Optical paths

To use one optical train to provide two separate optical paths, an aperture plate must be placed over the telescope main aperture to redefine how light enters the optics. I placed a 5" circular aluminum plate over the main aperture, and this plate had two circular cutouts (sub apertures), each 1.5 inches (37 mm) in diameter. The initial 5" f/10 system had a focal length of 50 inches, about 1.25 meters. My two sub apertures thus formed two 1.5" f/33 optical paths. This sub aperture system is quite comparable to Galileo's telescopes, which had similar apertures and focal lengths.

I initially used a diverging/converging lens pair just prior to the camera to allow an alternate focussing option, but I later switched to a converging lens only. Here are some primitive drawings of the optical system. Light flows from left to right.

My friend Wayne Welch generously created these visualizations from hand sketches I sent him:

Here is the detector stack (version 2) with a ZWO CMOS camera, a pellicle, alignment LED (hidden on the underside of the pellicle cube), and a short tube holding the converging lens.

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