1-1/4" 20mm plössl eyepiece from starfinder lenses

Turn the (Celestron, Orion, Sky-watcher) finderscope sleeping in your closet into a ~20mm plossl eyepiece 1-¼". Just make sure you see a reflective greenish tint on the lenses or the eyepiece will suffer from reflections.

• First you should blacken the edges of the lenses with a permanent sharpie to increase contrast by canceling edges reflexions
• Then slide them into the eyepiece body (corps.stl) in the same order and orientation they were into the starfinder screwable eyepiece (flat faces must point outward on both side)
• Then screw the lock (lock.stl)
• Then screw the skirt (jupe.stl)
• Finally plug the TPU bonnet from the top

A field stop is integrated to the skirt and sharp to the eye as can be seen on the photo. It should also act as a baffle. 

Eye relief is small so if you wear glasses you will not be able to see the full field of view.

I also tried to build a double plossl from two starfinders but eye relief is even smaller and you nearly have to insert the eyepiece in your eye to see the full field of view.

I find the performances quite good through all the field of view but degrades a lot near the outer diameter.

With this eyepiece you should be able to distinguish the Saturn ring's in a small scope:

• With a cheap achromatic refractor Ø80mm f/5 the magnification will be 20x with only the eyepiece, 40x with a 2x barlow lens, and even 80x with an extension tube between the barlow and the eyepiece.
• With an apochromatic refractor Ø80mm f/7.5 the magnification will be 30x with only the eyepiece, 60x with a 2x barlow lens, and even 120x with an extension tube between the barlow and the eyepiece.

I may add an 1-¼" adapter to put the eyepiece back on the starfinder scope.