: Community forums such as Cloudy Nights are excellent places to find advice from other builders who have used the book and may share resources or design spreadsheets.
After the glass is close to its final shape, the polishing stage begins.
If you're looking for new and improved designs, consider the following:
: Provides a comprehensive summary of the book's hands-on approach. Open Library making a refractor telescope norman remer pdf 12 new
An achromatic lens must combat —the tendency of a single glass lens to act like a prism and focus different colors of light at different points. Remer teaches makers how to combine two matching types of optical glass:
Detailed guides on using the Foucault test, Ronchi test, and star testing to check the precision of your lenses.
Detailed methods for testing the lens's accuracy and making corrections. : Community forums such as Cloudy Nights are
: Remer emphasizes that making a refractor is not "too difficult" for those familiar with basic tool work, despite common misconceptions in the amateur community. Purchasing Options
: Remember that managing four surfaces takes roughly four times the processing time of a standard Newtonian mirror—but the resulting contrast is unparalleled.
: He provides step-by-step coaching on using rudimentary tools and common abrasives to grind the glass into the correct spherical shape. Open Library An achromatic lens must combat —the
Optical schematics and interference patterns require close inspection. Digital PDFs allow builders to zoom in closely on line drawings and mathematical formulas without losing resolution.
Raw measurement is only the first step; the real magic happens in the testing phase. After polishing, the lens is installed in a temporary cell and mounted in a test rig to be pointed at an artificial star (a pinhole with a bright light behind it) or a real celestial target. Using a high-power eyepiece and a Ronchi screen or a knife-edge tester, the builder examines the star's diffraction pattern. This test reveals whether the lens is suffering from spherical aberration and zone errors. Based on the pattern, the builder returns to the polishing bench to apply targeted correction—altering the stroke pattern—a process known as "figuring." This iterative loop of test, analyze, and correct continues until the lens produces a textbook-perfect star test.