spotlight Newton I use mainly a concave primary mirror that focuses light beam forward , just before the fire There is a place second mirror (piano) , inclined 45 degrees which deflects the optical beam at the side of the support tube is where you put the focuser. In order to avoid the presence of spherical aberration is necessary that the curvature of primary mirror has section parabolic and spherical .
The secondary mirror is maintained along the optical beam by a ray structure called in slang " cruise" or " spider (spider) which must be the least intrusive as not to cause diffuse light.
The greatest honor of Newton telescope is simple design that has greatly contributed to its spread is that the realization of large diameters for amateur equipment. The Newton telescopes are suitable for any type of observation, their "inclination" towards a category of objects over others depends on the relative openness that if pushed (f / 7 and beyond) makes them excellent for observations of objects in the solar system because of low obstruction (caused by the secondary mirror) and if forced (f/4...6) makes them very practical for photography of deep sky objects.
The main drawback of the Newtonian is the presence of coma (aberration extra-axial), which can reach nuisance levels in individuals at short-focus (however partially remedied by adopting a set of corrective lenses along the optical path), as well as the dimensions of the specimens of significant opening. Do not underestimate the negative effect of convection due to the open tube that may cause a slight deterioration of the image quality.
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