If that’s so, you’re lucky as I have the same intentions and have done some research about purchasing telescopes, their specifications and what do they imply.
Here are some of the more important aspects : -
- Aperture – The most important part, i.e. the width of the opening (in mm) where it dictates how much light goes in, and therefore how good the images in your refractor are.
- Focal length – the length from the point where light are collected to the point where all the light are focused. If you studied optics it’s the point from the aperture to the focus.
- Focal ratio – the ratio of the focal length / diameter. Generally used to show what the telescope is suited for. A f/ratio of <6 is good for deep sky stargazing (nebulae, galaxies, etc.) 6>f/ratio>10 is good for general viewing, while f/ratio>10 is good for lunar and planetary viewing and mapping.
- Magnification – Each telescope generally has eyepieces that can be interchanged. The focal length of the eyepiece changes the magnification of the telescope, a shorter focal length gives a higher magnification. The equation goes like this : Magnification = Focal length of objective (Telescope) / Focal length of eyepiece. Beware that higher magnification doesn’t mean the telescope is better, if your telescope do not have enough aperture length to let enough light in, your excessive magnified image will be very blur and unusable.
- Mount – there are two main types – equatorial and altazimuth. The equatorial makes use of the R.A. – Declination coordinate system and is very good for tracking celestial objects. If you’re in Malaysia or the equatorial region, the equatorial mount is the right one.
Of course, this is what I so far understand about the refractors. If you find any discrepancies please comment below. After all, this article is to help you, me and everyone else in understanding more about telescopes before taking the plunge into actually owning one : D.
