Tag Archives: optics

Geometrical Optics and the Hastings-Byrne Refractor: Part III

by John Church In the March and April issues I reviewed the relatively simple equations that allow a lens designer to specify the total curvatures of both elements of a two-element (crown and flint) achromatic refractor objective, and how our … Continue reading

Posted in June 2012, Sidereal Times | Tagged , , | Leave a comment

Geometrical Optics and the Hastings-Byrne Refractor: Part II

John Church Last month I reviewed the “lens-maker’s formula” that allows one to calculate the focal length (the inverse of the “power”) of a thin lens, provided that one knows the refractive index of the glass and the radii of … Continue reading

Posted in April 2012 | Tagged , , , , | 1 Comment

Geometrical Optics and the Hastings-Byrne Refractor

By John Church Some years ago I analyzed the objective lens of the AAAP’s historic 6-1/4-inch Hastings-Byrne (H-B) refractor and published the results in Sky & Telescope magazine, along with a history of the telescope1. The readers of Sidereal Times … Continue reading

Posted in March 2012, Sidereal Times | Tagged , , , | Leave a comment