Guide to Observing the Best Deep Sky Objects through the Year

Transcription

1 Guide to Observing the Best Deep Sky Objects through the Year David Geary Introduction I brought my first scope almost 20 years ago. I was working as a Park Ranger at the time and thought it would be a good idea to run some public viewing sessions, or star parties, as they re colloquially called. Hence the emphasis throughout this guide on running events. Another theme I ve focussed on is selecting the very best deep sky objects. Obviously you ll want to show off the best the night sky has to offer if you re holding a star party, especially as people tend to have very high expectations after looking at images from the Hubble Space Telescope. Another reason for choosing the best objects is that they re often the brightest, and can therefore be seen in light polluted skies, plus they can be found more easily. After having a break from astronomy, I ve only been seriously into deep sky observing for a couple of years. I m still something of a novice, which I hope has enabled me to anticipate exactly what a beginner will need to know. (Well perhaps not an absolute beginner. Maybe you need to know a little already in order to benefit the most from reading this.) The following information has been included. Tips on how to find objects, such as where they are in relation to nearby constellations and what to look for in the finder scope. The chart number of different objects in the Cambridge Star Atlas. Exactly when it gets dark to help plan events. What to expect to see, to help people decide what they want to look at next. Plus it should help confirm you re looking at the right object, and be interesting to compare results. What eyepieces to use. Not so much which make, just which magnification and field of view are best. For nebulae, which filters produce the best results. (Sometimes it s no filter at all.) This might be quite useful if you re thinking about buying some light pollution filters. 1

2 (The bottom three may vary depending on what scope you re using. For example, a smaller scope may be better with a UHC rather than OIII filter as it does not collect so much light.) One of the reasons I ve written this is so I don t forget everything I ve learnt over the past year! I hope this will be of use to other amateur astronomers too. Many thanks to Damian Briden from the Rosliston Astronomy Group for proof reading this and providing extra comments where a little more experience was needed. The Rangers entertain people with the Park. We entertain people with the night sky and a telescope. John Dobson (the inventor of the Dobsonian Telescope) speaking on touring America s National Parks. Tips for Deep Sky Observing 1. Observe on a moonless night. 2. Wait long enough after sunset for the sky to turn truly dark. At the end of June, this will be almost 1am. 3. Allow at least half an hour for your eyes to adapt to the dark, then avoid light sources. (Red torches are ok.) 4. Observe your chosen target when it s high in the sky here the sky is much darker and the amount of atmosphere you are looking through thinner. This factor is really important. 5. Wait until nearby lights have been turned off. Obviously most people go to bed by about 11 and turn off their lights. Some street lights are also turned off now, to save electricity, at some point after midnight. 6. Try to find an observing place hidden from the direct glare of lights consider the use of a black cloth (like a Victorian photographer as a shroud) to shield you at the eyepiece. 7. Use averted vision. That is, look a little off to the side, and the object will appear brighter. This is due to the anatomy of the eye. For a further explanation, try doing a search on the internet for averted vision rods and cones. 8. Your eyes are sensitive to movement even in low light levels. If you re observing an object right on the edge of visibility, try moving the telescope slightly, or tapping gently on the diagonal if your scope uses one. 9. Get the biggest scope that s practical at least 8-10 inches for a mirror based telescope, and at least 14 inches if you re more serious.* 2

3 *Remember though that a small telescope on a good quality mount will show more than a big telescope on a wobbly one. A small telescope fits easily into a car to be taken on holiday to a dark site. Also the best telescope is the one that you actually want to drag outside and use and not the beast that you find excuses not to! 10. Travel to a darker location. There is some benefit in traveling a few miles into the countryside, but you ll need to go somewhere truly dark, like Exmoor or the Yorkshire Dales to see a real difference. 11. If you don t have a GoTo system, use a star atlas and red LED torch to find what you re looking for. I prefer The Cambridge Star Atlas because it has white pages that can therefore be written on. Don t forget that your phone can become a powerful observing tool with the use of astronomy apps. A highly regarded one is SkySafari 5. Also get a laminated Philips planisphere. Skymaps.com also provide clear monthly printable charts, they are free as well! If you ever have difficulty locating an object, Google the name along with the word constellation, then click on images. Don t forget the free planetarium Stellarium, available for PC and Mac this can really help you learn your way around the night sky even before you venture out in the dark! 12. Make your observations on a night with very good transparency. That is, when there is absolutely no cloud or mist (we often get very clear conditions soon after a wet weather front has passed). Hazy conditions develop when the air is still, and may even allow better views of planets, but not deep sky objects. My Setup I m observing from the edge of a town in the East Midlands, and I can see about four stars within the Square of Pegasus, which rates the sky darkness in my area as average. I use a 16 inch f/5 truss tube Dob with a Telrad finder and a more traditional 9x50 finder scope. I prefer the RACI (right angle correct image) finder scopes. As long as you observe objects when they re high in the sky, it should be possible to see most of the objects mentioned with a 10 inch scope. The list of best targets for a smaller scope will be a little different from this list however. Unless you have a really dark sky, it may not be worth looking at some of the fainter objects with a small telescope. But on a positive note, a smaller scope allows a greater area of sky to be observed through the eyepiece (due to its shorter 3

