103P/Hartley photographed by Ian Pass from Bath October 2010
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DIY
Astronomy Last summer was my first as an amateur stargazer, and I confess I found it rather frustrating not having anything much to look at. So, in my usual fashion, I started to get Garage Project Syndrome and was looking for something to make.
If you have a little spare time, some practical skills, and a few materials, then why not have a go at Garry Keenor‘s parallelogram project.
like Mark‘s prototype - I needed the tripod fixing to screw in from underneath – I had to configure the bolt to be tensioned from above. I achieved this by adding a cutout to the main pivot upright which would hold the parallelogram arms. The tripod fixing would be achieved by means of a 3/8″ prong nut… or so I thought. Having been singularly unsuccessful at procuring one of these rare beasts – we‘re all metric now don‘tcha know – I hit upon the idea of trying my local camera shop. They sold me a 3/8″ nut which they use for displaying tripods in the shop for the princely sum of £3.
Then I visited fellow SPOGger Mark Radice, who had prototyped a binocular mount for his giant bins and showed how simple it was. Well, clearly this would not do – I had to try my hand at one. The starting point for my mount was the Skywatcher AZ4 mount I already own, which sits on a cheap but effective aluminium tripod. Being of Scottish descent I was not going to waste an existing tripod, so I took the mount off to check the fixing. I came to the conclusion that it was a standard 3/8″ tripod bolt sitting in a 60mm diameter well. I was wrong, but more on that anon…
So I took it home and checked the fit… errr, too tight. What‘s going on? Then the penny dropped. I took an M10 nut out of the cupboard, and it was a perfect fit. The lesson of this tale? Check your assumptions before you start work. A few days later and I had a bag of M10 prong nuts cheap as chips courtesy of ebay. I completed the tripod fitting and tested it out. It worked OK, but the first design had a relatively small contact area between the mount and the tripod.
I wanted my mount to solidly hold my 15×70 bins, which are a lot smaller than Mark‘s monster bins, but I also wanted to future-proof it against going larger at a later date. With this in mind I started work on the azimuth pivot, using 9mm ply sandwiched with pva glue. Since I didn‘t have the option of tensioning the Az pivot bolt from below
Once the mount was complete and loaded there was way too much movement due to temporary imbalances in the mount. So I added another
The finished mount with 15 x 70 binoculars attached
Garry’s altazimuth pivot with its Teflon furniture glides
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DIY ASTRONOMY
piece of 6mm plastic strip with a cutout. This engages with a bolt/wingnut assembly on the arms and locks the whole thing in the stowed position. So now you can load either bins or counterweights first safe in the knowledge that the mount won‘t move until you release the lock. It also means the p-mount is much easier to carry and load into the car.
donut of plywood so that the full width of plywood bore down against the top of the tripod well. This was much better. The lesson? Maximise the footprint of your mount if you are attaching to the tripod. The pivot itself comprises 3 teflon furniture glides screwed into the lower plywood disk, and a CD glued onto the upper. Teflon discs fit around the bolt and prevent the centre of the disc from being squeezed by the bolt tension. It works well – I was surprised at the amount of tension which I had to put on the bolt to eliminate slop, but the action is very smooth considering the ―Heath Robinson‖ approach.
All my counterweights are steel dumb-bell weights bought from my local fitness centre. The great thing about these is they use a standard 25mm hole, and come in a variety of different weights. I wanted to be able to fine-adjust the balance, so I routed a couple of slotted holes in the main arms and fashioned a weight holder block from wood. The weight spindle is the centre section of an old pair of bike drop handlebars – these have a standard 25mm diameter and are widely available through freecycle or your local tip.
For the parallelogram itself my over-engineering instincts kicked in and I procured some 3″ x 2″ oak from a local timber merchant. These would form the main load-bearing arms at the top of the paralellogram. The lower arms would be made of 1″ x 1″ oak and would be there to provide the parallelism – no load-bearing here.
The binocular head is designed to have 2 degrees of freedom, having both an Alt and an Az pivot. This allows for local adjustments in Azimuth so that you don‘t have to swing the whole mount to change direction. The binocular bracket itself uses a steel garage ―L‖ hanger bracket picked up from the local DIY store and cut down to size. This provides the right level of rigidity for the bins, and a simple plywood platform is bolted to it to provide a level surface. The Alt pivot is centred on the binocular‘s centre of gravity and means that it will stop wherever you place it.
