Introduction to Astronomy

Before I begin this article let me first of all thank Austin Hastings and Tom Mulcahy of the Cork Astronomy Club for their help and enthusiasm in the past years in making this a most interesting hobby for me.

Let me mention the Solar System. This consists of the Sun, which contains 99% of the mass of the solar system, Mercury, Venus, The Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto the most distant at 40 Astronomical units from the Sun. (40 X 93,000,000) miles although due to the orbit of Pluto this is not always the case.

Now if you consider that the Earth fits 12 times across the diameter of Jupiter you can begin to see just how small our planet Earth really is

The Sun is 109 times the diameter of the Earth.

Betelgeuse, a vast red supergiant Star in the Constellation of Orion varies between 300 and 400 times the diameter of the Sun, if this Star replaced our Sun it would easily engulf the earth.

While reading my favourite Astronomy Magazine “Sky & Telescope” recently a comment by one of the writers, Richard Bray, caught my attention. If you were to hop on an aircraft and head towards the Sun travelling at 600 mph., it would take you 21 years and 26436 consecutive airline meals to get you there! Think about it, the Sun is approximately 93 million miles from us, (although it is closer in the wintertime). That counts as one Astronomical Unit. At these distances we forget about miles, as the figures are incomprehensible.

It takes about 8 minutes for light from our Sun to reach the earth. The nearest star, Alpha Centauri, is 271,400 times further from the Sun than we are and it takes light from that star 4.3 years to get to us travelling at a speed of 186000 miles/second.

The Sun is just one of about 100,000 million stars which make up our galaxy, the Milky Way.  Our nearest galaxy is Andromeda, now this is where things start to get interesting, this galaxy is easy to spot with binoculars as a white fuzzy patch in the night sky, but what we see is an image of it as it was 2.25 million years ago, not as it is right now, If you were observing the Milky Way from Andromeda it would be exactly the same, could you imagine the following, a message sent by radio would take 2.25 million years to get to a star in Andromeda and the reply would take the same amount of time to get back.

The Universe is made up of millions of Galaxies and I am sure life exists, (probably not as we know and understand it) on many planets. In the past few years approximately 50 planets have been discovered orbiting nearby stars less than 12 light years away, these stars are just in our back gardens in terms of distance, some of these planets have 3 times the mass of Jupiter, the largest planet in our solar system.

 

Jupiter and Saturn are incredible to view, they are both gas giants, Jupiter at about 400 million miles distance has 16 moons, 4 of which, Io, Ganymede, Europa and Callisto are easy to see, visible with just binoculars and a steady hand. Saturn has about 21, the largest Titan is also visible with binoculars.

The Earth takes 1 year to orbit the Sun, but Saturn takes 29.5 years to do so as it is nearly 10 times farther than the earth is from the Sun. Saturn is an amazing planet to observe and with a telescope and good eyepiece it is no problem to peer into deep space between the rings of Saturn and the planet itself.

 

 

When you are thinking about buying a pair of binoculars or a telescope let me say one or two things, a lot of telescopes in the shops are just toys and provide no useful purpose at all, except to waste your money. Statements like “600 times magnification” is, contrary to what you might think almost impossible to achieve even in expensive telescopes, seek advice from an active amateur astronomer or join a local club.

 A good pair of 7X50 to 10x50 binoculars will give much better results. In my opinion a good pair of binoculars is a vital astronomy tool and will cost about £100 at least.

Different types of telescopes are available and I will not dwell too much on these in this article but my preference is a modified Reflector Telescope on a Dobsonian mount (1) for ease of use, (2) value for money. They are not suitable for space photography though, as a special motorised mount is needed which allows the telescope track the object being photographed.

If you can imagine a hollow tube with a highly polished mirror shaped like a satellite dish at the bottom, an eyepiece mounted on the topside of the tube, which allows the image to be viewed, and a simple base that the tube fits into, the telescope can be assembled in minutes and is very easy to use, Our club telescope which has a 13.25” mirror was converted to this type of mount recently and has made viewing much easier, this is all contained in a special dome to facilitate viewing.

 

The first picture shows a homemade open truss Dobsonian telescope and the 2nd picture shows 3 different size standard Dobsonian telescopes. 

Basic Telescope types

2 types of telescopes are normally available, Reflectors and Refractors. A simple explanation of the difference between the two is best illustrated with sketches as follows.

 

 

 

 

 

 

A picture of a refractor telescope is shown in the next picture.

 

 

 

 

Refractor telescopes are excellent for viewing planets and terrestrial observing, however Dobsonian seems to be the choice for deep space observing.