4 focal ratio which results in less magnification). You ll probably find that a few of the larger open star clusters fit in the field of view better with such instruments or binoculars. They include M45 (the Pleiades,) M44 (Praesepe or the Beehive Cluster,) and Cr399 (the Coat Hanger asterism.) Listed below are the eyepieces I used for the observations. If you need to know which eyepieces would produce the same magnification and true field of view in your own scope, you can use the field of view (FOV) Calculator on the Sky At Night website. Focal Length Mag Apparent FOV True FOV 35mm 60x mm 80x mm 155x mm 250x From top to bottom, the eyepieces are a Skywatcher Aero ED, Meade Super Plossl, Vixen LVW and Televue Radian. The telescope is made by Nottingham based telescope maker, David Lukehurst and has mirrors with standard protected aluminium coatings. The primary mirror is 1/10 wave and the secondary is unspecified. (That s just how Oldham Optical supply their mirrors.) January to March Winter is definitely the season for open star clusters, plus the Orion Nebula is just superb. At this time of year, if there are any planets around they re more likely to be high in the sky, which makes them clearer. So despite the cold, winter is a good time for star parties. Open star clusters are quite bright and can still be seen when the sky it not at its darkest. So you could plan any public viewing sessions while the moon is in first quarter (and therefore visible in the evening sky.) The slight loss of darkness is a trade-off that s worth making in order to see the craters on the moon. However, if you want to see all of the details below, pick a moonless night. 4

5 Month Start observing Fully dark Start of January 5.00pm 5.45pm End of January 5.30pm 6.15pm Start of February 6.00pm 6.45pm End of February 6.30pm 7.15pm Start of March 7.00pm 7.45pm End of March 7.30pm 8.15pm British Summer Time begins Very end of March 8.30pm 9.15pm Nebulae M42 The Orion Nebula in Orion Chart 9 Of all the nebulae that can be observed over the course of a year, M42 is by far the best. You can just make out a smudge with the naked eye if you know where to look. It s easily visible in the finder scope, and fits snugly into the FOV in the 26mm eyepiece. There s a C shape formed by four stars in the centre. Using the C shape as a guide, a dark area can be seen in the upper right of the nebula, plus another in the upper left. There s also a gap in the nebulosity around the four stars that form the C shape. Both above and to the left of the C, mottling is visible. Arcs of glowing dust and gas can be seen coming away from the front of the C, so the whole thing looks like a right hand holding a bow. Some distance away from the main nebula there s a bright star in a 4 O clock direction*, which has some nebulosity around it too. A light pollution filter doesn t reveal any more detail and just makes everything green, so it s best viewed without one. * Note that views and directions in telescopes vary depending upon optical type and the use of a star diagonal; mirror reversed and upside down, etc. Know your telescope to help you orientate yourself. Some planetariums (SkySafari for example), allow you to modify the view to match the view you see through the eyepiece with the simple press of an on-screen button this can be VERY useful! M76 The Little Dumbbell in Cassiopeia Chart 2 or 7 Find the Little Dumbbell using the Telrad and nearby stars, it s not obvious in the finder scope. It s best viewed through the 26mm eyepiece with no filter. The nebula is quite small and elongated. You can just make out it s narrower in the middle. It s not mind blowingly impressive but at least you can see it. 5

6 Other Nebulae The other nebulae in the vicinity are more difficult to observe. The Crab Nebula is worth a look using a light pollution filter, but is only a smudge. The Horsehead is notoriously difficult to observe, requiring clear and dark skies, well collimated large optics and the use of a Hydrogen Beta Filter. The Rosette can be view when conditions are optimal (with filter) though. Even when conditions are not brilliant, the bright star cluster embedded within the Rosette is worth tracking down! Open Star Clusters The Perseus Double Cluster NGC 884 and 869 in Perseus, towards Cassiopeia Chart 2 To find the Perseus Cluster, hop between two of the stars in Cassiopeia, and keep on going for about two and a half times that distance towards Perseus. Again, it is visible as a light smudge under dark skies without optical aid. You ll see it in the finder scope easily. It fits into the FOV with the 35mm eyepiece with room to spare. One half of the cluster has a C shape formed by five stars. In front of the C is a bright star, and in front of this there seems to be an explosion of stars in a funnel shape coming out from the star. The Perseus Double Star Cluster is the finest open cluster in the sky. The Owl Cluster NGC 457 (aka the Dragonfly or E.T. Cluster) in Cassiopeia Chart 2 or 7 The Owl Cluster is noteworthy on account of the fact it resembles an owl with outstretched wings. Look for the bright eyes in the finder scope. They re very close together, one is brighter than the other. The other stars aren t visible in the finder. The Owl Cluster fits snuggly in the FOV with the 26mm. For public viewing, it s just as well to use the 35mm as it will stay in view longer. For an extra challenge, see if you can find the fainter open cluster just a little distance away from his foot NGC 436, they make a nice pairing in the eyepiece. M38 and NGC 1907 in Auriga Chart 3 M38 is just visible in the finder. The stars are right on the cusp of being individually resolved. Make sure you ve not got it mixed up with M36 (its less impressive neighbour.) There s a modest number of stars of slightly varying brightness. The commendable thing about this star cluster is that a fainter cluster, NGC 1907, can be seen in the same FOV with the 35mm eyepiece. (You should be able to see NGC 1907 with a 10 inch scope in average light pollution.) 6

