Hi All,
Always wondered about those K-mart Kids science 7x50 binoculars with ruby lens, selling for $15, with the true aperture stopped down to about 22cm from 50cm. Works OK during the day, but the view is dim for night astronomical use.
In Cloudy Nights, someone mentioned these cheap ruby lens binoculars are not achromats, having no clown and flint elements on the objective lens:
http://www.cloudynights.com/topic/50...nses-the-norm/
Someone posted on Youtube, ie, bought the same type of binoculars in the US and pulled the objective lens out, confirming there is no crown, no flint, ie, not an achromat but a thick single glass objective:
https://www.youtube.com/watch?v=4xTIjG7yJOM
Not that bad with all that glass, ie, 6 glass lens and 4 glass triangle prisms in a plastic housing and metal screws for $15 brand new, provided you choose a pair where the ruby coating is not so thick that cast a really bluish green image to everything you see.
Enjoy!
Kind regards,
Bill