 

 

 

Observing

For many Amateur Astronomers observing the night sky is what it’s all about, although a good few of my colleagues prefer reading to viewing.

Cork city along with most cities and towns suffers from major light pollution. Sodium street lighting and poorly designed light fittings are the main problems. Major savings could be made and much more efficient lighting at lower wattage could easily be achieved, the result would be the return of the Milky Way to our night sky in the cities.

http://www.dark-skies.freeserve.co.uk

Satellite map of night sky over Europe showing light pollution over

Industrialised regions and major cities.

 

Observing the night sky

I own a Meade 8” Dobsonian reflector telescope and I consider this to be a good telescope for anybody starting out in Astronomy, good quality eyepieces are vital and some can cost several hundred pounds, the difference these make to the object you are viewing is astonishing. Planetary detail is much clearer, wide-angle eyepieces allow objects under high magnification to remain in view for long periods.

It takes our eyes some time to adjust to the night sky, you will be surprised how many more stars you can see after 15 minutes away from the glare of lights, you will notice this even after viewing a bright object like the Moon, it takes a while for your eyes to re-adjust.

It is a good idea to plan out an observing session beforehand and be well prepared for cold weather, late night observing especially in the winter is not for the faint hearted.

1.     A typical nights observing might include the following objects, Andromeda Galaxy (M31) and its companion Galaxies, M32 and NGC 205,           (do not be put off if this seems technical)

2.     The double cluster in Perseus NGC 869 and NGC 884, superb in binoculars.

3.     Mizar in the Plough (Ursa Major) This is a celebrated double star,

     Its companion is named Alcor.

4.     The Ring Nebula in the Constellation Lyra M57. Vega, the 4th brightest star in the sky with luminosity 52 times more than the Sun is in this Constellation along with another famous double double star.

5.     Albireo, another beautiful double star in Cygnus, it is a golden yellow star and its companion is vivid blue.

6.     The Dumbbell Nebula M27, adjacent to Albireo and M57, this nebula is the remains of material and gas thrown out by a dying star 50,000 years ago.

7.     The Whirlpool Galaxy M51 in Canes Venatici, This was the first spiral Galaxy to be identified as such, back in 1845 by our own Lord Rosse using his great Leviathan telescope in Birr, this was the largest telescope in the world up to around 1900 ad.

8.     Jupiter and its satellite moons, can you identify its giant red spot?

9.     Saturn and its rings, often described as the “jewel of the sky”

 

Figure 1      Andromeda Galaxy M31

Figure 2 Lord Rosés telescope, recently restored

 My advice to anybody interested in pursuing Astronomy would be as follows.

1.     Join a local Astronomy club.

2.     Seek advice before you purchase telescopes or binoculars.

3.     Never look at the Sun through binoculars or telescopes.

4.     Get some basic books and learn the Constellations that are easy to identify like The Plough, Orion, Cassiopeia, Cygnus, Leo etc.

5.     A dark site free from light pollution makes for excellent viewing even with binoculars.

6.     Explore the Internet, it contains huge Astronomy resources.

7.     Get a monthly magazine like Astronomy Now or Sky & Telescope, these are good for beginners and expert alike and tell you what important events, planets etc. can be viewed for that particular month.

Good reading

 

The Night Sky by Patrick Moore explains the principal stars and Constellations that are visible with the naked eye. The book is illustrated with clear diagrams and has basic information on the Sun, moon, planets, comets, shooting stars and galaxies.

I would recommend Stars & Planets, Collins pocket guide as essential reading, it has easy to follow star charts and allows many deep sky objects to be located.

Philip’s Guide To Stars And Planets by Patrick Moore has slightly more advanced star charts and excellent basic information on Telescopes, The Solar System, Comets, Meteors, The Stars, Star Clusters, Nebulae and Galaxies.

The Cork Astronomy Club meets generally on the first Monday of the month in the Engineering Department, University College Cork, at 8-0 p.m. Monthly lectures are hosted both by club members and invited guests. Observing sessions take place on Friday nights at selected locations, weather permitting.

The Cork Astronomy Club’s website is Here

This contains a list of lecturers for the year, Irish and Worldwide Astronomy links, details of the current Club committee and other information.

http://antwrp.gsfc.nasa.gov/apod/astropix.html Astronomy Picture of the day

ei5fk AT yahoo.com my e-mail address REPLACE THE AT WITH @ "ANTISPAM MEASURE"

I hope that this article will entice you to enjoy a very satisfying and interesting hobby and hope to see you at a meeting of our club soon.

Charles Coughlan. Cork Astronomy Club.