Telescope Eyepieces, 7mm, 32mm, 45mm, 52mm, 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 four eyepieces for an astronomical telescope made from lens sets available from Surplus Shed (surplusshed.com). These are based on the following items: L3721 Reverse Kellner, 52mm fl L3715 Erfle, 32mm fl L3713 Reverse Kellner, 45mm fl L1646 Reverse Kellner, 7mm fl Each set consists of two or three lenses (eye, middle, field) ranging from 8mm to 36mm in diameter. I've posted more eyepiece designs here: https://www.thingiverse.com/thing:4580598 https://www.thingiverse.com/thing:4587751 Each eyepiece consists of the following parts: 1) 1.25" barrel with a 1.5mm pitch external thread, 2) Housing with a matching internal thread, 3) Two or three lens spacers, one each for the eye lens, middle lens (if used), 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 need to be flipped 180º when slicing. I have compared these eyepieces with commercial eyepieces from Meade. The 3D printed eyepieces compare very favorably. There's a little distortion at the edges, and some chromatic aberration. A view of the moon shows color fringes on some of these designs, whereas the Meade eyepieces are color-free. The FOV of the 7mm eyepiece is very narrow. Contrast is as good or better than the Meade lenses, and I notice no internal reflections.
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