Telescopes FAQ

Do I have to be an expert in astronomy to enjoy using a telescope? How can I locate interesting objects to observe?

Most first-time telescope users know little or nothing about the night sky, and you certainly do not need a course in astronomy to enjoy your telescope to the fullest. Begin with the objects easiest to find: the Moon, Jupiter, Saturn, Venus, and Mars. All of these are bright objects even in the midst of a big-city environment and can be located by using star maps in popular monthly magazines such as Astronomy or Sky & Telescope. 

Do I need to take my telescope out in the country, away from city lights, to realize its full potential?

Some types of objects (e.g., nebulae and galaxies) are best observed in a dark-sky environment, although even many of these are clearly observable through small telescopes in the city. The Moon and planets, by contrast, can be studied about equally well from the city or country. The basic rule is that while observations made outside the city generally reveal more detail, particularly in deep space, there are still a great many objects within the grasp of a small telescope in urban areas. 

Does Bushnell have any hints for beginners on viewing through a telescope?

Certainly, here is an excerpt from one of our publications:

For beginners it is best to put in some practice by viewing terrestrial objects during the day. Initial experience can be gained during this time of the operation and use of your telescope. If your telescope is equipped with a moon filter, be sure to remove it from the ocular, do this before viewing objects and only use the filter(s) for their intended use.

Never mount more than one accessory (except moon filter) with your ocular lens. This shifts your focal length and prevents you from getting a proper focus, (Example: Barlow and Star Diagonal, 2Omm ocular lens.

Let's talk about POWER: It's a natural tendency for all of us to want to magnify the moon, planets and stars as much as possible so as to be able to see it as closely as we can. Wouldn't it be wonderful to see the "canals" on Mars or the ice cap on Jupiter or the Apollo landing sights on the moon?

Yet, the pure and simple physics of light transmission, refraction and magnification through optical lenses make this a very challenging task. As one seeks to increase magnification of an image, more and more of the light is lost or reflected. And as more magnification is achieved, the more interference occurs from ambient or casual light sources, as well as from the atmosphere itself. That is why the more experienced telescope user knows that viewing is generally more enjoyable at lower powers.

That is why we suggest you begin learning about your new telescope by starting at the lower powers. After you gain some skill and practice at low powers, you can carefully move up when viewing conditions are best.

By starting with the lowest powered ocular lens, this allows you to focus in and find objects prior to using the higher powered oculars (5mm, 6mm, 4mm or 2x Barlow) produces a smaller field of view. If the image is fuzzy at higher magnification, drop down to a lower magnification as the atmospheric conditions are not sufficient to support the high magnification at observation time. Remember, the higher the number on the ocular, the lower the power. To figure the power of an ocular lens you divide the number on the ocular into in to the focal length of the telescope. (Example: 700mm/20mm=35x). Avoid touching or jarring the scope while viewing. This results in vibration that causes the image to shimmy or move. Also make sure that all assembly screws are secured as tightly as possible. When viewing at night, allow at least 15 minutes for your eyes to become adapted to the dark. If you wear glasses, remove them when viewing through your scope unless you have an astigmatism. 

How do I determine the power of my telescope?

The power of your telescope can be determined by dividing the focal length of the objective lens by the focal length of the eyepiece. The eyepiece focal length is the number printed on the eyepiece (for example: 1000 divided by 25=40X).

How do you align the finderscope?

Aligning the finderscope can be accomplished following these steps.

  1. With the 2Omm eyepiece in place, point the telescope at some well-defined land target (e.g. a telephone pole or building) at least 200 yards away. This may be done manually or by using the fine tracking controls (control knobs). With target object centered in the field, tighten the control lock knobs.
  2. Look through the finderscope and tighten or loosen, as appropriate, the finderscope's alignment screws until the crosshairs of the finderscope are precisely centered on the same object already centered in the telescope's field of view.
  3. Once this is accomplished objects located first in the finderscopes field of view will also be centered in the main telescope. (Note: the image presented by the finderscope will be upside-down and reversed) 

My equatorial mount telescope seems unsteady, how can it be stabilized?

