Astrophotography telescopes are available today thanks
to two great scientists. The first was Galileo Galilei who invented the refractor telescope about 400 years ago
using a lens at one end and an eye-piece at the other. This design is still in use today and is popular with
A good starter telescope in this range is 60-90mm on an alt-azimuth mount (meaning it moves up and down (altitude) and
side to side (azimuth)). Refractor telescopes in this size-range are inexpensive but will bring out good
detail on the Moon. Larger refractors can be problematic and false colour can occur, known
as 'chromatic aberration'. A good choice, if you're looking for an inexpensive way to get started in astrophotography.
Amazon have a good range of refractor telescopes many
under $100 and starting from as little as $25.49.
The development of astrophotography telescopes took a new turn when Sir Isaac Newton invented the
reflector telescope which uses mirrors instead of lenses to gather light. Although considered
better than refractors as they offer more light-gathering power
per dollar, there are a couple of drawbacks.
Firstly, they have to be cooled down to match the
temperature of the night air before they can be used; patience is required! And secondly, they
have to be re-aligned from time to time. Amazon's
also start at well under $100.
In the 1960s, an amateur astronomer called John Dobson invented a telescope with
a large objective diameter (for greater light-gathering power) combined with portability
for travelling so he could set up in places where light pollution was absent. He used
simple and inexpensive components in a design which is used today for a whole
range of wide-aperture reflectors.
John Dobson's design is ideal for observing dim, deep-sky
objects, particularly as it has a large aperture, and because Dobosnian telescopes are
made of light-weight materials.
Dobsonian reflector telescopes up to eight- or ten-inch aperture can be handled easily
by one person while being large enough to show hundreds of galaxies and resolve globular
clusters into thousands of individual stars.
Dobsonian mounts support a telescope in the same way a canon is mounted. However, there is another
method known as an equatorial mount (sometimes called German Equatorial Mount)
which uses counterweights to balance the telescope. This type of mount lets you track
stars and planets with a slow-motion knob or with a motor drive. Good equatorial mounts
are more expensive but will keep celestial objects centered in the eyepiece - essential
Follow the link to find out more about
German equatorial mount telescopes.
Putting it all Together
Catadioptric telescopes use a combination of mirrors and lenses to effectively 'fold' the
optical path into a shorter tube making them very light weight. This modern design works well with computerized mounts
enabling you to easily find stars, galaxies and nebulae.
The only drawback is the high battery consumption so you need to use rechargeable batteries unless you have it plugged in to the
mains or your car cigarette-lighter. Catadioptric telescopes are a good buy as they combine
power with portability. To see the Amazon's best-selling catadioptric telescopes, click
the link - updated hourly.
If you want to make photographs with your telescope, my advice is to purchase the one with the largest aperture you can afford
and preferably with a computerised 'goto' function for simplicity of use. There are two types
of computer control, one where you move the telescope until the attached hand-controller
says you are on target and the other which has a motor-drive that does all the work.
Also beware of manufacturers who claim 500 times magnification for small telescopes - anything
at that magnification will be fuzzy.
The maximum useful magnification is roughly 50 times the aperture in inches or
twice the aperture in millimeters.
Finally... a T-adapter and a T-ring are required to mount a camera on astrophotography telescopes.
T-adapters allow you to attach your 35 mm SLR camera to the prime focus of your telescope.
This arrangement is used for terrestrial photography and short exposure lunar and planetary
photography. It can also be used for long exposure deep-sky photography.
T-ringsconvert the camera's mount to a standard T-thread, allowing you to couple the body
of your camera to a camera adapter or, in some cases, directly to the focuser of a telescope.
Oh, and a final, final bit of advice concerning eyepieces. A good eypiece is one of the most important parts
of your telescope
but don't buy zoom eyepieces as the only good ones are really expensive - around several
hundred dollars! To enhance magnification of your eyepiece, you can attach a
which will double, triple or quadruple the magnification.