The parallelogram bolts were standard M8 coach screws, but I used nylon washers between all moving surfaces – this gave a lovely smooth movement. A thumbnut on the upper central bearings provides a degree of tension adjustment, and all other bearings use nyloc nuts to ensure that nothing comes loose. One thing I tried to achieve was to avoid the difficult set-up which parallelogram mounts often have; being a counterweighted system, as soon as you load up one end the whole system becomes unbalanced and can tip over.
This was a really enjoyable build and has given me a very useful mount which comes into its own at star parties, where anyone can view an object regardless of their height. There are as many designs of p-mount as there are astronomers, so why not give it a go?
To combat this, the best way to set up is with the arms at maximum height/minimum extension. So I added a simple stowage lock mechanism using a
The mount in its folded position for transporting 4
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Deep Sky Observing
The Eyes of the Owl The Owl Nebula is an intriguing object, but a visual nemesis to many observers. Jonathan Gale gives some background and observing notes on this allegedly elusive object and its nearby galaxy
“A most intricate group of Of the four planetary nebula spiral arcs disposed around listed in the Messier two starry centres, looking catalogue, the Owl (M97) M97 Public domain image taken by like the visage of a monkey” Andre Fryns from http:// gives you two objects for the en.wikipedia.org/wiki/File:M97.jpg price of finding one; a nearby New deep sky observers often galaxy, M108, almost visible debate which of the Messier eyes of the Owl which I had not in the same field of view. objects is the hardest to locate seen before; the object remains
The Owl Nebula was first observed by Pierre Méchain in February 1781. Méchain was a contemporary of Messier and collaborated with him in hunting comets, discovering eight himself and co-discovering three. His was a major contribution to the Catalogue as thirty of the objects were due to his observations, and indeed he helped complete the final catalogue from 1779 to 1781. However, the Owl‘s name is again down to Lord Rosse who likened the dark patches to those of owl‘s eyes after sketching it in 1848; nevertheless one of his observing friends, TR Robinson, described the Owl as Plain Astronomy
Some have reported seeing it in 10 x 50 binoculars, but I have never done so. I first saw the Owl in 2009 at my first Messier Marathon through my 6‖ reflector; it was quite simple to locate appearing like a small smudge of cotton wool. I tried using binoculars, but I cannot recall succeeding. Nearly 2 years later, observing under the very dark skies of Devon with my 12‖ reflector, I detected the
Its distance from us is rather uncertain, but the figure of 3,300 light years seems the current acceptable estimate, with that distance deriving a diameter of 3 light years. Age is again uncertain with ranges from 6,000 to 12,000 years being quoted.
and the Owl is normally a candidate, which is odd as it is not really a difficult object to locate, given a brightness of magnitude 9.9. With enough aperture and dark skies, the real challenge is to be able to observe the ―eyes‖ of the Owl.
diffuse though with no contours visible, at least not in my telescope. Observing it very recently in the 12‖ again showed it fairly obviously, but although I was in a reasonably dark site, the light pollution was still too much to note the eyes. The Night Sky Observers Guide bears out the fact that the eyes are visible in a 12‖, but then they are no doubt observing from clear, dark skies in the depths of the USA! M108 first gets mentioned in Messier‘s observing notes when he re-observed the Owl following Méchain “nebula near the previous .. it is even fainter”
The Location of M108 and the Owl Nebula (M97)
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Wm. Herschel observing in 1789 noted that M108 was
Smaller apertures can show a faint bar of light, but 6‖ of aperture nails it. I first observed M108 during my second Messier marathon. It was reasonably obvious, once I had oriented myself after finding the Owl. A thin but definite slice of light appeared in the eyepiece when I slowly panned across from M97. I have also observed it in my 8‖ and once or twice in the 12‖.
“Very bright, much extended, resolvable … There is an unconnected pretty bright star in the middle”
The ―pretty bright star‖ was no doubt a 12th magnitude foreground star, which has a 14th magnitude companion, which is a challenge to resolve, although Leo Brenner (1855 – 1936), a now largely forgotten planetary observer, was able to resolve the companion with a 7‖ refractor. Brenner‘s observatory was on the island of Lošinj, which benefitted from steady, calm air in that part of the Adriatic. However, not all Brenner‘s observations were quite as faithful; his maps of Mars apparently showed a maze of canals, following Percival Lowell, although it was confirmed that he had indeed observed the moons of Mars.
As the Plough rises in the spring sky, why not spend a little time hunting for the Owl and M108—better still, come along to the WAS Messier Marathon on Saturday 24th March and have a hunt for them all!
Running the Marathon A Messier Marathon is an attempt to find as many Messier objects as possible in one night. The optimum time is around mid to the end of Charles Messier (Public March, although depending on the domain image) observer‘s location, there will be a different number visible. In the UK most objects are not too difficult, but the southern-most ones and early evening/morning ones obviously present the greatest challenge.
