The Official. Online Astronomy Society. Guide to. Beginning. Astronomy. Alastair Leith

Transcription

1 The Official Online Astronomy Society Guide to Beginning Astronomy By Alastair Leith

2 Contents Online Astronomy Society... 3 Beginners Guide... 3 Starting Astronomy... 3 So you want to take up astronomy do you?... 3 Binoculars... 3 What will binoculars show?... 4 Learning the constellations... 4 A refracting telescope... 7 Reflecting telescope... 7 Mounts... 9 Suggested Projects Observe Moon Solar Project work Charting planetary movement Taking pictures of the stars Maintenance of Kit Conclusion Further Reading Sky Charts January Sky February sky March Sky April Sky May Sky June Sky July Sky August Sky September Sky October Sky November Sky December Sky... 30

3 Online Astronomy Society Beginners Guide Starting Astronomy There are many reviews on beginning astronomy, good books for beginners out there, but I thought it was time the Online Astronomy Society had its own booklet on starting out Astronomy has never been more popular as a science than it is now. With advocates to the science being made more prominent with the likes of the BBC Stargazing Live, astronomy has never been more accessible or affordable a subject to follow, with more ordinary people than ever performing work of scientific value. I have wanted for some time to write a guide for beginners which is practical, based on experience and brings the pathway forward to the 21 st Century. Sir Patrick Moore has long advised people to start with the naked eye and binoculars and learn the sky. Though I don t necessarily agree with his advice on telescopes, that anything below 3inches for a refractor or 6inches for a reflector is not much use for serious work. Define what serious work is? Serious work is not the issue for the beginner either, enjoyment and learning is. So let s begin. So you want to take up astronomy do you? Well first off, let s not go rushing off to buy the latest and biggest telescope on the market. That s like buying a car before you can drive. Simply take time out, buy or borrow a cheap pair of binoculars and get to know the sky. Starting first with the naked eye, get your bearings. Appreciate the layout of the sky and the constellations. I recommend a reasonable pocket sized handbook for this, red torch and a pair of binoculars. Binoculars Ideal magnification for binoculars should be 7x50 or 10x50 Binoculars should be light and easy to hold. Anything over 10x50 they will be too heavy for long periods of use. What do we mean by 10x50 though?

4 The 10 is the magnification of the binoculars, the 50 is the diameter of the binocular objectives (the larger lenses you see). So a pair of 10x50 s will be 10x magnification, and 50mm diameter. Which might not sound a lot but it s ideal for getting to know the sky and learning the stars. Binoculars nowadays are often very cheap, anything from 10 upwards will buy you a decent pair. Plus if your interest is short lived they can be used for other purposes. What will binoculars show? The obvious things are craters of the Moon, however you will also see Jupiter and its Moons Andromeda Galaxy M33 another galaxy, face on. (Excellent conditions needed!) M13 a globular cluster in Hercules. (Reasonable conditions needed) M42 the Orion nebula. Learning the constellations Generally the easiest constellations which many won t fail to recognise are: Ursa Major, the great bear, this is visible ALL year round from Northern Latitudes and is key for identifying the pole star Ursa Major is also known as the Big Dipper, or the frying pan for obvious reasons. You can see it highlighted above. This constellation in itself has many interesting objects which you can come back and view later. However here is what I suggest. Familiarise yourself with the constellation, get to recognise it, it may very well be that due to light pollution that it s the only one you can see clearly. While getting familiar with the constellation why not take time out and learn the star names. Learning star names will not only help you better appreciate the constellations but it s great at parties when you can name stars people pointed to!

5 Once you have learned the constellation, and the names of the main stars in it, it is now time to investigate what is of interest within. Many of the objects listed below are visible only through a small to medium sized telescope. We will discuss telescopes later in this guide. You can also see from this chart that The Plough extends much further to the remainder of the Big Bear. And meets other constellations where you can begin to learn. One thing I did as a kid was I stood out there with a pencil drawing dots of other stars around the constellation I had learned. Using a star atlas I referenced these and used this as a means of identifying another constellation and repeating the process. Often the best time to be doing this is in the winter/ autumn time when the skies are darker and clearer, it is also when one of the most celebrated constellations is in the night sky, Orion.

