Telescope

thingiverse

The maker uses the telescope.scad file to print parts, order lenses from Edmund Optics, and assemble a working telescope. The maker edits the telescope.scad file to enter characteristics of optics like objective lens diameter, focal length, and thickness, as well as eyepiece lens diameter, focal length, and thickness. OpenSCAD generates STL files for the telescope using those dimensions. To ensure all parts are consistent, the same program is used to generate STL files for all parts. The maker sets print phase to each value in turn, renders the model, and exports each part to a separate STL file. The parts are then printed, and with purchased optics, assembled into a working telescope. A 33x223 PCX lens was used for the objective, and a 17x-50 DCV lens was used for the eyepiece. Lenses are specified by diameter in millimeters, an "x," and their focal length in millimeters. For a Galilean telescope, the eyepiece lens has a negative focal length. Magnification can be calculated from the objective lens's focal length divided by the eyepiece lens's focal length, ignoring the sign. The above lenses yield a magnification of about 4x. Edmund Optics recommends the 42x290 PCX lens for the objective (catalog number 20-565) and the 12.5x-50 DCV lens for the eyepiece (catalog number 95-474). These lenses are located in the clearance products area of their website. It's recommended to order lenses first and wait to print parts until exact dimensions can be determined. For clearance lenses, dimensions may be slightly off listed values, so measure them when received and put those dimensions into OpenSCAD. OpenSCAD models can be completely parametric, allowing you to choose other lenses for different telescopes. You can increase the diameter of the objective lens to increase the field of view.