Dobsonian Telescopes and Amateur Astronomy

March 03, 2014

Dobsonian1200 (2)


Photographer: John Stetson
Summary Author: John Stetson

My daughter, Katy, is shown here observing the Sun on the horizon through a home-made Dobsonian solar scope near Sebago Lake, Maine. John Dobson, "the Thoreau of the Skies," taught amateurs how to make telescopes for over five decades. He died earlier this year. Dobson built this scope in 1999 while traveling though Maine. On that visit he also supervised the construction of several primary mirrors and telescopes at the Maine Youth Center, a juvenile correctional facility that's now closed.

According to astronomer and popular science writer Timothy Ferris in his book "Seeing in the Dark," the revolution in amateur astronomy has been a result of three things: the Dobsonian telescope, charge-coupled device (CCD cameras), and the internet.  The Dobsonian telescope revolutionized amateur astronomy because it could be made inexpensively; CCD cameras because of their sensitivity; and the internet because it allowed the sharing of images and ideas.

This particular scope was made with:

  • An old vinyl record and three teflon pads (to provide movement in azimuth)
  • A sonotube
  • A one-way reflecting mirror for the secondary mirror
  • Green dishes purchased at a Goodwill Industries store
  • The center of a toilet paper roll (just over 1.25 in or 3 cm in diameter) to receive a standard eyepiece
  • A 6 in (15 cm) pyrex mirror (after many hours of rough grinding, fine grinding, polishing, and figuring)
  • A wooden rocker box made of scrap plywood

The bottom photo illustrates an assortment of what my daughter, my students and I saw over the course of several years in which we used the solar scope to make sunspot drawings. Always use extreme caution when looking toward the Sun. Photos taken on September 21, 1999.