This galaxy should have been M98, but despite making a note to this effect, Messier changed his mind and excluded it from the final catalogue. It wasn‘t until 1953 that it was included by Owen Gingerich under its final number. M108 is around 45 billion years distant with a diameter of around 100,000 light years. It is edge on so is difficult to classify but is thought to be a barred spiral. It has a magnitude of 10, but its surface brightness is amongst the lowest in the catalogue at mag 21.9.
The Virgo cluster presents a challenge to most observers with the sheer number of galaxies observable within that region along with Coma Berenices. A good map is essential; Sky and Telescope‘s Pocket Sky Atlas (PSA) is the standard work for most observers and is ideal for a marathon. The PSA also has a close up map of the Virgo region which makes navigation easier. The internet is an excellent source of guides and information; The Ultimate Messier Observing Log is an excellent site offering either software or a set of printed maps, or try Larry McNeish's Messier Marathon Planner.
A Messier Marathon is a fun event, but to make it a little more challenging, you could limit the telescopes to no more than 4‖ aperture or outlaw GOTO telescopes to truly follow the Messier spirit! Whatever you use, why not have a go at the Marathon and follow a great observer‘s footsteps.
M97 & M108 sketches by Mark Radice
Web References Larry McNeish : http://members.shaw.ca/rlmcnish/darksky/messierplanner.htm The Ultimate Messier Object Log: http://members.shaw.ca/rlmcnish/darksky/messierplanner.htm
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BOÖTES
As Boötes returns to the spring skies, Dawn Wilson recounts the myths linked to the constellation and some of the sights to observe within.
R I S I N G
Boötes is rising again in the spring skies, and is an often overlooked constellation. Whilst it may not contain conspicuous deep sky objects, it does hold many interesting double stars for the observer.
The name Boötes is derived from the Greek for herdsman or ploughman and was one of 48 constellations described by the 2nd century astronomer Ptolemy; it now remains one of the 88 modern constellations and contains the fourth brightest star in the sky Arcturus, at is southernmost point. Boötes is said to be one of the most ancient constellations in the sky. There is no single myth associated with this constellation. It seems to have impressed early civilizations with its resemblance to a human torso (a kite-like shape, sometimes with legs or a raised arm). The most ancient associations from the area of the eastern Mediterranean and Middle East are that of herdsman, cart driver, and ploughman.
Exactly whom Boötes is supposed to represent in Greek mythology is not clear. In Greek literature, Boötes is mentioned in Homer's Odyssey in a long and complicated multi-generational story of intrigue. The story starts with newborn twins, whose father was Poseidon, who were abandoned on Mt. Pelion to die and later rescued and raised by a herdsman. One of the twins was named Boeotus and went on to be reclaimed by his maternal grandfather and to inherit part of his kingdom.
An Egyptian legend saw Boötes as a guardian goddess in the form of a Hippopotamus who kept the evil pole stars under control. An Arab legend saw the same pole stars as a flock of sheep herded by Boötes.
According to another version, he was a ploughman who drove the oxen in the constellation Ursa Major using his two dogs Chara and Asterion (from the constellation Canes Venatici). The oxen were tied to the polar axis and so the action of Boötes kept the heavens in constant rotation
In a completely different interpretation, ancient Chinese astronomers also placed significance on Arcturus. They saw the star as one of the horns of a giant dragon in a large constellation that stretched from Boötes to the constellation Virgo. The full moon appearing near Arcturus was a sign of the new Chinese year.
In another version Boötes was also supposed to have invented the plough. This is said to have greatly pleased Ceres, the goddess of agriculture who asked Jupiter to give Boötes a permanent fixture in the heavens as a reward for doing this.
In ancient Babylon the stars of Boötes were known as SHU.PA. They were apparently depicted as the god Enlil, who was the leader of the Babylonian pantheon and special patron of farmers.
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Boötes as depicted in Urania’a Mirror. Public domain image.
Another version portrays Boötes as a grape grower called Icarius, who one day invited the Roman god Bacchus, also called Dionysus, to inspect his vineyards. Bacchus revealed the secret 7
BOÖTES R I S I N G
Deep-sky objects in Boötes
of wine making to Icarius, who was so impressed by this alcoholic beverage that he invited his friends round to sample it. Having never tasted wine before, they all drank too much and woke up the next morning with terrible hangovers; and they made the mistaken assumption that Icarius had tried to poison them. It was decided that Icarius should pay the price with his own life, and he was swiftly murdered in his sleep. Bacchus placed Icarius in the stars to honour him.
