I've seen the description "Meade #128 3 x Telenegative Barlow Lens" and similar a few times now. I understand what a 3x Barlow is but what is a " Telenegative Barlow" ?
So if I am getting your drift, a negative lens, lengthens the focal length. Which suggests that all Barlow attachments should be call "Telenegative Barlow" so is "Barlow" simply an accepted commonly used shortening?
that is correct roger
if you can imagine a positive lens (convex) converging the light rays "prematurely" before they would without the lens, then you have "shortened" the path of light, thus reducing the (focal) length (a reducer)
the exact opposite for a "negative" (concave) system (a barlow) which "splays" the light further on from its normal path making the convergence point longer
thus it seems strange terminology to use "negative" and "amplifier" in the same sentence...... but there you go ha ha! it is correct!
pat
