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What is an Off-Axis Newt?


An Off-Axis Newtonian is a reflecting telescope that by design deflects the primary mirror’s reflected light slightly out of the incoming lightpath accomplishing a reflecting type instrument with no central obstruction. This type of specialized mirror is usually manufactured by first grinding, polishing, and parabolizing a larger “Parent Mirror”. The “Parent Mirror” is then cut into four smaller off-axis paraboloids (OAP). As an example, the OA-4 F/10 starts out as a 10-inch F4 “Parent Mirror” and ends up as (4) four-inch F/10 OAP`s.  It is this design which provides an unobstructed reflector without requiring a tilted primary mirror.