Telescope Eyepieces, 26mm & 28mm, 1.25" dia.
Description
This project was inspired by Jerry Oltion's article in the September 2020 issue of Sky & Telescope, p. 74. These are two eyepieces for an astronomical telescope made from lens sets available from Surplus Shed (surplusshed.com). These are based on the following items: L3973 Modified Plössl, 26mm fl L3820 Modified Plössl, 28mm fl Each set consists of three lenses (eye, middle, field) between 33mm and 35.5mm in diameter. I've posted more eyepiece designs here: https://www.thingiverse.com/thing:4580598 https://www.thingiverse.com/thing:4597001 Each eyepiece consists of the following parts: 1) 1.25" barrel with a 42.6mm dia. 1.5mm pitch external thread, 2) Housing with a matching internal thread, 3) Three lens spacers, one each for the eye lens, middle lens, and field lens. 4) Flexible eye guard. I made these from ABS except for the flexible eye guards. ABS is more durable, lighter, and has a less glossy finish than PLA. The eye guards are printed from black TPU The vertical resolution of the print is important to get acceptable quality on the threads. I printed mine at 0.12mm vertical resolution and a speed of 20mm/s. You can print all the parts without supports, but some files may need to be flipped 180º when slicing. I haven't yet used these eyepieces under the night sky. I have compared my previous design (https://www.thingiverse.com/thing:4580598) with a commercial 26mm Super Plössl from Meade. The 3D printed eyepiece compares very favorably to the commercial eyepiece. There's a little more distortion at the edges, and some chromatic aberration. A view of the moon shows color fringes, whereas the Meade eyepiece is color-free. Contrast is as good or better than the Meade lens, and I notice no internal reflections.
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