7 M37 in Auriga Chart 3 M37 is visible in the finder as a faint smudge. It s a snug/good fit at 80x. A large number of rather dim stars are visible, which are all the same brightness. It s definitely worth a look on account of the large number of stars. The stars in the centre of the cluster are arranged in lines that look like snakes. The one in the middle looks like the Greek letter Omega, with an extra bit on each side. Then again, maybe it s an octopus. M35 and NGC 2158 in Gemini, in-between Auriga and Orion Chart 9 M35 is just visible in the finder as very dim individual stars. There s a few bright stars and lots of dimmer ones. If you use the 35mm eyepiece, both M35 and a smaller open cluster, NGC 2157, are visible in the same FOV. NGC 2158 is very faint, more so than NGC 1907 mentioned previously. If it s not immediately apparent, look for a bow shape in the bottom left corner of M35. It s bent so it looks like someone s standing on the left hand side. There s a bright star at the bottom of the bow. Draw an imaginary line from this to the other tip of the bow, then carry on about four and a half times this distance. NGC 2158 is just slightly to the right. M35 is perhaps the second most impressive winter star cluster (after the Perseus Double Star Cluster) whilst NGC 2158 is interesting because it s a challenge to see. Double Stars Astronomical objects that are faint and fuzzy are usually considered to be deep sky objects. So strictly speaking, double stars aren t deep sky objects at all. But it makes sense to include them in the same guide as they come round on a yearly basis too. When it comes to doubles, the greater the colour difference between the two stars, the better. Slightly defocussing your scope may make the colours more obvious, in-focus (moving the eyepiece closer to the secondary mirror) works best. Brighter stars are also considered better because they stand out from the surrounding stars. Another factor is the separation. Some astronomers prefer close doubles because they like to test their scopes to see if they can distinguish, or separate the stars from one another. But for the purpose of showcasing the night sky to the general public, easily separated doubles are best. 7

8 Most double stars are true binary stars, rather than optical doubles. That is, stars that are bound together by gravity and orbiting one another, rather than chance alignments of stars as seen from Earth, which may be very distant from each other. Double stars can be quite difficult to locate in star atlases. Many doubles take their name from the Greek letter that marks their location. For example, Eta Cassiopeia is designated by the letter Eta in the constellation Cassiopeia. So you could look up Eta on Wikipedia and then find it on the atlas. I ve tried to describe the location of double stars as best I can. A black dot with a line through is the symbol for doubles in star atlases. Almaak in Andromeda Chart 2 (The star that marks the end of one of the horse s legs) Iota Cancri in Cancer, just to the right of Leo Chart 4 (Just above Praesepe) Eta Cassiopeia in Cassiopeia Chart 2 (Located in-between the third and fourth star in Cassiopeia, as you would write the letter W) Almaak is the best double star in the winter. The brightest star is yellow and the other white. It may become difficult to see later on in the winter, in which case switch to Iota Cancri. This double is similar but a little fainter. Another double that s worth a look at is Eta Cassiopeia. This is the other way around, with the brighter star being white and the much fainter star yellow. All three doubles are visible to the naked eye, and appear as one star in the finder scope. Use the 13mm eyepiece. April Begin observing at 8.30 at the start of April, 9.00 in the middle and 9.30 at the end. It will get truly dark about half an hour afterwards. April is the month for galaxies, so observations are best made on moonless nights. Open Star Clusters M35 in Gemini, in-between Auriga and Orion Chart 9 (See the winter section for a full description) Even in early April, M35 is still the best open star cluster to see. (M67 isn t that impressive, and M44 Praesepe is more of a binocular object it s too big to all fit in the FOV of a large telescope.) You re 8

