Telescope Type in Depth
are Newtonians reflectors that use a concave parabolic primary mirror to collect and focus incoming light onto a flat secondary (diagonal) mirror that in turn reflects the image out of an opening at the side of the main tube and into the eyepiece. In layman's terms, a reflector telescope uses a large mirror at the bottom of the telescope to focus light rays on a smaller mirror near the opening which then reflects the light into an eyepiece located at the top of the telescope. The Newtonian reflector is the oldest reflector design in use and still the most popular reflector telescope.
** This is the layman's term for "reflector telescope."
** Produces much better quality images because the color reproduction is more accurate and there is often little or no chromatic aberration.
** Because of their design, with the focuser on the front, they are easier to use than refracter telescopes.
** These are good telescopes for the money. The quality is as good as with an achromatic telescope. Basically, they are a good all-purpose telescope.
** They can collect dust and dirt, and they need periodic recollimation.
** You may also be interested in Maksutov Newtonian Telescopes
** Maksutov Cassegrain
by Questar. These are like the Schmitt but better as far as contrast goes. Plus they have big apertures and are reasonably priced for what they offer, including sharp images, portability, and larger eyepieces and focal lengths.
*** Expensive compared to the aperture offered.
*** Wide field of view is restricted because of the large focal length.
*** Subject to dew and moisture like the Schmitt Cassegrain.
The Details About the Features
* This is such an important element to consider when buying a telescope. So what is aperture, you ask? It is much like camera aperture. It is the opening in the lens which allows for different amounts of light to enter into the barrel. The more light that comes in, the better the image you will see.
** You will see aperture labeled in millimeters and rarely in inches, and the rule of thumb is bigger is better.
** Optical quality and mounting is of prime importance as well.
* '''Magnification''', which often is an improper indicator of a telescopes power, should not be mistaken for aperture. A way to compare telescopes without making this mistake is to multiply the aperture by 50x. That will give you an adequate idea of the actual magnification you will achieve.
* Focal length has a lot to do with how much magnification power you have.
* By dividing the lens diameter of the eye piece into the focal length you will get the magnification power.
* Stability is important. You don't want anything that shakes or jiggles. Preferably, the tripod should be a strong altazimuth mount, instead of an equatorial mount.
** '''Dobsonian''': Dobsonian mounts
are made for telescopes with Newtonian lenses. They are inexpensive, made with wood and nylon and Teflon bearings, and can even be made at home. Because they are made to sit low to the ground, they are very stable as they sit on a swiveling base.
** '''Altazimuth:''' equatorial
mount design is slightly more cumbersome to use because it only moves along the polar axis, ie, horizontally. Any vertical adjustments then need to be made by hand.
* Lenses, or eye pieces, are made by Plossl
* You will often see the degree-field and the number of elements an eye piece has. Again, more is better.
* Solar and nebula filters can be purchased to observe deep-sky contrast as well as the sun.
* Eye pieces should be 1.25" or 2" in diameter, which is not only standard, but also compatible with the best quality replacement lenses.
* These are used like mini-scopes. They sit on top or on the side of the telescope and are used to view large portions of the sky at a lower magnitude to help you locate where it is that you want to zoom in on.
* Some telescopes now feature "auto-finders" that have a stored database of where things are located so that it saves you time looking for them. Autostar is one such series that features this. Some telescopes come with them and some don't. Either way you can purchase one for about $50.
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