Herschel recorded 113 galaxies in this constellation, although most are unremarkable for visual observers. Aside from the ones below, others of interest are NGCs 5529 and 5673. NGC 5248 is a compact spiral galaxy lying some 59 million light years away. 8‖ to 10‖ telescopes show a bright nucleus surrounded by a fairly bright oval halo.
Following another reading the constellation is identified with Arcas, son of Zeus and Callisto. Arcas was brought up by his maternal grandfather Lycaon, to whom one day Zeus went and had a meal. To verify that the guest was really the king of the gods, Lycaon killed his grandson and prepared a meal made from his flesh. Zeus noticed and became very angry, transforming Lycaon into a wolf and gave back life to his son. In the meantime Callisto had been transformed into a she-bear, by Zeus' wife, Hera, who was angry at Zeus' infidelity. When he was grown up, Arcas met with the shebear and, since obviously he didn't recognize her as his mother, he began to chase Callisto. Callisto, followed by Arcas, sheltered herself in a temple, a sacred place whose profaners were convicted to death. To avoid such fate, Zeus decided to set them in the sky, Arcas as Boötes and Callisto as Ursa Major. This is a rare version of the myth surrounding Ursa Major, as the myth usually holds that Arcas is transformed into a bear as well (becoming Ursa Minor), and in such versions Boötes has no part. Ursa Minor, and Ursa Major, are constellations whose identification only originated in later classical Greece, and in Rome, and as such Boötes kept separate associations dating from much earlier.
NGC 5466 is a loose globular cluster, some 6‘ in diameter that can be observed with most telescopes. It was discovered by William Herschel on May 17, 1784. Observations through 8‖/10‖ scopes show an unevenly mottled core with the an east-west elongation. The Boötes void, a large section of the universe mostly devoid of galaxies, is located in the area of Boötes. It is some 250 million light years in diameter with the centre some 700 million loight years from Earth.
Noteable Stars Kappa Boötis is a beautiful double star with a bright, white primary and a bluish secondary. Easily visible in a small scope at 75x. Epsilon Boötis is a lovely double of golden yellow and greenish stars. Try 175x with a smaller scope. Iota Boötis is a wide double suited to binoculars or a smaller telescope. Its two bright components are yellowish and bluish. Try 75x with a 4‖ to 6‖ telescope.
In Ovid's Metamorphoses VIII, Icarus is told by his father Daedalus, upon receiving the wings, to fly using the Boötes and Orion as guides. Icarus ignores the advice to run this "middle path" and subsequently drowns. References: Chandra X-ray Observatory website and Wikipedia.
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From the Eyepiece Here‘s a round up of reports from practical observers who are observing for fun, following a program, or choosing to specialise in an observing discipline
Image source : http://en.wikipedia.org/wiki/ Image:Astronomy_Amateur_3_V2.jpg taken by user Halfblue
running before I had got half of my gear from the car! After doing my set ups I was ready for the public at 7:25pm. By now about 15 people had turned up ready for the evening and were being briefed about the evening‘s events. I could not get Uranus as it was behind a tree so I started on Venus and noticed it about 55% lit, while viewing this planet the first group of people turned up. I just asked them what they would like to look at and we would go from there, as different groups came over I went back to the more popular objects like Jupiter, M42 (Great Orion Nebula) and M31, the Andromeda Galaxy. I could not do Mars yet as that planet was behind a tree, just like Uranus but in the other direction! John Arthurs could go and view Mars as his equipment was fully portable, one advantage of ‗Grab and Go‘ kit! I decided to M52 in Cassiopeia. Public stay with Messier domain image from 2MASS/ objects as these NASA were the brighter objects in the sky. During the night we looked at M42 in Orion, M41 a nice open cluster just below Sirius, M31 followed by M32. At this time I was starting to get concerned as it started to rain, I had not noticed that both Jupiter and Venus had disappeared! What shall I do, put the kit away or
Jon Gale asked me to help out at the Somerford Gazers observing meeting which was held in the village of Little Somerford just off the B4042 Brinkworth to Malmesbury road. I went along last year to help out, but instead of showing people the night sky we had to do talks as the sky was completely covered in cloud, this year was different though, the sky was clear! They have been having this annual meeting for the past five years and this was going to be the first viewing session, I guess the previous four had been hit with cloudy weather? As John Arthurs was starting to show more interest in viewing sessions I brought him along to help out, as we did not know how many people were going to turn up. The meeting was due to start at 7:30pm, so I told John to be at my house by 6:45pm so we could be there well in advance of the start time, this would give us time to set up our gear ready for the public. When I arrived at just past 7pm, Jon was already set up and viewing! His night vision (if he had any) disappeared as I drove into the farmers drive way and noticed him in my main beam. After parking up the car, Jon introduced me to Gordon (the owner whose land we were going to be using tonight) and Dr Mike Jones, the village‘s resident astronomer, who arranges these meeting with Jon.
