From magnification to letting in enough light at night, here's how to choose the perfect monocular for stargazing and astronomy.

lens 38 mm in diameter with a 50 mm focal length. Add a printed enclosure, and the result is a monocular night vision display. Do it three more times and arrange them around one’s eyeballs ...

One lens emits the IR illumination beam and contains the CMOS sensor. The other lens focuses the image for the oversized digital viewfinder. Unlike most night-vision units, which have eyepieces ...