|Choosing Your Astronomical Telescope|
If You are a newcomer to the world of Astronomy or you want to buy someone a telescope as a gift,
then this section is here to help you to decide which one is best. You can email questions on our Contact us page
or call us if you are still undecided.
Before we progress to the various types of Telescopes and their Mountings, take a moment
to look at the following key points which will help you to decide
£ Your Budget
Decide what the maximum budget will be that you wish to spend and bear in mind that the more that you pay,
the better the quality of build and optics will be. At SBTC we strive to sell only
the best value for money telescopes at the lowest price possible.
Sometimes it is better to test the water by buying an inexpensive telescope and sometimes it may be better
to stretch the budget a little, especially if the person has had an interest for a long time and you know
that it is not just a passing phase!
If it is for a junior person then perhaps you would like to visit our Junior Section.
Weight and Size
The larger the diameter of a telescopes main Mirror or Objective lens, the more light it gathers and therfore
the more detail it will show in your eyepiece, especially when viewing deep space objects like Galaxies,
Nebulae and Star clusters.
A 130 mm Reflecting telescope will gather approximately 400x more light than the naked eye wheras
a 150mm scope will gather approximately 625x more light.
Heres the catch! Because the bigger the aperture of a scope, the bigger and heavier the instrument and it's mount
and tripod will be.
So you need to consider the portability and storage of the telescope and if it fits in with your own situation.
Myths about Magnification
All our telescopes are chosen for their correct usable magnifications.
To get breathtaking views of the Moons craters and the rings of Saturn only requires about 100x magnification.
Star fields, Galaxies and Nebulae only need a low magnification and are best viewed at a lower magnification
as it is brightness of image that allows us to see these fainter deep space objects.
Some catalogue shops and department stores that know little about scopes will sell telescopes with very high
magnifications like 600x.
We certainly would never sell such telescopes and they will not give good results at all.
|The Equatorial Mount|
The Equatorial Mount at first glance is complicated with lots of twiddly bits! but once you know the concept of how it works,
you will quickly realise that it is actually built to make your life easier.
The Equatorial mount as it's name suggests is a device to allow you to track your telescope in the
same plane as the Earths rotation.
This allows you to track the telescope either manualy or by adding a motor drive to track automaticaly.
As the Earth rotates,the object that you are viewing through a telescope will seem to be moving but of
course it is us that is moving and the equatorial mount will track in the opposite direction of the earths rotation.
This opens up other possibilities like taking long time exposure Astrophotography
|The Altaz Mount|
|The Altazimuth Mount|
The Altazimuth or Altaz mount is a bit more basic and also lighter in weight due to the fact that it does
not have heavy counterbalance weights.
This mount gives up and down and right and left movement and cannot track in one motion like an
equatorial mount does.
It is the perfect choice for someone that wants a no fuss and portable mount and can be used for on land
or terrestrial viewing with a refractor or Maksutov style telescope. It is not really suitable for use with a reflecting
telescope with some exceptions.
|Computerised Telescope Mounts|
Computer driven mounts have become increasingly more popular especially for people who already have an
interest in computer technology. They have revolutionised the telescope and give a lot of pleasure in that the user can
now spend more valuable clear sky time actually looking at objects than searching around for them.
The concensus was when they first appeared on the market that it takes the fun out of finding objects in space
but everyone has different opinions about that.
With these type of mounts after a few minutes of initial set up the rest of the night is yours to choose
objects from the handset menu and press "Go -To" when the telescope mounts motors swing into action
and take you to the object selected.
Computer mounts are now available in Altaz or for Equatorial Mounts.
|The Newtonian Reflector Telescope|
Pound for pound, the Newtonian reflector telescope is better value for money if just starting in Astronomy
with more size of Aperture for your money than other counterparts. A versatile instruments which will
yield good images for Lunar and planetary viewing as well as deep space observing. These are not suitable
however for any land or terrestrial viewing as the view is inverted and viewed at 90 degrees
These days the silvering on mirrors is coated with a silica overcoat which stops the silvering from oxidising which
used to be a major problem with reflector mirrors. Now mirrors can last for many years before
the need for cleaning or resilvering.
Refractors employ an objective lens at the top of the tube to project the image down to the eyepiece.