6 Orion is impossible to miss even as a complete beginner, I know as its one of the first I recognised. I often call it the Bow Tie! for obvious reasons. Not only easily recognisable but contains some interesting objects. Betelgeuse for example is a red giant we expect to die at any time. The star is the only one other than our own Sun which can be resolved as a disc. (by professional telescopes). It would also swallow up most of our solar system. As the sun will do when it dies M42 is the Orion nebula which can even be see with the naked eye! A fantastic binocular object that is easily seen. The purpose of this guide is not to reinvent the wheel in terms of astronomy guides however the above pointers should help you to get going

7 Once you have learned many of the constellations, and you re still keen to keep going, it is worth investing in a small telescope. A refractor is likely to give you less issue with mirrors or collimation; however the pros and cons of both will be discussed. Firstly, what is the difference? A refracting telescope So a refracting telescope is a long tube containing a large objective lens and an eyepiece Reflecting telescope

8 There is more than one type of reflecting telescope but the most common beginner s telescope; the Newtonian will be discussed here. Light collects in the bottom of the tube, and is reflected to the secondary mirror then to the eyepiece. These telescopes are usually intrinsically larger than refractors and are generally better suited to deep sky observing than refractors which by and large are better suited to planetary, lunar, and solar work (NEVER LOOK DIRECTLY AT THE SUN WITH ANY TELESCOPE, IT WILL BLIND YOU!). Which to get? Both have their pros and cons, my personal favourite are to start with a refractor. Main reason being is though it has a low aperture; it suffers fewer of the problems a reflector can have like collimation issues (see later) and dirty mirrors. However beyond the planets and the Moon it has more limited ability with deep sky objects (this does NOT mean you can t see any, just means more limited). Reflectors, although they have the potential of allowing you to view more due to having a greater light gathering capability (larger mirror in other words), they do suffer problems with mirror alignment and with mirrors needing to be re silvered after a while. The former issue with the correct guidance from a local astronomy society will be quickly eradicated. Pit holes to avoid. High street shops are often the worse place to get a telescope from, especially refractors. They will often sell small low grade telescopes in fancy packing promising the earth in magnification. Higher magnification is NOT always the best thing. However there is another pitfall to look out for You will often see refracting telescopes with objectives stopped down with a plastic ring Stopping Ring Objective

9 The reason they do this is the central lens is better quality than the outer, so rather than cut it out, they make the telescope look bigger by covering the lesser part over with a ring, a dirtier trick is they will often place this ring inside, not outside the objective selling it with the larger diameter advertised. Mounts Generally it can be argued there are two types, a) Altazimuth b) Equatorial Both have their advantages and disadvantages. Altazimuth Mouth: Probably among the most common available on the market and a favourite with beginners. Here is a typical one fitted with a star diagonal and a finder. A star diagonal is useful for not having to squat at the eyepiece. The mount just moves left right, up and down both motions need to be manually adjusted by the observer. This is a point and look setup, not really suitable for taking photos. Equatorial mount is more complex. The weights are needed to balance the telescope. The movement is this time in line with the earth s rotation so the mount needs to be polar aligned. The telescope can only move in RA (East to west) or Declination (up and down), can be a bit fiddly for an absolute beginner. However, if setup correctly, motors can be added making it suitable for taking pictures.

10 Fork Mount Seen mainly with another kind of telescope we have not so much discussed here, the Schmitt Cassegrain Telescope. We will only briefly touch on it here. Similar to the author s setup, the telescope you can see sits on a tripod but is mounted in a wedge which is the same as the observers latitude. The idea is this tilts the telescope towards the direction of the pole star. It is closely related to an Altazimuth; however that former is not polar aligned. There are other factors to consider when buying a telescope, but usually before making the final decision, its best to venture to a local astronomy society to ask advice there, even try out different telescopes to see what is best. Don t forget, you re never stuck with what you buy, you can always upgrade to better later, this is the game we play in astronomy! Where too from here? It is definitely worth getting to meet other like-minded people. A local astronomy society often has a mixture of like-minded people who are able to advise you on how best to use your equipment and how to get to the next level. The Online Astronomy Society also caters for beginners to intermediate with members more than happy to help you develop. What happens once I have learned all the constellations and seen all I can with the equipment I have? It is likely then you will want to consider a specialism, and there are plenty you can get involved with, some giving you the opportunity to do some real science. This is not the place to be discussing other areas in depth but if you plug the below keywords into Google they will point you in the right direction

