One question many newcomers to the hobby ask is “What kind of telescope do I need?” In terms of getting started, the answer is “None!”
Astronomy can be done with no optical aids other than the naked eye
However, naked eye astronomy, whilst it is fun and very educational, may leave the newcomer wanting more, and the best purchase at this point is probably a decent pair of binoculars.
Good binoculars for astronomy will have a number of features. Firstly, since astronomy is generally (but not always) conducted in the dark, it will be useful to have good light gathering power. Secondly, a reasonable degree of magnification is required to give the effect of getting closer to astronomical objects which are all very far away.
Binoculars are specified by two figures – being the magnification and objective (front) lens diameter. A good specification to start with is 10 x 50. That is 10x magnification, which is about as much as a steady hand can hold still enough, and objective lenses of 50mm diameter.
A bit of optical theory will be useful at this stage. The eye has a pupil that lets light in and has a diameter of approximately 7mm in a young adult. Sadly, as with many things, this declines with age and as we get older this will drop to around 5mm. This should ideally be matched to the exit pupil of the optics used, and this figure is determined by dividing the objective diameter by the magnification.
In the case of our 10x50 binoculars we can see that the exit pupil is 5mm, so an older person will make full use of the light gathered by such optics while a younger person may get some additional benefit from a 10x70 pair, though these would be bigger, heavier and hence harder to hold steady.
There are many binoculars sold for travel purposes which are very compact and achieve this compactness by having much smaller objective lenses – 10x25 being a common example of the type. These have an exit pupil of 2.5mm and as such are not really suitable for astronomy. The Moon is bright enough to look OK through them, but that’s about it! For similar reasons, anything with a zoom function – such as 10-30x30 – is best avoided – the light gathering and optical quality are almost always compromised.
There are bigger binoculars – 15x70 is a popular and useful increase in magnification and light gathering, but they get harder to hold still with the increase in size, and beyond this level some form of mounting becomes essential. We’ll leave this until we’re looking at more advanced setups.
The other consideration with binoculars will be cost, and this is generally tied in with the quality.
Whilst the old maxim “you get what you pay for” remains largely true, the fact is that in recent years Chinese suppliers – often under “western” brand names, have made available very acceptable binoculars at reasonable prices which while not quite as good as the best, are perfectly good enough for the beginner. Particularly the Meade and Bresser lines sold through the Lidl supermarket chain for about £15-18 are well worth the money. Don’t expect the same quality as Pentax and Nikon because they will start at 10x the price, but you do get decent glass with adequate coatings.
You will see a lot with binoculars, from craters and maria on the Moon, to phases of Venus and the Moons of Jupiter. Open star clusters like M45 (the Seven Sisters) and M44 (the Beehive) will look impressive, though sadly the rings of Saturn need just a bit more magnification – about 30x being the minimum that will show these.
If you get more serious about the hobby and want to start thinking about telescopes, then it’s a bit of a minefield. Two reasons – there are so many choices to be made depending on your interest, on practicalities like storage and transportation, and secondly, because there is sadly a fair bit of rubbish on the market.
Think through your needs and buy carefully though, and there is plenty of quality equipment available.
There are three main designs of telescope to choose from, and then there are options for mounting them including computer controlled motorised drives of varying degrees of complexity, added to which is a plethora of eyepieces, accessories, cameras and all sorts!
Refractor – uses a lens to create a virtual image which is then magnified by an eyepiece
Reflector – uses a mirror to create a virtual image, magnified by an eyepiece, usually with a secondary mirror in between
Compound – uses a combination of lenses and mirrors.
Then there are two types of mount:-
A very common variation on the Alt-Az type mount is the Dobsonian, named after its inventor, John Dobson http://en.wikipedia.org/wiki/John_Dobson_(amateur_astronomer)
This is designed for simplicity and is a very convenient way of mounting a Newtonian Reflector such that portability, ease of storage and ease of pointing are all optimised. The downside is that this is generally a totally “manual” telescope – you will need to learn the sky to be able to find objects with it, and you will need to learn how to move the scope to follow them as the Earth’s rotation moves them through the sky. For those purely interested in observing objects, this type of telescope offers the maximum bang for the buck with a good 8” scope starting at under £300.
There are also many Alt/Az based scopes which are of the so-called “Go-To” variety. These come in all sizes but at the starter level can be short-tube refractors, reflectors or compound scopes. These scopes are controlled by a small computer which controls motors that move the scope on its mount and can take you on a guided tour of the night sky and show you many more objects in a night than you’ll see if you have to find them yourself.
The downside of this marvellous technology of course is cost. You are spending most of your money on technology and less on optics, so a 3” or 4” scope of this type will probably cost more than the 8” Dobsonian and as a result it will ultimately be less capable. And of course, by leaving the computer to do the finding, you won’t be learning the sky! The Meade ETX range and Skywatcher Synscan scopes are examples of this type of scope and prices start at £300 for a Skymax 102 4” Maksutov-Cassegrain scope with Go-To.
In terms of deciding what to buy, a good way of seeing different scopes in action is to come to our Observing Nights where there will be various scopes in use, up to and including the IAA’s 16” Meade Lightbridge – a powerful light gathering optic that can pull in dim deep sky objects, and also smaller scopes owned by members. And of course you’ll be able to draw on the collective experience of many of members whose interests cover the full range of observing and astrophotography.
And where to buy? Well generally department stores and generalist websites are best avoided unless you are sure you know exactly what you want and want the best price without any guarantee of after-sales service.
A better option would be to talk to Dr Andy McCrea, proprietor of North Down Telescopes. As well as being Editor of the IAA magazine “Stardust” and a past-President of the IAA, Andy is an accomplished observer and astrophotographer of many years experience so the advice doesn’t come any better and he can get a wide range of gear delivered to anywhere in Ireland, North or South, at very competitive prices.
Whichever path you choose, enjoy the hobby!