Q: How far can I see with a
telescope?
A: Since the
distance of a celestial object generally corresponds to its brightness, the
telescope with the largest aperture (size of the main mirror or lens) will not only
allow you to see the faintest objects but also the most distant objects. For
example, through a 60mm refracting telescope you can see the bright center of the
Andromeda galaxy which is more than 2 million light years away. With an 8"
(200mm) telescope or larger, you can see the spiral arms of the much fainter
Whirlpool galaxy, which is 35 million light years away! When using a telescope
for daytime, terrestrial observing, the distance you can see is limited by the
condition of the atmosphere through which you are viewing. High amounts of
moisture in the air or heat waves radiating from the ground will give you a
blurry image over great distances.
Q: How do you determine the
power of a telescope?
A: The
magnifying power of a telescope will change depending on the focal length of
the eyepiece you are using (see question on determining
a telescope's magnification below). A more appropriate question may be to
ask how much light-gathering power does a telescope have. Light gathering
power is a telescope's ability to see faint, distant objects (see question above) and is solely determined by the aperture of the telescope's main
mirror or lens. The larger the aperture, the more light-gathering power a telescope has.
Remember it's the entire surface area of the telescope's main mirror or lens
that is collecting the light; therefore every time a telescope's aperture is doubled, the
light-gathering power is increased by a factor of 4 times!
Q:
How do you determine a telescope’s
magnification?
A: The
magnification of a telescope changes as the eyepiece is changed. Magnification
can be calculated by dividing the focal length of your telescope by the focal
length of the eyepiece.
Always start with your lowest magnification (longest focal length) eyepiece and
work upward from there. A 2x Barlow lens will double the magnification of whatever eyepiece
you use with it. For example: using a telescope with a 900mm focal length with a 20mm
eyepiece will give you 45x magnification. Using the same telescope and eyepiece with a
2x Barlow lens will give 90x magnification. This would be the same magnification as a 900mm telescope
with a 10mm eyepiece.
Q: How can I clean the corrector plate on my
Schmidt-Cassegrain telescope?
A: The outside of the corrector plate
can be cleaned using a solution of 60% distilled water and 40% isopropyl
alcohol with one drop of clear liquid dish soap per quart of solution. The
solution is applied to a soft tissue or cotton ball and is carefully rubbed
onto the corrector plate using radial strokes from the secondary mirror
housing outward. We do not recommend removing the corrector plate. The
corrector plate is optically matched to the mirrors in alignment and in
rotation. If the inside of the corrector plate or mirrors becomes dirty, call
Celestron International and arrange to send your telescope in for a thorough
cleaning. Celestron offers complete cleaning and collimating services. Contact
the Technical Service Department at (310) 328-9560.
Q: Everything I see through my refractor is an inverted image. How can I
correct the image?
A: To correct an inverted image, you will
need a 90° star diagonal.
When a 90° star diagonal
is used, the mirror flips the image over giving a right side up but reversed
left to right image. You can achieve a fully corrected image using an erect image prism diagonal.
Q: Why can't I see anything in my telescope when I have the moon
centered in the cross hairs of my finderscope?
A: The most likely cause of the problem is
that your finderscope is not aligned with the main optics. To align your
finderscope, take your scope outside in the daylight and find an object at
least a half mile away as far away as possible (a street sign, telephone pole,
radio tower, mountain top, etc.). Center this object in your main telescope
using your lowest power eyepiece. Now look through your finderscope. Using the
three adjustment screws that secure the finderscope into its bracket, tighten
or loosen them as needed to bring the cross hairs onto the same target as is
centered in your main telescope. Your scope is now ready to be aimed at any
object in the sky and it will easily be located through the main optics of
your scope.
Q:
Where can I find a replacement battery for my 8 x 50 illuminated
finderscope?
A: The batteries used in your 8 x 50
illuminated finderscope,
PX-14 batteries and all mercury batteries, are no longer being manufactured in
the U.S. However, Celestron has introduced a new illuminator called the Pulstar Illuminator (Item
#60001) that when used with the 14mm Illuminator Adapter (Item #60006) will
work in non-threading 8 x 50 finderscopes as well as the more current 7 x 50 finderscopes.
Q: What is the difference between the Celestar 8"
Computerized and the Ultima® 2000?
A: The Ultima® 2000 is a fully
computerized telescope that has "slew to" capabilities, allowing it to move
automatically to any object in its database. The Celestar 8" Computerized has
the Advanced Astro
Master® digital setting
circle factory installed. This will allow you to move the telescope
manually as the digital display counts you down to the coordinates of the
desired object. The Advanced Astro Master® can also be purchased
as an accessory and installed onto most Celestron Schmidt-Cassegrain telescopes.
Q: I have a 60mm refractor with a focal length of 900mm. Why
can't I get a clear image when I try to use my 2x Barlow lens with my 6mm
eyepiece?
A: All telescopes have a maximum magnification of 60x per inch of aperture (under ideal
conditions). Your telescope would reach this limit at about 140x magnification. The combination you
are using gives 300x magnification (see formula above). Exceeding the maximum
usable limit will cause the image to degrade, becoming dark and washed out.
The Earth's atmosphere also plays an important part in limiting the maximum magnification you can use.
Instabilities in the atmosphere such as heat radiating from the ground and
surrounding buildings, high altitude winds, and other weather conditions can
cause your image to blur. This also explains why bright stars appear to
twinkle. The best time to use high magnification is on nights when the stars do not appear to
twinkle very much.
Q: Why don’t the images I see through my telescope look
the same as photos I see taken with the same type of
telescope?
A: Many pictures you see in magazines and
catalogs are time exposures. The camera shutter is kept open for several
minutes while the telescope tracks the object across the sky. This allows the
film to record fainter detail and colors that can not be seen with the naked
eye. In order to get similar results with your telescope, you need a camera adapter for a 35mm
camera and a clock motor.
Q: What is the difference between an equatorial mounted telescope
and an Altazimuth mounted telescope?
A: A mount is said to be "equatorial"
if one of its axes can be made parallel to the Earth's axis of rotation
(called the Celestial Pole). This is essential if you want to track an object
over a long period of time as it moves across the sky. With an equatorial
mount the motion of the sky can be cancelled out by simply turning its axis at
the same rate as the Earth's rotation, but in the opposite direction.
Equatorial mounts are necessary for long exposure astrophotography and for
using setting circles
to locate objects. Altazimuth (short for Altitude/Azimuth) mounts are the
simplest type of mount. This type of mount moves in two directions, altitude
(up and down) and azimuth (side-to-side). Due to their ease of use, Altazimuth
mounts are suited both for terrestrial viewing as well as astronomical
observing.
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As the earth rotates
around its axis, stars appear to move across the sky. A telescope on an
equatorial mount can be aligned with the earth's axis and guided to
follow objects as they move across the sky.
For more information about the benefits of an
equatorial mount, see the Telescope Basics section of this web
site. |
(607) 746-3089