Leander McCormick Observatory
McCormick 26-inch Refractor Specs

General System Data: Fraunhofer Refractor

Manufacturers : Alvan Clark and sons
Effective focal ratio : f/14.857
Effective focal length : 391 inches

(1) Crown Glass
    Outer Diameter : 27.2 inches
    Clear Aperture : 26.25 inches
    Curvature radius 1 : 161.39 inches
    Curvature radius 2 : -161.39 inches
    Refractive index at 588 nm : 1.517
    Thickness (central) : 1.884 inches
    Weight : 70 pounds
(2) Flint Glass
    Outer Diameter : 27.17 inches
    Clear Aperture : 26.25 inches
    Curvature radius 1 : -162.07 inches
    Curvature radius 2 : -21140 inches
    Refractive index at 588 nm : 1.628
    Thickness (central) : 0.958 inches
    Weight : 110 pounds
(3) Focal Plane
    Field Diameter : 5.1 inches (with plates)
    Angular Field : 0.75 degrees (with plates)
    Plate Scale : 20.75 arcsec/mm