How to Buy a Telescope
Key Attributes to Consider when You Want to Become a Stargazer
Have you ever stared at the stars at night and wish you could get a closer look? Well, telescopes can help you fulfill your wish. Choosing a telescope requires research regarding the specific use for the different types. Which one best fits your needs for your star gazing or amateur astronomy passions.
Types of Telescope
There are several types of telescopes to choose from and they include:
- Catadioptrics: combination of reflection and refraction
- Newtonian – uses a combination of lenses to reflect incoming to eye piece
- Refractor – brings light in through the lens directly to the eye piece
- Schmidt Cassegrain – a reflection telescope with a corrector plate to eliminate chromatic aberration.
For an animation of the different models go to Astro-Tom.
Refractor and Reflection Telescopes
Refractor telescopes are designed to allow light to pass through a series of refractor lenses to provide high contrast and high magnification. These telescopes primarily come in two sizes: 2.4 inches (60mm) and 3.5 inch (90mm) lenses, although larger refractors are available. The 3.5 inch is the better of the two because it has near perfect optics and much better light than the 2.4 inch..
Reflection telescopes use a combination of mirrors which reflect the image into the eye piece. The main reflector is concave mirror that tends to provide a coma effect near the outer edges of the field of view. Coma effect is when stars appear to have tails. Reflection telescopes are much lighter than refractor telescopes. The most popular sizes have 6 inch and 8 inch apertures.
How Do Telescopes Work
There a several key features that allow a telescope to work at its optimum and you need to consider these when purchasing a telescope.
- Aperture – is the opening or diameter of the lens which lets in the light and you need to have the largest aperture you can afford.
- Focal Length – the distance light travels within the telescope
- Eye Piece – has its own focal length, better telescopes they are interchangeable
- Power or Magnification– focal length of telescope divided focal length of the eye piece
- Finder Scope – essential for finding the right star you are searching for
- Photography – an equatorial mount with motor drive is critical for quality images
Support Mountings
Telescopes use a variety of mounts for support. These types of mounts include:
- Cradle – this type of mount allows the telescope to be placed inside to provide support
- Tripod – the telescope is attached to the top of three legged support
- Equatorial – this mount follows the apparent movement of a star as the earth rotates
- Altazimuth – this mount allows adjustment of azimuth and altitude to find a specific location in the sky
- Unmounted -- the telescope is not mounted and used for a variety of purposes
Considerations for Use
The efficient use of a telescope is accomplished best when the night sky is night overwhelmed with city lights. If you are serious about astronomy and looking at the stars you need to get as far away from city lights as you can. These telescopes are designed to receive light and bright city lights have an adverse affect.
If you are serious about viewing the moon, stars, and planets do not purchase your telescope from a toy store or department store. Their quality is questionable and you will be disappointed.