9 unlikely to see M35 s companion, NGC 2158, however. By now it will be too close to the horizon. M44 Praesepe (The Beehive Cluster) in Cancer Chart 4 As the month progresses, M35 will slip lower and lower, and Praesepe will replace it as the best open cluster on show. It won t all fit in the FOV, but what is visible is impressive. The stars are very bright. Look out for the two triangles. Globular Star Clusters M3 Globular Star Cluster in Hercules Chart 6 M3 is the second most impressive globular star cluster visible in the northern hemisphere, and certainly the best one in April. M3 should be visible in the finder scope. It looks pretty good at around 150x in a wide angle eyepiece. Galaxies M81 (Bodes Galaxy) and M82 in Ursa Major Chart 4 In my estimation, these are the best galaxies to see in April, and possibly the best to see full stop. You re not going to see any detail in galaxies unless you re observing in a very dark location, but at least these two galaxies are relatively bright and they illustrate the shape of galaxies. They re both visible in the same FOV with the 35mm eyepiece. M81 appears round because it s flat on, and M82 appears cigar shaped because it s edge on. They can thus be used to explain that many galaxies are disc shaped. (See if you can see two dark lanes resembling a V that dissect the centre of the cigar.) Point your scope in roughly the right place using your Telrad, relative to the nearby constellation of Ursa Major. Now sweep the sky whilst looking through the finder scope. You ll definitely need a star atlas for this next bit. What you re looking for is a distinctive narrow triangle formed by three stars. There are another two bright stars to the side of this, parallel to the two stars on the edge of the triangle. The two stars are some distance away from the triangle and don t all fit into the same FOV, so you ll need to move your scope away from the triangle to locate them. M81 and 82, although not visible in the finder scope, form a boomerang shape with the two stars. Point your scope where you anticipate the end of the boomerang to be. The two galaxies should now be in the FOV on the main scope. If not, try scanning the immediate area looking through the 35mm eyepiece. 9

10 M51 (The Whirlpool Galaxy) and NGC 5195 in Ursa Major Chart 4 These two galaxies are visible together with the 13mm eyepiece. They re best found with a Telrad. The reason M51 makes it onto the list is because you probably stand more chance of seeing the spiral arms of this galaxy than those of any other. They re on the cusp of being visible in moderately light polluted areas. With reasonable conditions and a little magnification, the faint Bridge that joins the two can be seen. M101 The Pinwheel Galaxy in Ursa Major Chart 4 or 5 M101 is a popular target for sketching at dark sky sites, partly because it s face on thus displaying its spiral arms. It s not so great where I am. As far as I can see, there is no bright centre in this galaxy. It s just a very faint lighter area that is only visible when you tap the scope. This is one for a trip to the Negev Desert. Use the 35mm eyepiece. The Virgo Galaxy Cluster (M84, M86, NGC 4338 & 4435) in Virgo Chart 10 Picture an imaginary line in-between Arcturus (the bright star in Bootes,) and the star on the tail of Leo. From the half way mark, come down slightly until you get to another star. The galaxy cluster is midway between this star and the star in the tail of Leo. Use the Telrad, they re not visible in the finder scope. It s possible to see four galaxies in the FOV with the 35mm eyepiece: One in the top left, one in the middle, then carrying on in the same line, two fainter ones side by side near the field stop. The four of them form an extremely narrow Y shape. This is as close to one of those Hubble Space Telescope images of multiple galaxies that you re going to get. Maybe this is for the connoisseurs. There are actually loads more galaxies in this FOV. If you could pull a cord and switch off every light in a 50 mile radius you d be able to see them. The Leo Galaxy Trio (M65, M66 & NGC 3528) in Leo Chart 10 To locate the Leo Galaxy Trio, start at the bright star in Leo, and move down and to the left at about a 45 degree angle until the star is just outside the last Telrad ring. Three galaxies are visible in the FOV with the 35mm eyepiece. The brightest two are elongated and both at the same 45 degree angle to an imaginary line running between them. The third one is very faint and on the same side as the nearby bright star visible in the eyepiece. 10

