| This unique off-axis guider body is designed for 35mm imaging. A knurled slip ring attaches it directly to the 2"-18 thread rear cell of all Celestron 5" through 14" Schmidt-Cassegrains and all Meade 8" to 16" Schmidt-Cassegrains and Ritchey-Chrétiens. It has a knurled slip ring that allows 360° rotation of the guider body for camera orientation. Once the slip ring is tightened to hold the camera at the desired angle to frame the photographic subject properly, the guider’s unique design then allows the guiding eyepiece to rotate through a 135° arc around the periphery of the image to find a guide star and to be locked in place without disturbing the camera orientation. The telescope focuser knob may interfere in some guider orientations. The guider also has a unique radial adjustment that provides a much larger area of sky from which to choose a guide star than is possible with conventional guiders. Instead of physically moving the prism fore and aft along the guider body to move it into the light cone to locate a guide star as with other guiders (a finicky procedure that involves loosening two screws and coarsely moving the eyepiece holder by hand), the radial guider has a micrometric turn screw that tilts the prism to slowly sweep across the field of view without moving the eyepiece holder. Tilting the prism instead of physically moving it into the light cone minimizes prism shadowing on the film and offers more precise control when positioning the crosshairs of an optional guiding eyepiece. In addition, the prism is quite small, to further minimize prism shadowing on the 35mm negative. The Radial Guider’s unique tilting prism allows the guiding eyepiece to look towards the center of the image, where the potential guide stars are bright and more sharply focused. This is in contrast to non-movable prism designs, which look strictly at the periphery of the SCT image where field curvature throws guide stars out of focus and effectively dims them. The very compact guider body length is designed to minimize vignetting with f/10 telescope and f/6.3 reducer/corrector lens combinations compared with physically-longer conventional guiders, although some minor vignetting of the extreme corners of a 35mm negative may be visible. The Radial Guider needs an optional T-ring to fit your particular 35mm camera for 35mm imaging and a 1.25" illuminated reticle eyepiece or CCD autoguider for guiding long exposure deep space photos.
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