Telescopes
| Advantages | Disadvantages |
| Standard-quality achromatic or apochromatic refractors have some advantages over other telescope designs. Firstly, refractors, by default, bear a totally clear aperture. There is no central obstruction that leads light to be distributed from brighter to darker areas. So, the visitor can experience a better contrast in refractors. In these telescopes refractors often are adduced as the premier instruments for a planetary and double star observation. Low maintenance is the second advantage of refractors as lenses do not need recoating like mirrors do. Additionally, the optical tube assembly of a refractor generally does not depend upon collimation. Lens is placed into the tube and usually does not get misaligned, unless it is dag up to some major trauma. | As the refractor is a closed-tube assembly, it may demand a longer amount of time to cool to ambient temperature. Presently used thin-walled aluminum tubes have decreased this period significantly, but cool-down time still should be accept into account. |
| Advantages | Disadvantages |
| These reflecting telescopes does not ached any chromatic aberration. Included mirrors bear only one optical surface, whereas an apochromatic lens has between four and eight causing it less expensive to develop. | Secondary mirror forms what is called a " central obstruction. " which leads to unnatural distribution of light and loss of contrast in the image. In case to resolve this problem, a few manufacturers have prepared so- called planetary Newtonians, having smaller central obstructions ( some as small as 16% of the aperture ). |