11 Nebulae M97 The Owl Nebula in Ursa Major Chart 4 Unless you re observing from a very dark site, or have very good night vision, you probably won t see this without a UHC or OIII filter. Position your scope so that the third Telrad ring is on the nearby bright star which forms the bottom of the pitcher in Ursa Major. Magnification isn t crucial, but I favour medium power. The nebula is round that s about it. This isn t an object for making a big impression with beginners. It s probably an object to show people who are already into astronomy, but have never seen it because they don t have a light pollution filter. There is a certain amount of satisfaction in being able to say you ve seen it if it s eluded you for some time. It s also the best nebula observable in April, and therefore worth showing beginners just so they can say they ve seen a nebula. In dark skies it s a different story. The eyes, from where the nebula gets its name, are visible even without a filter. Double Stars Iota Cancri in Cancer, just to the right of Leo Chart 4 (Just above Praesepe) Iota Cancri is the best double star in April. The brightest star is yellow and the other brilliant white. It looks like one star in the finder. I use the 13mm eyepiece. May Observing can begin from 9.30 to as the month progresses, but it won t be truly dark for maybe three quarters of an hour after this. May is a noteworthy month because it s possible to see four of the brightest globular clusters all at the same time. Globular star clusters Globular clusters, as the name suggests, are roughly spherical in shape, as opposed to open clusters which are irregular. They also have many more stars, typically hundreds of thousands. I use the 13mm wide angle eyepiece that gives me around 150x magnification. They re all visible in a 9x50 finder scope, M13 easily, the others, only just. M13 in Hercules Chart 6 M13 is the brightest globular star cluster in the northern hemisphere. It has lines of stars emanating from the core that curve round slightly in one direction, so it looks like some kind of jellyfish 11

12 swimming through water. The core is a fuzzy smudge of light with some individual stars visible. There s a darker region in the edge of the core that some people say looks like a propeller (or Mercedes car logo). It s on the side with least stars in the outer region. To my eye, there are lots of darker regions, and I wouldn t say I d have notice the propeller unless someone said it was there. For an extra challenge, try for NGC 6207, the magnitude 11.6 spiral galaxy just a short distance away from M13. In a low power eyepiece it can be seen as a very faint diagonal slash sitting alongside M13, the two make a splendid slight. The constellations around M13 don t stand out as much as the others, so try finding it using the brightest two stars in that area of the sky. The first is Vega, in Lyra, and the second is Arcturus in Bootes. It should then be possible to find the box of four stars in the middle of Hercules. But which side of the box is it on? This is the question I ve found myself asking due to the fact the box rotates over the course of the spring and summer. The box has one side that s shorter than the others. Imagine the box is a mug, and the shortest side is the base. M13 is just about where the top of the handle would join the mug, on the right hand side, about a third of the way down from the top right star to the bottom right star. Remember to call these four stars the keystone on club night, not the teacup! M92 in Hercules Chart 6 M3 in Canes Venatica, just above Bootes Chart 5 (See April) M5 in Serpens Caput, below Bootes Chart 11 M92 has a more concentrated core. M3 has lots of stars, all of a similar brightness. M5 is the smallest of the four, or at least it looks that way; it s lower down so the brighter sky obscures the outer portion. It has a more defined edge to the core. On two sides it almost looks like a box. M5 never gets as high as the others and is therefore more difficult to see, but it s at its highest during May evenings. Find it using the line of four bright stars to the left, which look like a bolt of lightening. Galaxies and Nebulae M81 (Bodes Galaxy) and M82 in Ursa Major Chart 4 M51 (The Whirlpool Galaxy) and NGC 5195 in Ursa Major Chart 4 M97 The Owl Nebula in Ursa Major Chart 4 (See April for the above three objects) The best galaxies to see are M81 and M82, followed by M51 and NGC The best nebula is still the Owl Nebula. 12

13 Double Stars Iota Cancri in Cancer, just to the right of Leo Chart 4 (Just above Praesepe) Cor Caroli and Struve 1688 Chart 5 (Just below M94) in Canes Venatica, below Ursa Major Iota Cancri is the best double star for as long as it s observable. The brightest star is yellow and the other brilliant white. Later on in the month, switch to Cor Caroli. There s not so much colour difference in this double, but it still looks nice. The brighter star is brilliant white and the fainter one is off white. Both doubles are best viewed through the 13mm eyepiece. Alternatively, use the 35mm on Cor Caroli. There s another double star close by, Struve 1688, which sits nicely in the same FOV. Even at this low magnification, they re both still obviously doubles. Struve is quite faint. Both its stars are the same brightness and off white. They re also slightly wider. June and July Observations at this time of the year are difficult because it doesn t get dark until late. But if you re that keen, the objects listed in the next section are also visible in the small hours in June and July. If you re going on holiday to somewhere really remote (hence the suggestion of a small scope earlier!) why not have a go at seeing the Milky Way? If the sky is dark enough, you should be able to detect a slightly lighter band running overhead that corresponds to the band shown on star charts. Don t forget to pack your planisphere and red torch! August to October At this time of year the night sky contains possibly the largest variety of objects; you ll be like a kid in one of those old fashioned sweet shops. There are so many stars in the summer leg of the Milky Way that just sweeping the sky with a wide angle eyepiece is a spectacle in itself. Late summer to early autumn is also the only time of year when it gets dark reasonably early and is still quite warm. All this makes August through to October a good time to show guests and friends the wonders of the night sky. 13

