Meade #777 Off-Axis GuiderThe #777 Off-Axis Guider (OAG) permits use of a CCD Autoguider or guiding by an astrophotographer during long exposure astrophotograpy or imaging. Considered a "must have" item by many astrophotographers. Requires use of an illuminated reticle eyepiece if guiding "by eye", not included. The OAG couples the camera or imager body to the telescope and diverts a small part of the light at the edge of the telescopic field of view to an illuminated reticle guiding eyepiece or a CCD Autoguider mounted at 90° to the imaging camera. This small star field is then observed by the photographer or Autoguider to detect any change of position in a selected guide star, with continual small corrections being made to the telescopes drive based on close observation of the stars movement. Mounting an SLR camera to the OAG may require use of an appropriate T-Mount for that model camera.