Steel TUBE (QUATTRO 250 ST):
Fast focal ratio of f/4.
Black Diamond P250/F1000 Reflector. This is especially important for astro-photographers dealing with long exposure times. Imaging telescopes made of less thermally stable material can deviate from optimum focus after long time exposures. It can remain in focus for a longer period of time and long exposure images will stay clear and in focus.
It comes with a impressive 0.5 mm Ultra-Thin Secondary Mirror Supports and it offers 56% more Light-Gathering than the 200mm.