110mm Keplerian refractor telescope

thingiverse

I wanted to create a telescope with high light power and low magnification. This design is what I came up with for the project. I printed it with ABS plastic, so some parts have alternatives that greatly simplify ABS print dealing with warping difficulties. Some parts also come with embedded support to improve the end result versus slicer-generated support. All parts use a 1mm pitch thread with a 60-degree form of teeth. I found a 110 mm x2 magnification lens at my local optics store. Its actual focal length is 270-280mm, while it should be 250mm (4 dioptre). You can buy similar lenses online from various retailers. Unfortunately, I couldn't find lenses with less magnification (longer focal length) to create a telescope with higher image quality. However, you can use 1.25''/2'' eyepieces with the scope depending on the eyepiece holder you use. I modeled a helicoidal focuser with photo lens-like control. It has a 32mm range of focusing, with 10mm position for infinity, so eyepieces with shifted parfocality can be used as well. Since 2'' eyepieces have more deep placement of focal plane, the 2'' eyepiece holder accounts for this in the model. The scope is ready to be printed and tested. Use a standard 50/70mm dovetail model with 1/4'' thread (1/20'' pitch) for telescope holder tripods. If you already have a telescope dovetail, you can use it securing it on the body brace. You can also add a blend and lens cover. Note: Don't expect exceptional quality from this telescope since contemporary refractor telescopes have achromatic corrective lenses (flint glass) in addition to main crown glass that significantly reduces spherical and chromatic aberrations. This scope is limited to 10mm minimum eyepiece use and thus x27-28 usable magnification. Higher magnifications (lower eyepiece focal length) don't give a clear view due to spherical and chromatic aberrations (polyethylene-like view). So respect $100 telescopes that have flint glass and may give x100 and higher magnification. Update: 06/27/2017 - The 0A-eyepiece_holder_2_inch was increased by 0.2mm in internal diameter after a probe print in ABS and test with my old good 2'' eyepiece. The new version should hold the 2-inch eyepiece tightly, while the previous version didn't fit it quite well.