For a STEM project I wouldn't be fussy about image quality. Doesn't hurt to show kids what's poor, vs what's good (binoculars will do). The really clever kids will start to figure out why the image isn't so great, and what separates the crap from really good optics. And they'll learn something about optics, in the process, which might captivate them.
The first scope I assembled as a kid started with a simple magnifying glass for the objective. You can guess how awful that was, but it did work, even at 5X. But the next attempt I mated a 135mm camera telephoto lens to a 20mm Erfle, and at the time that was something pretty nice.
Next came a 50mm finderscope someone gave me.
Then came the scope that got me hooked - discovering the pieces of a beautiful 1880 Cooke 4.5" refractor scattered in the science labs at school, followed by a year refurbishing it and setting this up (with help from the school). The sight of Saturn in that scope was simply jaw-dropping.
This might be why I'm now really, really, picky about image quality...
Edited by luxo II, 01 March 2021 - 08:08 PM.