After looking around the venue, John and I decided we would set up on a hard standing with a good view of the south, Jon was going to be in the main garden with views to the west. Tonight I was going to use my trusted Meade LX90 and John was going to use a four inch refractor mounted on a tripod. Jon was using his 12 inch Dobsonian and a pair of 15x70 binoculars mounted on a tripod. As usual John was up and Plain Astronomy
Public outreach can very rewarding. Recently SPOG members journeyed to the north of Wiltshire to help out at a village observing event. Peter Chappell describes the evening and the objects we observed.
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From the Eyepiece
hope it was only a short shower? By now I could see Venus coming through the clouds, so I went back to the car and brought the brolly out and covered the telescope to the best I could. The shower only lasted about five minutes and nothing looked like it got that wet, so I carried on like nothing had happened. I got a few wow‘s when I showed people a few open clusters, namely M34, M37 and M38. The Pleiades (M45) was a popular choice for the public; I told them that it might be better to view this with the M42 by Nick Howes and reproduced Spotter Scope as by permission the field of view for the LX90 would not show all the cluster. I also showed people, M52 in Cassiopeia before heading out of our galaxy and looking at M81 and M82 in Ursa Major. After looking at Messier objects I showed people different coloured stars, we looked at the yellow of Capella in Auriga, the red of Aldebaran in Taurus, the blue of Rigel in Orion and finally the white/blue of Sirius in Canis Major. This also got some good reactions from the people viewing the objects. I was now having trouble with a security light on a house a few doors down the road, with this affecting our night vision we all went to Jon‘s location which was behind a hedge in the main garden. At the time Jon‘s massive Dobsonian was pointing at M97 (the Owl Nebula or Peter‘s nemesis!), I could make the Owl out quite clearly, does help to have a large scope around!
Earlier on I was talking to some people about the telescopes they had, one couple said they had recently brought a Celestron Nexstar SE6 and was having trouble using it; as they had brought it along I said I would try and help them out even though I have never controlled a Celestron scope in my life. They were setting up the scope by going to three unnamed stars manually, this I found very strange? After looking at the hand controller I noticed the wording ‗Sky Align‘ after having a think for a while I
came to the idea that there was a star alignment system within the telescope. Once they had done three star manual alignment, I took charge of the hand controller and hopefully would help them out. I explained about the buttons and the sub menus on them. I had trouble trying to go to a Messier object, every time I hit the ‗M‘ button it came up with 110. Putting in my own choice I could not get the scope to work, turned out if I wanted a number below 100 I had to go 0 and then the number I wanted, totally different to the Meade hand controller! After we had sorted out this little problem we found M42 in the eyepiece, much to the delight of the owners. I also showed them how to find NGC 457 (the Owl Cluster) in Cassiopeia, it took them a few seconds to find the Owl, and they could not make out its wings but once they had founds its wings everything fell in to place. After playing around for a while I left the happy couple to get on and try finding new objects to view. This did not last very long as the batteries within the telescope were going flat, told them it might be a good idea to get an external power supply, that way you will be able to view for
Hubble’s Variable Nebula. Public domain image by HST/ en:NASA/en:JPL.
much longer especially if the weather was cold, like it was tonight! By now the security light had gone off, so I went back to my own telescope and had looked at M65 and M66 in Leo. Mars was well clear of the tree that stopped me viewing this planet earlier on, I 10
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think I could make out Syrtis Major? I did have a small viewing list to look at myself, I decided not to carry on with the Herschel 400 but to view objects within Monoceros, the Unicorn. The only Messier object in this constellation is M50, this is an open cluster with mainly white/blue stars. The next four objects are on the Caldwell list, namely C49, C50, C46 and C39. The Rosette Nebula, C49 I could not make out, probably better if imaged. I could make out C50 or NGC 2244, another nice open cluster. The other two objects C46 (Hubble‘s Variable Nebula) and C39 (Eskimo Nebula) I could make out quite well!
a polar cap, neither John nor I could make this out, even putting on a bigger eye piece, namely an Ethos 13mm! I asked Jon to try and find the Horsehead or B33 in Orion, putting the Hydrogen Beta filter on the eye piece to help bring out this hard item to see, although we could not see it; probably the sky was not dark enough to bring it out.