14 Month Start observing Fully dark First half of August 10.15pm 11.00pm Last half of August 9.30pm 10.15pm First half of Sep 8.30pm 9.15pm Last half of Sep 8.00pm 8.45pm First half of Oct 7.30pm 8.15pm Last half of Oct 7.00pm 7.45pm British Summer Time ends Very end of October 6.00pm 6.45pm Globular Clusters M13 in Hercules Chart 6 (See May) M92 in Hercules Chart 6 (See May) M15 in Pegasus Chart 13 M2 in Aquila, just below Pegasus Chart 13 August is a good time to observe M13, it really does look special while it s still high in the sky. I d say this should be the highlight of an event. If it disappears behind a chimney in October, try M92 or M15. M15 is smaller than M13, but quite bright with a concentrated core. M2 is harder to resolve into individual stars. All four are visible in the finder and look best in the 13mm eyepiece. In order of impressiveness, the top four globular clusters are M13, M3, M92, and M15. With these, you should be able to show people a good example of a globular cluster from April to December. Nebulae The Eastern Veil Nebula NGC 6992 and 6995 in Cygnus Chart 7 The Eastern Veil Nebula is a gem of the summer sky. It is quite faint, so you ll have to be extra careful to follow the tips on observing, listed previously. The centre of Cygnus comprises of five stars that form a cross. The Eastern Veil Nebula is just off the star that marks the left hand tip. (It s usually pointing slightly downwards at this time of year.) Move in a 7 O clock direction from this star (with 12 O clock pointing back to the centre star in Cygnus.) Position the imaginary fourth Telrad ring on the star that marks the left hand tip of the cross. You may have difficulty seeing this in the finder scope and in the main scope without a filter. A UHC or OIII filter makes all the difference - the OIII is best. You ll probably have to sweep the sky a bit while looking through the main scope. The nebula is a long arc that fills the entire FOV in the 35mm eyepiece. It s shaped that way 14

15 because it s the remnants of a star that exploded. Some detail can be seen in the ark, particularly at the top right end where it s noticeably more irregular. Although it s not bright, it is a very interesting shape, even beautiful I would say. The arc is said to resemble the side profile of a face or bride in her veil, hence the name. M27 The Dumbbell Nebula in Vulpecula, just below Cygnus Chart 6 The Dumbbell Nebula is brighter and therefore a better target in some respects. The dumbbell (or apple core) shape is visible without a filter. A UHC or OIII filter darkens the sky and makes it stand out more. I marginally prefer the OIII filter. This reveals nebulosity on either side, so the nebula looks oval, with a brighter middle portion forming the dumbbell across its width. Magnification doesn t seem to be crucial, so I opt for medium power and use the 26mm eyepiece. You should be able to see M27 in the finder scope. Position the imaginary fourth Telrad ring on the nearby bright star, and you ll be about in the right place. M57 The Ring Nebula in Lyra Chart 6 The Ring Nebula is visible in the finder, and appears as an oval ring through the scope. It s visible without a filter, but a little better with a UHC. As M57 is small, use high magnification, the 13mm LVW is fine. There s some debate as to whether this is actually the same shape as the Dumbbell Nebula. Maybe exploding stars produce the same shape nebula, but look different depending on the angle they re viewed from. The Blue Snowball NGC 7662 in Lacerta, above Andromeda Chart 2 Small, round and pale blue. One can see how planetary nebulae got their name - because of their strong resemblance to a planet. It looks best in the 13mm eyepiece with no filter and is visible in the finder scope. The Western Veil Nebula NGC 6960 (aka The Witch s Broom) in Cygnus chart 7 This would fill the entire FOV in the 35mm eyepiece if I could see the whole thing. All I can see from my back garden is the brighter, narrower end (the handle part of the broom,) which snakes down from the bright star 52 Cyg. The fainter end, on the other side of the star, is only visible out in the countryside. You ll need a UHC or OIII filter to see this nebula take your pick which one. Start from the 15

16 same star you used to find the Eastern Veil, on the wing of Cygnus, only this time come down in a 4.30 direction. Point your scope so the star would fall on the imaginary fourth Telrad ring. It s not visible in the finder, scan the sky through the main scope using a light pollution filter. Double Stars Most astronomers are more into nebulae than double stars, including myself until recently. To my horror, I discovered one evening that newcomers were more impressed with Albireo than with the Dumbbell Nebula! Never underestimate the beauty of double stars. Albireo in Cygnus Chart 6 (The star that marks the head of Cygnus the Swan, in-between the Dumbbell and Ring Nebula) Albireo is arguably the most impressive double star. The two stars are separated by a good distance. The brighter star is yellow, and the other is brilliant white (or sapphire blue to some people s eye.) I prefer the view through the 13mm LVW. The Double Double in Lyra Chart 6 (Just to the left of Vega) The Double Double is best viewed through the 8mm Radian. At this magnification, they all still fit in the FOV, and the doubles can just be separated. The appearance is of two stars extremely close to each other, then a wide gap, then another two stars extremely close to each other. At lower magnifications they just look like two slightly large stars. All four are white. Omicron 1 Cygni in Cygnus Chart 6 Technically classed as a double star, Omicron 1 is actually a triple star system. The centre part of Cygnus consists of five bright stars that form a cross. Point your scope halfway along a line between the star that marks the top of the cross and the star that marks the right hand tip. Now move your scope slightly away from the star in the middle of Cygnus so that the line now resembles the angle of a coat hanger. There are two stars just visible to the naked eye. Omicron 1 is the star closest to the centre of the constellation. All three stars are visible in the finder scope. They look good in the 35mm eyepiece, where they span about an eighth of the FOV. The central star is the brightest and is obviously yellow, the other two are brilliant white. The faintest is only just brighter than the background stars, and is perhaps the bluest. 16

