BBC Sky at Night Magazine
Much thought has been put into the optical system on the 20032PNT, using a 200mm, f/3.8 paraboloid primary mirror and a short-axis 90mm plane secondary mirror. The primary mirror is made of PZ33 which is very similar to Pyrex, then primary and secondary mirrors are coated in a reinforced aluminium coating which helps to give high reflectivity. This all leads to a very fast f/3.2 system that holds collimation very well during temperature changes or general moving around. Included with the telescope is an air-spaced quartette coma corrector/reducer that is screwed into the focuser. The reducing side is 0.8x, taking the focal length of the scope from 760mm to 640mm and making full-frame photography achievable and with excellent perimeter dimming control there is minimal vignetting. To collimate the telescope, the top of the focuser is unscrewed and the coma corrector has to be removed. There is an eyepiece holder included that can then be attached, allowing a collimating device to be inserted that makes the collimation process simple.