Orion 05531 Thin Off-Axis Guider for Astrophotography (Black) Delightfully thin off-axis guider ideal for use with Newtonian reflector telescopes and DSLR cameras Lets you guide and capture astrophotos simultaneously through one telescope. No guide scope required! 10.5mm thickness perfect for use with Newtonian reflectors which have limited back focus travel Will not interfere with the use of coma correctors thanks to its thin profile Compensates for any existing flexures that may interfere with accurate guiding and tracking