17 Galaxies M31 The Andromeda Galaxy in Andromeda Chart 2 M31 is the biggest and brightest galaxy in the night sky, and can even be seen with the naked eye on occasions. You ll find it easily in the finder scope. Through a telescope, its bright core can be seen, plus the much fainter outer regions. The brightest of M31 s satellite galaxies, M32, is also visible in the same FOV in the 35mm eyepiece. The other satellite galaxy, M110, is only really noticeable a few miles out into the countryside. M110 is on the opposite side of the Andromeda galaxy to M32, and twice as far away. Using the length of Andromeda s disc as a horizontal line, M110 would be directly above Andromeda s core. (If the core of Andromeda was the centre of a clock face, M110 would be at 12 O clock and M32 would be at half past four.) It s not possible to observe all three galaxies together as the two outer ones are virtually on the field stop. To my great disappointment, I ve been unable to see the dust lanes; that will have to wait until a holiday sometime. They re located in the outer region of M31, on the same side as M110. Open Star Clusters The Perseus Double Star Cluster NGC 884 and 869 in Perseus, towards Cassiopeia Chart 2 (See the Winter section) By August, the Perseus Double Star Cluster is visible again in the north east. It s an eye popper even when it s close to the horizon. M11 The Wild Duck Cluster in Scutum, towards the bottom of the Milk Way Chart 12 There are lots of clusters in this immediate area, which could make it a little difficult to know if you ve got the right one. However, M11 is the only one that s visible in the finder scope. I recon this is the best open star cluster in the summer leg of the Milky Way, and a good one to show people, especially if there s a tree in front of the Perseus Double Cluster. M11 would be even better if it were higher in the sky and out of the worst light pollution. Unfortunately it never gets very high. There are lots of faint stars, and a few brighter ones. It looks a bit like M37 in the winter. Although it fits into the FOV in the 26mm, I prefer the view in the 35mm eyepiece. There s definitely a pattern there. It reminds me of the ripples you get in sand after water has been flowing over it. Couldn t see the Duck. It supposedly resembles the flying V shape that ducks/geese make when flying. 17

18 The Coat Hanger Asterism Cr399 in Vulpecula, just in front of Cygnus the Swan s head Chart 6 This group of stars really does look like a coat hanger, even if it is upside down your view may be different! Perhaps the novelty value would appeal slightly more to children. It s best observed in the finder scope, where it spans just under half the FOV. The Coat Hanger is an asterism, rather than a cluster. In other words, the stars aren t near each other or gravitationally bound in space because they re different distances from earth. The curious pattern just happens to be a chance alignment as seen from our location. November and December From this time on it gets darker much earlier so you can observe throughout the week, rather than waiting for the weekend when you don t have to go to work the next day. If you re planning any star parties, they re best held sooner rather than later before everyone is too busy getting ready for Christmas. Views of globular clusters and nebulae get more difficult week by week at this time of year. This is another good reason to hold any events in November, rather than December. For the same reason, it s preferable to observe as soon as it gets dark when these faint objects are still relatively high in the sky. Observations are best made on moonless nights. Observing can start as early as 5.30pm in early November, and 5.00 O clock for the remainder of the year. It gets fully dark 30 to 45 minutes afterwards. Star parties for the general public however, should avoid mealtimes. Galaxies M31 The Andromeda Galaxy in Andromeda Chart 2 (See August to October) M31 is at its highest point in the sky right now, so this is one of the best views of a galaxy you re going to get all year. Look out for M110 and those pesky dust lanes. M33 The Triangulum Galaxy in Triangulum, just below the Andromeda Galaxy Chart 2 M33 is supposedly the galaxy that shows most detail when observed under a really dark sky, and it s certainly a popular target for sketching. Where I live it s just a very faint patch of nebulosity, which is a lot more noticeable if you move the scope. It s only just visible, and can t be seen at all in the finder. This is another one to 18

