Ultra cheap low quality 5x expander

Found this at the dollar general near me. It's a pair of 5x30 binoculars for $5.

They're lightweight, small, and the part that you look into is easy to shoot a laser through and they actually seem to expand the beam right.Not bad for the money.

Have you tried this with a 445nm laser? I would assume that it will just melt the lenses, but if you have a low power laser, I suppose it could work.

Many of us have used cheap binoculars or monoculars as expanders. It works okay, but you lose about 40% of the power.

Cyparagon said:

Many of us have used cheap binoculars or monoculars as expanders. It works okay, but you lose about 40% of the power.

Click to expand...

They work with 405nm and I've found alot binoculars of decent quality and telescopes dont since they have an anti UV and near UV coating.

Generally any piece of glass will loose about 10%, unless it has special wavelength tuned anti-reflection coating. If you use optics with many elements, the loses will stack. Binoculars have at least 4 pieces, and 2 prisms. It is better to remove optics from the laser, remove eye-piece from the telescope, and use only the 'objective' part of the telescope laser. But then you need to match the focal lengths, which is not so simple. In general diode lasers can be coupled nicely with photographic lens. But those especially have a lot of elements.