Here are a few simple adjustable scopes that I've made. Each scope only requires 1 concave lens (25mm, 38mm, or 50mm) for the eyepiece, and 1 convex lens (50mm or 75mm) for the objective. Magnification will typically range from 1.5x–10x depending on the focal length of your lenses. I included a few helpful files for determining the correct focal length and distance between lenses needed to get a desired magnification.

The basic assembly is as follows:

1.) [25mm→50mm Scope]

25mm Parfocal Extension (optional) → 25mm Eyepiece+Arm → 50mm Objective → 75mm Adapter (optional)

2.) [38→50mm Scope]

38mm Parfocal Extension (optional) → 38mm Eyepiece+Arm → 50mm Objective → 75mm Adapter (optional)

3.) [50→75mm Scope]

50mm Eyepiece → 50mm Arm → 75mm Objective

**Notes

–The parfocal extension is only necessary for higher magnification which require a greater distance between your eyepiece and objective lens.

–I made the 50mm Eyepiece and 50mm Arm models separate to make it easier to print.

–Higher magnifications will show a greater amount of spherical aberration (unless you use achromatic lenses)

–It's best to use a very powerful concave lens (i.e. Focal Length = -5cm or smaller). This will allow you to more easily achieve higher magnification at a shorter distance.

–Your convex lens will most likely need to have a focal length between 10cm and 20cm.

Let me know if you have any question!