19 remember for the camping trip. During late autumn it s highest in the sky, so now s your best chance of seeing it. Use the 35mm eyepiece. Open Star Clusters The Perseus Double Star Cluster NGC 884 and 869 in Perseus, towards Cassiopeia Chart 2 The Owl Cluster NGC 457 in Cassiopeia Chart 2 or 7 M37 in Auriga Chart 3 M38 and NGC 1907 in Auriga Chart 3 (See the winter section for all of the above) The Perseus Double Star Cluster and the Owl Cluster are now high in the sky and at their finest. M37, M38 and NGC 1907 are quite low down but get progressively easier to see later into the evening and towards the end of the year. Globular Star Clusters M13 M15 in Hercules Chart 6 (See May) in Pegasus Chart 13 (See August to October) M13 is still the most impressive globular cluster if you re observing soon after it gets dark in early November. Thereafter, M15 will see you through to the end of the year. Nebulae The Eastern Veil Nebula NGC 6992 and 6995 in Cygnus Chart 7 M27 The Dumbbell Nebula in Vulpecula, just below Cygnus Chart 6 The Blue Snowball NGC 7662 in Lacerta, above Andromeda Chart 2 (See August to October for the above three) M76 The Little Dumbbell in Cassiopeia Chart 2 or 7 M42 The Orion Nebula in Orion Chart 9 (See January to March for the above two) The Eastern Veil and Dumbbell Nebula are still visible depending on what time you re observing. But they re past their best as they edge further and further towards the light pollution in the lower region of the sky. The problem is that there are no impressive nebulae to replace them afterwards. It s therefore as well to observe them for as long as possible. Going into December, the Blue Snowball and Little Dumbbell are high in the sky. They may not be 19

20 visually stunning, but they do have nice names, and the Blue Snowball is genuinely blue rather than brilliant white. (Well perhaps not neon blue.) If you really want to show people a fantastic nebula in December, here s a little trick. Assuming you have a clear horizon to the east, observe late in the evening and the Orion Nebula will be visible. (After 9.30 in early December, and 8.30 in late December.) Double Stars Albireo in Cygnus Chart 6 (The star that marks the head of Cygnus the Swan, in-between the Dumbbell and Ring Nebula) Almaak in Andromeda Chart 2 (The star that marks the end of one of the horse s legs) Eta Cassiopeia in Cassiopeia Chart 2 (Located in-between the third and fourth star in Cassiopeia, as you would write the letter W) Omicron 1 Cygni in Cygnus Chart 6 (See August to October) Albireo is still the best double star for a while, after which, substitute it for Almaak in late Autumn. This is similar but a little closer together. Also take a look at Eta Cassiopeia, which is well placed for the whole two months. This double is the other way around with the larger star being brilliant white. All three are best viewed through the 13mm eyepiece. Omicron 1 Cygni is still visible low down in the sky. Astronomers routinely exaggerate the depth of colours of double stars. Orange is more like yellow, and blue is actually brilliant white. (Remember to take into consideration that some eyepieces are warmer than others.) What s hard to exaggerate, however, is the subtle quality of the light. For example, the word yellow just doesn t do justice to the main star in Almaak. It looks like the reflection off a golden mirror. It s very striking against the purity if its brilliant white companion. Summary I brought my current scope so that I would be able to show folks some good views of astronomical objects at any time of the year, without having to wait until Jupiter was around. The interest has been modest, but I ve entertained a few people over the last twelve months, so it s mission accomplished. 20

21 I ve also learnt a lot myself. If you ve read the whole of this guide, it should be obvious that the various different kinds of deep sky objects are not distributed evenly across the sky. Different months are better for different kinds of objects. Our galaxy is a disc shape with spiral arms, and we re about three quarters of the way out from the centre, towards the edge of the disc. The galaxy s core lies beyond the stars of Sagittarius. The lighter band across the sky is the disc edge on. Open star clusters and nebulae are within the disc of our galaxy, which is why they re found mainly in certain regions of the sky. Globular clusters, on the other hand, are distributed throughout a spherical area encompassing the disc. Contrary to what one might assume, galaxies are not distributed evenly throughout the universe, but are linked together by gravity in a network of lines called cosmic strings. Just to give you an idea of the scale of things; the earth is just under 8000 miles in diameter, but if it were the size of a pea and the sun was a metre across, the distance from the sun to the nearest other star would be almost 17 thousand miles! Everyone loves the moon and the planets, but deep sky objects are fascinating because they give us an insight into the true structure and size of the universe. They re also some of the most beautiful objects in nature. David Geary charnwoodcottage@btinternet.com February 2016 If you know of a deep sky object or double star that s better than the ones I ll listed at a particular point in the year, please let me know. In memory of my two lovely cats, Jess and Meg, who always enjoyed the opportunity to stay outside a little longer while I was busy looking at the stars. 21