How does focusing work with the HyperStar system?
Many CCD imagers install accessory Crayford-style focusers at the rear of their SCTs for accurate focusing without mirror shift when placing a CCD at the back of the telescope. When the CCD is mounted at the front of the telescope using the HyperStar lens, focusing must be accomplished by moving the primary mirror (by turning the original focus knob). We recommend the use of the Starlight Instruments Feathertouch SCT MicroFocuser in place of the standard focus knob. For manual focusing, the 10:1 fine focus ratio is ideal. For robotic focus with higher precision, the optional MicroTouch focus drive allows for remote (wireless) focusing with digital readout as well as autofocusing capabilities and more. (Availability of MicroTouch motor focus: December 2003.) Mirror shift is less of a concern at the front of the scope. With the secondary mirror removed, the amplifying effect of the secondary is eliminated, so mirror shift is approximately 5 times less than at the back of the telescope. W