That was it with my telescope for the evening, time to go back and see what was happening with Jon in the garden. By now, we were down to about five people and Mars had cleared the hedge. We could make out Syrtis Major quite clearly, does help having bigger aperture! Jon said he could make out
Did you see the mistake I made earlier on? Well I said I would be viewing objects in Monoceros, the Eskimo Nebula is in Gemini!
Astronomy, the Ear th’s Rotation and the Seasons All of the stars and planets in the night sky appear to move as the night progresses, but they don’t. In fact, this apparent movement is due to the rotation of the earth on its axis – the same rotation that causes the sun to move in the daytime sky. Over the course of one hour the earth rotates 15 degrees on its axis, and so the stars appear to move 15 degrees. For comparison, the full moon occupies about ½ a degree. So the stars and planets rise in the East, and set in the West. They all rotate in an anti-clockwise direction about a point known as the celestial pole - an imaginary point directly above the earth’s north pole. For those of us in the Northern hemisphere, there is a star which happens to be almost exactly at this point. Polaris or the Pole Star is in Ursa Minor - the Little Bear - and all other objects appear to rotate around this one.
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By now it was 10:45pm and the last of the public was leaving, so we decided to pack up and go home as well. Not before clearing the ice from my car!
L
Objects near to the Pole Star are always visible from the Northern hemisphere – they never rise or set and can be seen all year round. These objects are known as circumpolar. The bright star Vega in the constellation of Lyra is just circumpolar, and never quite sets.
As the moon moves in its orbit its position relative to the sun changes, causing different parts of the moon’s earthward face to be lit. This gives rise to the familiar phases of the moon
Those objects which are not circumpolar are seasonal, and so are only visible at certain times of the year. This is because for much of the year, they occupy the same area of the sky as the Sun, and so are drowned out by the glare of daylight. Becoming familiar with the visibility of constellations and objects as the seasons progress is one of the many delights of astronomy.
It is important for an amateur stargazer to understand this rhythm, because – apart from being a fascinating subject in itself – it governs the best times for stargazing. In the two weeks between first and third quarter moon, the brightness of the moon is such that all but the brightest objects are rendered faint or even invisible, regardless of the quality of your telescope. Indeed, the brightness of the moon at these times can even be a problem for those observing the moon itself, necessitating the use of filters to reduce the glare.
The Phases of the Moon The moon orbits around the earth, with an orbital period of around 28 days. The moon rotates about its axis just as the earth does, but due to the phenomenon of tidal locking the moon’s rotational period and its orbital period are the same, 28 days. This means that the same hemisphere of the moon is always facing the earth, giving the moon a constant “face” as viewed from the earth.
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Bookshelf
Reviews of books, both old and new, on all aspects of astronomy
Cosmic Challenge by Phil Harrington
Guidebook to the Constellations
488pp. Cambridge £28.00
Phil Simpson
Although published over a year ago, this book has become one of my most thumbed and referred to. Phil Harrington is a well respected deep sky author and his latest book gives over 500 objects spread over 178 challenges.
863pp. Springer £31.99
Each year I visit AstroFest, I head not to the equipment but the books. This year I had earmarked 2 or 3 new titles to get, but I‘d already acquired them by the time the event came round. Just as well really as I might not otherwise have purchased ―Guidebook to the Constellations‖, Whilst I have many observing guides, there was space for a book that had constellation lore in it as well as details on the objects. This book fits the bill.
I was introduced to this book in January 2011 and it absorbed three of us during an astronomical observing holiday. The chapters are divided into naked eye, binocular and large binocular, and then small, moderate and giant telescope challenges. The deep sky is well catered for with targets from M3 (naked eye) to Copeland‘s Septet for the monster scopes. The Moon is well covered along with some planetary challenges. Sketches are also included which aim to depict the view through the eyepiece. Mostly they succeed, but some are very dark indeed and it is a challenge to see the sketch at all!
Rather than taking each constellation in isolation, the author has grouped those together which share common origins and myths to tell the tales and which can then be learned as a unit. Key star names and their pronunciation are also included, along with constellation maps and tables of objects. There are plenty of images, all taken by amateurs, and, interestingly, many are shown both in their original format and processed to give the appearance in a medium sized telescope.
Some objects will be very familiar to the experienced observer, but it is the challenge of using smaller optics or indeed the naked eye alone, which is the draw to this book. For those with very large apertures (15‖+), the book covers some esoteric objects which will keep one occupied for many sessions.