11 Variable/ Double Stars Lunar Observation Planetary Observation Solar Observation (never directly with a telescope though). Astrometry (not many people do this) Spectroscopy (or this) Interesting Projects to carry out Observing the Movement of Jupiter s Moons This can be done with ANY small telescope, see if you can plot Jupiter and its Moons over a period of a few nights; it s interesting to watch them move. Any astronomy magazine will assist you in naming them. Suggested Projects Observe Moon See if you can make detailed observations of the Moon. Even two half-moons will never have the same detail due to the way the Sunlight hits the moon. Solar Project work I have mentioned more than once and will do so again, NEVER OBSERVE THE SUN DIRECTLY WITH ANY TELESCOPE, YOU WILL BLIND YOURSELF. I make no apology for mentioning it again here either. However if you are able to, use a refracting telescope, NOT a reflecting telescope to project the Suns image onto a piece of paper. You will be able to see what we call a white light image of the Sun

12 Solar Sketch made using the above method by Mick Murphy, Ireland. This chap learnt for Online AS how to do solar projections. From this it is possible to identify Sunspots on the Sun. Sunspots are cooler areas of the Sun caused by magnetic fields. This picture is courtesy of Richard Bailey. An interesting project could be to plot the movement of the sunspots across the Suns disc over a period of a few days. Please keep in mind two things if you re going to do this. a) NEVER point the telescope at the Sun for too long, you will damage it. b) NEVER use a solar filter for the EP even if it came with the telescope. Charting planetary movement Try observing, sketching or imaging surface details of Jupiter or Mars over a few hours when either are up each night. You will notice that due to the rapid rotation of these heavenly bodies the surface detail changes quite often, enough to notice if you took a picture or made a sketch every 45 minutes or so! Taking pictures of the stars We have tutorials on the DVD about doing this, but it s definitely worth mentioning this here. This is also the first thing which attracts beginners to astronomy. I admit that although I too have been bitten by the bug, it always in my opinion adds to the value if you know what your images are and the purpose to it rather than just taking pretty pictures. I should

13 also mention that the beginner might want to know why to bother taking pictures of the Moon or the Orion nebula. My answer is well when you go on holiday, why bother taking pictures of famous landmarks when others have already done so. The answer is because they are YOUR pictures, and this is where the added value comes in. As much as I have resisted imaging as a hobby as I do not class it as amateur astronomy per say (its more astrophotography), some interesting science can still be carried out. So I am going to say a few words here on this in terms of kit to you. First off, there is no need to blow the household budget, with a little time and patience you can take half decent shots of the Moon and the planets, and there are number of articles on this. Serious astrophotographers will use expensive DSLR s and cameras, you don t have to. For starters, some webcams can be used to take very decent pictures of the Moon and the planets. The Toucam Pro 2+ webcam is widely used by amateur astronomers to picture the Moon and Planets The trick is to unscrew the lens and screw in a 1.25 inch nose adapter

14 Here is one with a filter fitted on the end This then fits down the eyepiece barrel enabling you to capture images with it. Please see the tutorials mentioned on the DVD if you re unsure how to do this. Webcams are particularly useful for Imaging the Moon Venus, Mars, Jupiter, Saturn, and the Moon. You MIGHT get some of the Orion Nebula with it, however beyond that you will need to use a DSLR cameras as described in the tutorials on this DVD. The author uses a Canon DSLR 1000D camera, which is inexpensive, compared to other models and can have what we call a t-ring and adapter added to make it suitable for astronomy You can see the authors setup here complete with the t adapter and the screen in nose piece The lens will unattach from the body (consult manual if unsure how to do this)

15 Exercise caution here in that you don t want any dust of debris falling into the camera as you do this. The cameras now complete with the adapter fitted. Note the lens cap is kept on. This is to prevent any dust or flies from wandering in until you re ready to use it. A few hints if doing this Ensure that whatever you affix to the adapter, including the cap, the nosepiece, even filters or Barlow s are clean and dust free before fitting it either to your camera or the telescope. You don t want dust particles or such like messing up the sensor of the camera or falling down the tube of your telescope. A little OCD of me but these are things I try to avoid. Puritans would suggest resting the camera as below until needed. Small measures like this can keep dust and other mites from appearing on the images you take!

