Introduction
A principle aim of the Centre has always been to give the beginner help to get a good start in the hobby. We
carry that same principle into selling telescopes. Since the Galloway Astronomy Centre opened 5 years ago I
have given advice on telescopes to many of our guests. We were very pleased to become a dealer of
Skywatcher and TAL telescopes.
We have a totally unique offer for you - stay at the Centre and under our beautiful dark skies try out examples
of popular beginner telescopes such as the Skymax 127 Maksutov or Explorer-130P now with the exciting new
Synscan™ Alt Az Goto.
** See bottom of page for the list of Demonstration Telescopes **
I have been observing the wonders of the night sky for over 37 years and in that time I have used many
different types of telescope. I am impressed with Skywatcher telescopes as throughout the comprehensive
range they consistently offer very good quality at competitive prices.
It is important to remember that even though we are now a dealer, I do not intend to let that effect my
judgement when giving advice. We are happy to provide advice by phone or e-mail
Buying the right telescope need not be a gamble. Take advantage of my experience and possibly save yourself
hundred of pounds by ensuring you buy the right telescope first time. That way you will get many nights of
enjoyment not ones of frustration.
For first class service and advice phone or e-mail.
A Brief Guide to Buying a Telescope
Many telescopes are bought as a present by a partner or family member. With all good intentions they often
know little about them and makers of poor quality telescopes take advantage by claiming their telescopes
provide absurdly high magnification, such as "525x" or "675x" and with boxes illustrated with unobtainable
images. It sounds and looks good, but this is a sure sign of a poor quality telescope. The main purpose of a
telescope is not to magnify, but to gather lots of the faint light into the eye. Therefore, the larger the lens or
mirror in the telescope (known as aperture) the better the view will be. But there is much more to choosing a
telescope than that.
It is not possible to give you a complete guide in just one web page - this is why we run a 3 hour course on the
subject, but we can point out the important things you need to know.
A telescope is composed of 4 main parts -
The telescope itself, often called the Optical Tube Assembly (OTA)
The mount of which there are two types. Altitude & Azimuth (Alt Az) and Equatorial (EQ)
Finderscope used to locate the object you want to look at.
Eyepieces, these ultimately effect how large the object looks.
ALL four are important.
A poor mount even with a good telescope will wobble too much to be of use. Cheap small aperture telescopes are
simply not worth buying. If you have less than £150 to spend then the best advice is to buy a good quality pair
of 7x50 or 10x50 binoculars and a star chart (we can advise on or supply these). Use the time you take to save
more money by learning more about the night sky.
What is There to See?
Most beginners start out looking at the Moon and brighter planets (Venus, Mars, Jupiter, Saturn, Uranus). For
these object the focal length of the telescope is most critical to allow sufficient magnification of the image. It is
only later the beginner starts to look for star clusters, gas clouds (called nebula) and galaxies collectively known
as Deep Sky Objects (DSOs) scattered across the sky. It is then they discover their scope's lens or mirror is too
small to show them well. It is for these objects that the aperture of the telescope is most critical.
Telescopes – the Basics
A Refractor telescope has a lens at the front. Good for viewing the Moon and planets, but limited to brighter
DSOs. Minimum lens diameter recommended is 80mm. Large refractors are expensive and heavy, but allow
fainter detail to be seen. Short focal lengths (400 or 500mm) give a wide field of view so most objects including
planets will look quite small. Longer focal lengths of 900mm or more allow objects to be magnified more.
A Reflector telescope uses a mirror. Minimum mirror diameter recommended is 130mm. The small aperture
telescope is good for viewing the Moon and planets, but limited to brighter DSOs. A 150mm telescope will give
much brighter images allowing fainter objects to be seen more easily. Larger apertures of 200mm or more are
expensive and can be cumbersome, but will give unrivalled views of fainter DSOs. Short focal lengths (700mm or
less) give a wide field of view so again objects will look small. Longer focal lengths of over 1000mm allow objects
to be made much larger.
A Catadioptric telescope uses both a "lens" and mirror. Even small ones are expensive compared to the other
two types due to the complexity of design. For apertures of 105mm or more they do offer views of the Moon,
planets and brighter DSOs equal to very high quality refractors of a similar aperture, but at a lower price.