It is a weighty book to wade through, but at the price and number of pages, it seems good value and very informative for those who want a single reference to the constellations and their objects.
In summary, an excellent astronomical reference to hone your observing skills, given the dark skies and patience to do so.
Jonathan Gale is an avid collector of astronomical texts, particularly sky atlases and deep sky references.
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LUNAR NOTES
Whilst many at SPOG are deep sky observers, the Moon always presents an interesting observing target each month. Here‘s a few lunar challenges to look for over the coming months.
During the lighter months, the moon is still there to provide some observing challenges, you could try the Lunar 100 or look for features such as the Werner X. Werner‘s X was first publicised in 2004 in the Canadian magazine SkyNews by an amateur astronomer. The X is visible on day 7 of the waxing Moon‘s phase along the terminator. It‘s caused by the convergence of 4 craters; Purbach to the east, Blanchinus to the west, La Caille and Regiomontanus north and south respectively.
Lunar V, which I have not yet observed. The V is sandwiched between Mare Vaporum to its north and Sinus Medii to its south. The effect is created by low angled sunlight shining across several small craters. The Lunar V is apparently as obvious as the Lunar X, although it has not attracted as much attention amongst observers. Having observed the X and V, why not have a go at Plato‘s craterlets? Plato is an obvious crater siting on the edge of the Mare Imbrium. It is easy to find and recognise as it shows no central peak or rough floor, untypical of an impact crater.
Werner is a crater which lies to the south west of the X formation; it is named after the 15th century German astronomer and mathematician Johannes Werner.
Werner’s X by Andy Burns
Although the crater does not directly contribute to the X effect, it is the closest well lit crater and acts as a signpost to locating the effect. I first observed it with my small reflector whilst casually scanning along the terminator; a case of the right place at the right time!
Lunar Image by Jonathan Gale
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Together with the Lunar X is the 13
Plato. Public domain image released by Tom Ruen
There are some 16 craterlets to locate on the floor of Plato, of which the largest ought to be able to seen in 4‖ to 6‖ of aperture, with 8‖ for the smallest. This is based on reports and background reading and research. So whilst the days are longer and the nights lighter, revisit the moon and have a go at these lunar challenges.
Observing the Horsehead and Flame Nebulae in Orion Wiltshire‘s dark skies allow us to observe some of tougher objects in the night sky. Mark Radice describes a winter‘s night observing two of them.
It is always a pleasure to enjoy a warm spring nights observing after a cold winter. As the warmer and lighter evenings move in, though, Horsehead Nebula. Public Domain image from NASA it is always tinged with the fact that observing will become limited and eventually has to stop notes a challenge. It was so windy that the dobs once the summer is here. would weathercock with the wind if left unattended for a few minutes! As this weather changes, I use it to reflect on the recent observing achievements coupled with what will now have to wait another year.
IC 434, the faint nebulosity against which the horsehead is silhouetted was first seen through Jonathan Gale‘s 12‖ Skywatcher Dobsonian with a Lumicon H-B filter. The background nebulosity was clearly visible in the eyepiece and there, superimposed on it, was that elusive notch of the horsehead. As making a sketch was intolerable due to the strong wind, I noted the stars in the eyepiece against the charts in the S&T Pocket Sky Atlas and made a sketch from memory the following morning. I think it took me several hours to defrost after that night!
I try and have a handful of target objects that I hope to observe each season. Any more than a handful is often too much for our unpredictable skies and my work/family constraints. Two objects that have featured on my winter wish list for some time is the flame nebula NGC2024 and IC434 and the adjacent horsehead nebula, Barnard 33. Having read about these interesting objects – and noting that they are not easy objects to observe by any means – I hoped to observe them under our dark skies on Salisbury Plain.
We returned to Salisbury Plain at the next new moon and repeated the observation. Thankfully
It was winter 2011/12 that I finally managed to observe these objects and on two separate occasions. Both observations were made under the cold but dark skies of Salisbury Plain and through a variety of instruments. These objects are challenging as they require good optics and an experienced eye but most importantly of all they require a dark sky. The malingering effect of light pollution rob these faint objects of any contrast rendering them indistinguishable from the background sky. As a result, I didn‘t even bother from my home observatory in Amesbury as the nearby streetlights would be too over whelming. The first observation was made on a bitterly cold night with a hard frost. The puddles at the observing site were frozen solid and the ground was as hard as concrete. This was coupled with a vicious, northerly cold wind that burnt through any gaps in clothing and made referring to or making 14
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nearby trees sheltered us from the strong wind so I could make a sketch without my notes scattering everywhere. Garry Keenor had brought his 10‖ dob and, again with the H-B filter, IC434 and the elusive notch were readily visible – albeit obviously fainter than through the 12‖.
