Spotter Scope, 80mm f/5

thingiverse

This is a remix of my 80mm diameter, 400mm focal length telescope (https://www.thingiverse.com/thing:5212087), inspired by Jerry Oltion's article in the November 2021 issue of Sky & Telescope. The telescope is designed around two parts available from www.surplusshed.com: L2196 MTD 80MM DIA ACHROMATIC OBJECTIVE, 400MM FL COATED ($42) L3630 INEXPENSIVE 1-1/4" FOCUSER FOR 80MM REFRACTORS ($17.95) This version is shortened by about 90mm to accommodate a 45º diagonal: https://www.aliexpress.us/item/2251832677884206.html ($18) This diagonal provides an erect, non-reversed image. I use it with a 32mm eyepiece, which you can find here: https://www.thingiverse.com/thing:4597001 This design also includes an integrated Vixen-style dovetail. Construction notes: I printed the OTA parts in white PLA, then primed the interiors and the baffle surfaces with white primer, followed by a coat of flat black paint. The primer is necessary to keep the black paint from wicking through to the outside of the print. Be sure to mask off the glue surfaces between the segments. The segments are assembled with 5-minute epoxy. The focuser is attached with three #4 x 3/8" wood screws and washers. The objective lens is also attached with three #4 x 3/8" screws, but you will need to drill two additional holes in the objective housing. Be careful where you drill—you don't want to drill into the lens! The screws in the objective needed to be ground down so as not to intrude into the aperture of the objective. In the S&T article Jerry recommends shortening the focuser tube to avoid vignetting. I removed about 1-1/4" and printed a trim piece for the cut end. NOTE: This is the second scope I've made with the 80mm objective from Surplus Shed. In both cases, the lens was mounted backwards in the mounting cell. The double-convex element faces outward, and the plano-concave element toward the eyepiece. I unscrewed the retainer, reversed the lens, and reinstalled the retainer. If you have to do this make sure you align the marks on the edges of the two elements.