- Weather Watcher ACP Manual

- C-14 Flop Stopper V2 Installation


- Ironwood Observatory Research Article

Frequently Asked Questions

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 90 x magnifications. 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.

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 finder scope?
A: The most likely cause of the problem is that your finder scope is not aligned with the main optics. To align your finder scope, 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 finder scope. Using the three adjustment screws that secure the finder scope 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: 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. Ref 1


Telescope Reviews Reviews and Classifieds

Database for 88 Constellations

Other interesting links

Copyright ©2006 Ken Archer, All Rights Reserved
Web design by CODA Studios