High powers are useful for detecting faint stars, use up to 50X or 75X per inch if seeing conditions permit. X Focal Ratio: f/ = Focal Length: mm. Aperture: mm. Focal Ratio Calculator. f/ Please select one of 458 telescopes from the drop-down box, or use Manual mode to enter the aperture and focal length by … Tele Vue Optics, founded in 1977, has been thrilling amateur astronomers since 1979. Focal Length Calculator. Type of telescope Formula: Aperture X Focal Ratio . It is our mission. Calculate the focal length of your telescope. Power The power of the telescope, computed as focal length of the telescope divided by the focal length of the eyepiece. Two versions of the planner … Telescope Aperture The diameter of the objective lens or mirror. It's in the materials we choose, the designs we create, the craftsmanship we demonstrate...the images … The edge support configurations have been selected after extensive discussions and represent the state-of-the-art ideas about the edge support in mirror cells for Dobsonian telescopes from a number of … Calculate the focal ratio of your telescope… Telescope Calculator ... Focal Ratio Please enter the focal ratio of your telescope. The Newtonian Telescope Design Planner uses "JavaScript" to perform the mathematical calculations; therefore, your browser must be "JavaScript" compatible and enabled. Focal Length & Ratio Useful calculators and formulae.