TASCO 49060700 60x700mm Spacestation Refractor So, my grandfather so graciously gave me his TASCO 49060700 60x700mm Spacestation Refractor Telescope, which is extremely wondrous. Any way, I found this answer to my 3x barlow lens, which I believe is saying multiply the magnification on the lens to the barlow. I've got three separate lenses; 25mm, 10mm, and a 4mm. My question is, do I multiply 25 by three(25 being the 25mm) and I get 75x magnification?
A telescope's magnification is its objective focal length divided by the eyepiece focal length:
$$ \frac{700~\text{mm}}{25~\text{mm}} = 28 $$
A Barlow lens multiplies the effective focal length of the objective:
$$ \frac{3 \times 700~\text{mm}}{25~\text{mm}} = 84 $$
The 10 mm eyepiece gives 70x magnification without the Barlow.
Other configurations exceed the maximum useful magnification of 2x per mm of objective diameter (60 mm → 120x).