16 Once ready, the camera is ready to put into the rear end of the telescope, where you normally put the eyepiece. Ensure before you proceed that the camera is NOT too heavy for your mount. The reason too why this model is popular is due to the live view of the camera, for many it s a lifeline for those who work without a laptop Live view of the camera (the big screen can be really useful in astronomy) There is much more left to cover regarding the use of the DSLR for astrophotography, indeed it is an art form in itself. However things to note with using the DSLR are it s only really ideal for imaging the Moon and deep sky objects. If it s the planets you desire, then I would suggest keeping with your toucam, so this is not and either or game. You will need both. Also things which have caught me out when using my camera are flat batteries, so ensure you have spares or that what you use is fully charged! Ensure too if you re working from Live View that the SD card has been inserted back in (see below) This is a view showing the authors 8 Gig SD card which the camera will store images on if not connected to laptop

17 The live view indicator is used to show the level of the battery The battery compartment at the rear. This may vary from model to model Maintenance of Kit The first temptation of any beginner is to keep the kit sparkling clean. The advice is DON T clean anything unless you REALLY need to. How to clean kit is a subject for elsewhere however for things like DSLR cameras it really is better to take it to a specialist for cleaning. Removing grit off eyepieces should be done using a blower to blow the grit off, followed by a camel brush to gently wipe off if that fails. The important thing is to keep your kit in a case where you can get to it easily and will keep your kit clean and dry when not in use. Conclusion I hope this mini guide has been of some use to the beginner, in writing it I have tried to keep it simple and to the point. However allowing for enough for the beginner to develop with this guide and move forward with their interest. In writing this I have tried to base it on mine and others experiences rather than any book. Nothing written above has been based on anything other than hard won knowledge. I would like to add that while astronomy is a very rewarding interest to follow it is not without its woes and challenges. Light Pollution is a constant which hampers most amateur astronomers at some point or other. In many cases we learn to adapt using filters and such like. Weather cannot of course be helped. Then of course there are conditions which effect the seeing of the sky when it s clear. Just because a sky may be blue with the potential of going clear it does not necessarily mean the seeing conditions are going to be great. You will notice the difference if you see fewer stars and more of an orange glow. If it is very humid

18 when you setup it is likely only going to be good for the Moon and Planets (with a lot of possible turbulence even then). Astronomy also has the potential of being extremely expensive if you are not careful, so shop around and know what you want and what you want to do with it. Star charts are going to be the next resource you will likely want from this guide; I have included them at the end. Also a reading list, these books are not recommended to look good and sit pretty on a bookshelf, they are texts which YOU will find invaluable on your journey to becoming an amateur astronomer Turn Left at Orion Further Reading Invaluable resource for knowing what is up there and how it will look through the telescope. One of the few resources which completely ignores the camera and looks at what you can SEE with the eye down the eyepiece Collins Gem Star Atlas, No amateur astronomer should be without this. An ace publication, I still use mine to this day, its over 20 years old now! For a general introduction to the stars and planets I recommend Wonders of the universe Professor Brian Cox Wonders of the Solar System Professor Brian Cox. Societies Free to join and also has a forum, offers a magazine, webinars and tutorials for paid members. 15 per year to join. Society Popular Astronomy British Astronomical Association HantsAstro Magazines Become a premium member of the Online Astronomy Society and receive our magazine, fully downloadable with all the information you will need for your nights viewing.

19 There is also the Sky at Night Magazine Astronomy Now Sky Charts Provided courtesy of Ninian Boyle of January Sky

20 February sky

21 March Sky

22 April Sky

23 May Sky

24 June Sky

25 July Sky

26 August Sky

27 September Sky

28 October Sky

29 November Sky

30 December Sky