On the same night (the first windy night) I also observed the flame nebula through my 100mm binoscope at x30 atop a homebuilt parallelogram mount. What was first noticed was the incredibly bright star of Alnitak. This bright star has to be moved from the field of view to make the nebula easier to see. The nebula is not bright by any means but the contrast between it and its two dark lanes running through it catch the eye. It is only then that you realise there is a tenuous region of nebulosity in the field of view. Although I did not make a sketch that night due to the wind, I did repeat the observation later in the month at the Tilshead observing site. The Flame nebula is surprisingly hard to sketch as bright Alnitak washes out the faint nebulosity making it hard to trace its outline. Secondly, even the faintest red light deteriorates one‘s night vision enough to render the Flame hard to see for a few moments. These objects were quite a challenge to observe but, under clear dark skies, not impossibly so. It just goes to show that patience and practice make all the difference but the biggest factor has got be having access to dark skies with a good horizon.
The Solar Spot
Not all astronomy is done at night! Solar astronomy is becoming increasingly popular using specially built and filtered telescopes for imaging. Some of the group have such scopes, but always remember : NEVER, NEVER LOOK AT THE SUN USING A TELESCOPE, BINOCULARS OR ANY OPTICAL AID! IT ONLY TAKES A MICROSECOND FOR THE SUN TO DESTROY YOUR EYESIGHT!
Solar image by Andy Burns, Chair of Wiltshire Astronomical Society taken 11th March 2012. Andy's comments: ‖Crackling sunspots 1430 and 1429 are departing the near surface, but massive streaks of plasma cross the surface.‖ Plain Astronomy
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Noticeboard
Diary - April to June April
Wiltshire has a wealth of astronomical opportunities; here‘s how to access them, together with a few over the border in Somerset as well.
Saturday 15th — Saturn will be at its closest approach to Earth and its face will be fully illuminated by the Sun. This is the best time to view and photograph Saturn and its moons. Saturday 21st — New Moon & Lyrids Meteor shower. The Lyrids usually produce about 20 meteors per hour at their peak, producing bright dust trails that may last for several seconds. With no moon this may well be a good shower.
Local Societies The Wiltshire Astronomical Society is a thriving, friendly club catering for all aspects of astronomy, from armchair to practical, visual to imaging. We meet monthly at Seend for talks by both national and local speakers, with observing sessions held at Lacock. www.wasnet.co.uk
May Sunday 20th— New Moon
June
Swindon Stargazers hold monthly meetings for talks by members and external speakers in the Lawn Community Centre, Lawn Swindon, with observing evenings at a variety of sights organised as and how the weather permits. www.swindonstargazers.com
Tuesday 5th ~ Wednesday 6th—Transit of Venus which from Wiltshire (cloud permitting) will be visible at sunrise as a partial transit. We‘ll probably be meeting either at West Kennett Long Barrow, or the Sanctuary Car Park a little further along.
Beckington Astronomical Society is aimed at anyone with an interest in astronomy and space sciences; talks are held monthly with a beginners item and a main talk exploring a topic in more depth. The meeting venue is Beckington Baptist Church Hall. www.beckingtonas.org
Tuesday 19th — New Moon
National Events Spring Star Party
Salisbury Astronomical Society welcomes anyone with an interest in astronomy. You do not need to own a telescope or binoculars, the society has a wide selection for you to have a hands on try before you invest any money in purchasing equipment. Meetings are on the first Thursday of each month at Winterbourne Earls and we also have a viewing area at Old Sarum Airfield.
19th to 23rd April at Kelling Heath, Norfolk www.starparty.org Webb Society AGM
16th June at Institute of Astronomy, Cambridge www.webbdeepsky.com
The Herschel Museum, Bath is dedicated to the many achievements of the Herschels, who were distinguished astronomers and talented musicians. It was in 1781 that William Herschel discovered Uranus from here. www.bath-preservation-trust.org.uk/?id=8
Contact Details
Bath Astronomers is a community of amateur astronomers who live in and around Bath. The group is now the observing section of the William Herschel Society. Bath Astronomers aims to get local observers together for discussion and observing. www.bathastronomers.co.uk
Website
www.spogastro.co.uk
spogastro@googlemail.com
http://twitter.com/SPOGAstro
http://www.facebook.com/group.php?gid=119305144780224
Cover image: “Hale-Bopp Over Stonehenge” used by kind permission of Philip Perkins www.astrocruise.com. Image © Philip Perkins 1997
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