Properly balancing the scope will make it easier to work with. Use the following steps to help you out.

  1. Arrange the telescope so that the telescope body is horizontal to the floor (latitude of 0 degrees). Loosen the R.A. (right ascension) lock-knob. With R.A. lock loosened, the telescope mount will turn freely about the polar axis. Rotate the telescope about the polar axis so that the counterweight shaft is parallel to the ground (horizontal).
  2. Loosen the counterweight's lock screw, and slide the counterweight along the shaft until the telescope remains in any given position without tending to drift in either direction. Then re-tighten the counterweight lock screw to lock the counterweight in position.
  3. To balance the telescope about the declination axis. First loosen the declination lock knob, then slightly loosen the clamp ring screws so that the telescope main tube can slide inside the rings. Slide the main tube up or down inside the rings until the telescope is balanced about the declination axis. Re-tighten the clamp ring screws. The telescope is now balanced. 

What are the best conditions for observing?

Good or poor viewing is not always determined by the optics of a telescope. There can be external factors determining the quality of an image. The blanket of air surrounding the earth is constantly in motion. This shifting and swirling of the atmosphere causes a poor image especially at higher powers. This constantly changes so some nights may be better for viewing than others.

Optical distortions made by the rippling of air currents emitting above a heated surface or area can cause a poor image. Objects are more distinct when viewing straight up because you are only viewing through an atmosphere of about 10 miles thick. This is opposed to an atmosphere 15 miles thick at 45 degrees, and over 100 miles thick near the horizon.

Light pollution: If possible avoid using your scope around lights (street lights. house lights. etc.). A high magnifying telescope is very sensitive to light, resulting in a washed out image or an annoying glare. The effects of bright light become more obvious near cities. Many of the stars seem to disappear near the city horizon.

Moonlight can be another factor. The harsh glare from a full or bright moon can dim nearby stars and planets. The moon itself is best viewed during the phases near the area dividing the darkness and sunlight.

Avoid viewing through an open window (never view through a closed window). The air currents caused by the inside/outside temperature, especially during the cold season makes quality observation impossible.

A bank of clouds is impossible to view through. Fortunately these are constantly moving. When stars twinkle rapidly, this is a result of the warm and cool air mixing. This results in poor viewing. Try to observe on nights when the stars have a steady 'burn' like the planets. A heavy haze causes poor viewing but a faint haze usually means a still atmosphere and good viewing may be possible. Stars always appear as pinpoints of light. They are at such great distances that any discernible size difference between very low and high magnifications within the telescope is impossible. The light gathering power of the telescope allows you to see stars and planets that your eyes would not normally see within the solar system.

Most telescopes give their widest field of view at lowest power - usually not more than 1-1/2 degrees. This means it is frustratingly difficult to find anything in the sky with the telescope alone. A small telescope called a finderscope is mounted parallel on the side of the main scope to get around this problem. The low powered finderscope with its four to six degree field of view and central crosshairs permits precise aiming before you look through the main body of the telescope. 

What can I see with my telescope?

Telescopes with power ranging from 25X to 50X can be used to view Star Clusters and Nebulae. 90X to 120X telescopes can view galaxies. Most planets can be seen at 150X and higher.

What do the numbers on the eyepiece mean?

The numbers of the eyepiece represent the focal length of the eyepiece. 

What is the difference between a Refractor Telescope and a Reflector Telescope?

Refractor telescopes use lenses only (no mirrors or prisms). The refractor is essentially a closed tube design. It is mechanically uncomplicated and basically maintenance free. Refractors are generally used for astronomical viewing; however, they can be used for terrestrial purposes beyond 100 feet. 

Why is the image in the telescope upside down and reversed from right to left?

An upside down and reversed image is a common characteristic of most astronomical telescopes. Since telescopes are used for astronomical viewing orientation is not important. The image in the finderscope will also be upside down and reversed.