Specification: Focal Length:250mm (Astrograph) Diameter:51mm Aperture: f/4.9 Focuser: WIFD (WO INTERNAL FOCUS DESIGN)(Compatible with EAF)Image Circle:45mm full frameTube Length:298mm Dew Shield Circumference : 265mmDew Shield Diameter :84mmWeight : 3.90lbs /1.770kg (OTA only)5.25lbs / 2.380kg (OTA withring,dovetail and saddle)