They are generaly very good for Lunar and Planetary work with even small 60mm refractors giving good views
of the Moon,Saturns rings and Jupiters cloud belts
A refractor telescope mounted on an Altazimuth mount would be ideal if you wanted to use the telescope
for both Astronomical and Terrestrial viewing with the addition of an erecting diagonal to turn the image
correct from left to right.
|Maksutovs and Schmidt Cassegrains|
|Maksutovs and Schmidt Cassegrain Telescopes|
The Maksutov and Schmidt Cassegrain telescope uses a combination of Mirrors and lenses to fold the
light path of the image up and down the tube. This allows for a longer focal length system but with the benefit of a compact
more portable instrument.
These have become very popular today but do tend to be more expensive than a Refractor or Reflecting Telescope.
A Maksutov has a lens at the front whereas a Schmidt Cassegrain has a Thinner Corrector Plate.
Sometimes in very cold weather the front lens or corrector plate can dew up and you may find it necessary to
wrap a dew shield around the front of these instruments. These can be purchased or simply improvise with some
plastic sheet and a little velcro!
|The Dobsonian Telescope|
The Dobsonian Telescope is essentially a Newtonian Reflector Telescope (Usually a long focal length one)
Mounted on a very simple wooden mount arrangement which allows for up and down and right and left movement
similar to an Altazimuth Mount. Often refered to as a "Light Bucket" these telescopes are an economical way
to own a large aperture telescope at a lower cost than telescopes on other mounts.
Finding your way around the sky with a manual version can be tricky but is something that comes with practice
and once achieved can be very rewarding with Breathtaking views of the night Sky especially if the budget will
stretch to an 8 or 10 inch aperture model.
Nowadays some dobsonians have had a makeover with the addition of Motor drives for tracking and even
computerised versions that will find and go to any object that you select from the hand control menu.
An ideal scope to pack away on the back seat of the car and take off to the hills with!
If you have some restricted views from your garden like trees or bushes and you wish to mainly use from the
garden then just bear in mind that because of the low angle of projection that there are restrictions of view
when compared to an Equatorially mounted telescope that is set higher from the ground.
|THE POWERS OF A TELESCOPE|
|The Powers of a Telescope|
Light Grasp or Light Gathering
The main function of the telescope is to gather light or amplify light and this is done by the use of dish
shaped lenses or mirrors to concentrate the rays of light from the subject on to the eyepiece of the telescope
where the eye picks up the final image.
The wider the aperture or diameter of the primary lens or mirror, the more that the telescope will show up in detail
and the fainter magnitude of stars and other deep space objects will be shown.
How much magnification that you need will depend on what subject you are viewing.
It is the Eyepiece that gives the magnification of the image and the eyepiece can be
changed as and when needed.
The focal length of the telescope divided by the focal length of the eyepiece will give the magnification.
For viewing stars and other deep space objects a low magnification is required. This is so that the image
brightness is efficiently amplifying the faint object and bringing it in to view (High mag is not needed for stars)
If you are viewing the Moon or Planets then a higher magnification eyepiece can be inserted in to the focuser
because these solar system objects can be magnified. Always try to stick within usable or optimum
magnifications as stretching the magnification too high for a particular size of aperture will only
result in poor quality images.
The general rule of thumb is 50x magnification per inch of Aperture of your primary Mirror or Objective lens.
|Telescope Resolving Power|
The Resolving power of a telescope is it's ability to show fine crisp detail of lunar and Planetary subjects
like Saturns Rings and the polar caps of Mars and Double stars at higher magnifications.
Generaly the longer the focal length of a telescope the better the resolving power, therefore long focal length
Refractors and Maksutovs are good performers and a good choice if your main interest is Lunar and Planetary work.
Always bear in mind though that even if your main interest is in Lunar and Planets that there are many more
millions of objects outside our solar system to see and the planets are not always well placed to observe so to
get the most out of a telescope all year round,
choose carefully but take note that all the telescopes that we sell are good but some are better than others
in slightly different ways.
Whatever your choice Enjoy!
If you have any questions then please do not hesitate to use our contact us form
The Skywatcher instruction Manuals, available on the Skywatcher website may be useful reading for You.