Mounts – the Basics
All telescopes need a mount to allow it to be pointed at the sky firmly and accurately.
A Dobsonian mount is a simple, sturdy and cheap Alt Az mount, but only sold with reflector telescopes. The
telescope can be moved left and right, up or down easily. Their advantage is that most of your money goes into
the optics. The only drawback is that the telescope needs to be moved a little bit on two axis when viewing an
object (an easily mastered technique) otherwise it will move out of the field of view due to the Earth's rotation.
An Equatorial mount is more complex and, therefore, more expensive. It allows the telescope to be moved in
only one axis to track the motion of the stars, etc. The mount can be fitted with motor drives to automatically
follow the sky. Sold with both refractors and reflectors.
There has recently been a revolution in the Alt Az design with the introduction of a good quality single arm
motorised mount. This strong, stable mount will track objects accuractely for several minutes. It is primarily for
small refractors and reflectors.
Note: Large catadioptric telescopes are often sold on sophisticated single arm and forked Alt Az mounts. But
these are expensive and not necessarily suitable as a first telescope.
Finder – the Basics
Typically, smaller telescope come with a red dot finder (RDF), while suitable for locating bright objects like stars
and planets, they can be difficult to use when finding DSOs.
Larger telescopes are fitted with a magnifying finder (effectively a mini telescope), typical sizes are 6x30 (6
times magnification with 30mm aperture) and 9x50.
Note – poor telescopes are often fitted with a tiny 20mm finderscope which is virtually useless.
Eyepieces – the Basics
Most telescopes come with "Plossl" eyepieces (EP). The focal length (FL) of the EP appears on the barrel (eg.
25mm). By dividing the FL of the telescope (eg 1000mm) by the FL of the EP the result is the magnification with
that EP.
E.g. 1000 / 25 = 40x
Only 3 EPs are needed to give a range of magnifications between 30x to 100x and if a 2x Barlow is used as well
this will double these magnifications. There is little point exceeding 150x to 200x with telescopes under 200mm
as the image becomes too dim.
Many telescopes are fitted with a focuser capable of taking both 1.25" and 2" EPs (although usually only 1.25"
EPs are sold with the telescope). This size is the diameter of the chrome barrel at the bottom of the EP. 2" EPs
are physically larger, more expensive and offer wide-angle views.
One note of caution – Ultra Wide-angle EPs, both 1.25" and 2", have become very common. While they work well
with the long FL Refractors and Catadioptric telescopes, these EPs should be avoided for the shorter FL refractors
and reflectors.
There is a huge range of EPs on the market, again we can offer advice on what best suits each type of telescope.
Some Final Notes
A telescope should be something you grow into gradually not out of quickly. A telescope of limited use is often
soon left in a cupboard.
GoTo – refers to mounts fitted with special motors controlled by a hand held computer unit. These seem like an
easy option if you don't know the night sky, but they can be complex, are more expensive and need to be set up
accurately. The new Skywatcher Synscan AZ GOTO range goes some way to providing a relatively low cost
introduction to this technology.
Buying a telescope is just the first stage additional items needed are:
Warm clothing, hat and gloves
Detailed Star Charts
Red light to read charts without loosing night vision
Moon Filter - helps reduce the glare
Light Pollution Filter - help reduce the effect of street lights
Nebula Filter – brightens stellar gas clouds (for apertures over 200mm)
Battery Power Pack - portable power for motor driven mounts
We run a course specifically to help chose a telescope which cut through the confusion of what is best for you.
Don't forget we sell gift vouchers for our Accommodation and Courses.
Purchasing
Demonstration Telescopes
Startravel 102 Refractor on EQ Mount
Explorer 130P Synscan™ Az Goto Mount
Skyliner 150P Reflector Dobsonian Mount
Skymax 127 Maksutov Cassegrain on EQ Mount
If you cannot see at least
three things wrong in this
image you definitely need
my help.
Please note that the Web prices may be out of date due to the VAT change on January 1st 2010.We will try to update the prices
as quickly as possible but there may be a difference while this is being done, we apologise for any inconvenience
caused during the changeover.
