The Stellarvue SV90TF 90mm Telescopes are their most advanced 90 mm apo triplet telescopes. The Stellarvue Telescope SV90 TF features Stellarvue 's exclusive Calcium Fluorite 90mm f-7 (630 mm focal length) objective lens. This is a top rated visual and photographic instrument, as the many images posted on their site can attest to. The 3" Feather Touch focuser on this Stellarvue Telescope is larger than needed in providing wide field large chip imaging. Their proprietary, hand figured, calcium fluorite lens has received top ratings for its optical prowess. The six hand figured telescope ED lenses have several extreme broadband coatings, giving high contrast for the most vivid stars and the darkest of skies. These coatings transmit light above and below the visual spectrum, which is important to minimize reflections seen on ccd images. The 3inch feather fosucser offers 3.5" of travel and is large enough to work with our biggest field flattener. So this focuser is perfect for visual and imaging use with all ccd cameras on the market. The feather touch features an ultra-smooth coarse/fine focus knobs (10:1 Ratio), internal brake system, ultra-low backlash system and may be fully rotated. Don't compromise on a telescope, get the best.