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Equipment for the
Amateur Astronomer
By
Gary Nugent
Binoculars and
telescopes and other astronomy equipment and accessories are
the meat and potatoes of amateur astronomy. A good pair of
binoculars is what introduced me to the pleasures of
stargazing many moons ago and only after a couple of years
scanning the skies did I graduate to a telescope. That was one
of the department store 60mm telescopes we're all warned
about, but my folks didn't know any better, and to a 12-year
old kid, it opened up the universe.
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Telescopes
While cheap (in every sense of the word) telescopes are still
to be found, recent years have seen the introduction of small
but very affordable telescopes from manufacturers such as
Meade and Celestron and, despite their small size, these
telescopes have excellent optics that far outperform the cheap
optics in my old 60mm scope from so long ago.
Many of these
small telescopes now come with GOTO features that allow you to
select an object to view from an attached handset and the
telescope will automatically slew to that feature in the sky.
What the ads tend to forget to mention is that in order to use
this facility, the telescope must be correctly set up and
aligned beforehand.
Many scopes,
unfortunately, lie gathering dust in corners and wardrobes
because their owners couldn't figure out how to use the thing.
It's not their fault - better, and simpler, instructions
should be supplied with the telescopes. But for those who can
work with such an instrument, a wealth of celestial objects
are available for viewing that would be quite difficult to
find otherwise.
Some old hands
in astronomy societies have welcomed the new technology
openly, others have decried its introduction as it stops
newcomers from learning their way around the skies using a
technique called star hopping. In some ways, they see that
there must be a little pain in finding an object before you
can have the pleasure of viewing it. I suppose it's a bit like
the difference between being bussed to Machu Pichu or going on
a five-hour hike up the mountain to see it. Which would you
choose? If the hike is your cup-of-tea, then star-hopping is
for you.
Personally, I
think the introduction of GOTO mounts has been a very positive
development and has made the hidden beauty of the night sky
accessible to many more people. If you've bought a small
telescope with an integrated GOTO mount yourself, but are
unsure of how to use it or the best objects to view, go along
to your local astronomy society or club and ask their help.
They'll be only too willing to lend a helping hand.
On the other
hand, if you do want to develop a knowledge of the night sky,
then a simple Dobsonian telescope is a good place to start.
These 6-inch and larger reflecting telescopes come on simple
mounts that allow you to pivot the telescope left and right
and up and down so you can easily point it anywhere in the
sky.
The
Choosing a Telescope
article by fellow amateur astronomer Kevin Berwick discusses
the different types of telescope that are available and
provides sage advice on what might best suits your needs.
Eyepieces
You should have a selection of eyepieces to use with your
telescope to allow close-up views or wide-field views. Planets
require small diameter eyepieces to see surface detail whereas
larger subjects, like the Pleiades and other large star
clusters require wide-field views. Pretty much any eyepiece
can be used to get a good view of the Moon or close-up views
of it.
Eyepieces range
from about 3mm to 40mm (i.e. the glass in them, not the
diameter of the eyepiece itself!) and come in three fittings:
0.965", 1.25" and 2" (for high-end telescopes). The 0.965"
fitting is seldom used these days but older telescopes used
eyepieces of this size. There are also different types of
eyepiece: Plossl, Erfle, Kellner, Orthoscopic, wide-angle,
etc. The magnification an eyepiece provides depends on the
focal length of your telescope - divide the telescope focal
length by the eyepiece size to get the magnification. A
typical refractor (uses lenses rather than a mirror) has a
focal length of about 900mm. A 26mm eyepiece would provide a
magnification of 34x with this scope. Used with a telescope
with a 2000mm focal length, the magnification is 77x.
There's another
feature of eyepieces called the Field of View. Basically, this
is how big an area of sky is seen through the eyepiece. The
bigger the field of view, the more can be seen. How much of
the sky is seen depends on the eyepiece diameter and the focal
length of the telescope. Wide-angle eyepieces (82 degrees
field of view, for example) tend to be quite expensive.
Average eyepieces, such as Plossls, have about a 50 degree
field of view. Wide-angle eyepieces can almost give the sense
of �being out there�.
Binoculars
While this discussion has centered mostly on telescopes,
binoculars have a role to play in astronomy as well. A quality
pair of binoculars costs less than a telescope and is a good
entry point for someone familiarising themselves with the sky.
They don't offer the same magnifications as a telescope (but
magnification isn't everything) but they do show a much wider
field of view which makes it easier to navigate across the
sky. Because of this wider field of view, you also get to see
the 'big' picture. And, because you're using both eyes,
there's less eyestrain.
You can get
binocular viewers for telescopes and those who use them (even
though they cost a few hundred dollars and you need two of
every eyepiece) swear by them (rather than at them!). A
typical set of binoculars will be 10x50s (front lenses 50mm
across, with a x10 magnification). More powerful models are
available - 20x60s are available from $150 upwards and you can
get 20x80s for as little as $215.
These binoculars
are quite heavy and you can tire easily pointing them skyward
for any length of time. Also, because of their higher
magnification, any shake in your hands will also be magnified
and stars will dart around in the view. For long-duration
viewing, you'd be advised to get a tripod and a binocular
tripod adapter which lets you securely mount the binoculars on
it.
Binoculars are
also great for looking at large scale celestial objects such
as comets. Looking at the Moon through 20x binoculars brings
it close enough to see topography but also, you'll see it in
three dimensions, something lacking when looking through the
eyepiece at a telescope. You can whip out a pair of binoculars
much more quickly than setting up a telescope so if you have
very changeable weather where you live, they might be a better
option for sky viewing. Of course, you can throw a pair of
binoculars into your luggage very easily and view the sky from
your holiday destination with ease.
Gary Nugent has
spent more years than he cares to remember pursuing astronomy
as a hobby, either running astronomy clubs, pubishing
magazines or writing astronomy software. He's run the Night
Sky Observer astronomy websitehttp://www.nightskyobserver.com
for over eight years.
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