Monocular

I was asked by the Exploratorium to design a minimalist telescope that might be used in the new building (the Exploratorium is moving from the Palace of Fine Arts to Pier 15) . This was my first attempt, an open framed 3.5x Galilean telescope. I attached the focusing screw to the objective lens not the eye piece (which is typical) to further simplify the design. Galilean telescopes have the advantage of producing an upright image with only 2 lenses but suffer from high distortion above 3x.

Looking through the scope, the spherical distortion and chromatic aberrations are notable, especially if the scope is poorly focused. I ended up using 1/4''-20 threaded rod for the focus adjuster, this was way too fine for accurate focus control as it was hard to tell if you were getting more or less focused in less then 5 or 10 turns of the knob.

Given the image quality problems with the Galilean scope I made this "looks like" model for a monocular using Keplerean optics using 8020 aluminum stock and laser cut cardboard. A Kepler style scope produces a clear but inverted image, so the model included a pentagonal case that was scaled to hold erecting prisms to un-invert the image. To solve the slow focus problem I modeled a transverse focus knob like a microscope capable of moving the objective lens quickly but precisely.