Barlow Lens

One very useful lens every amateur astronomer really should have is a Barlow Lens.Probably its greatest value is that it effectively doubles the number of eyepieces at your disposal.

The lens is inserted between the focuser and the eyepiece in a reflector telescope and usually between the diagonal and the eyepiece in the refractor.

With many telescopes it can also be inserted between the focuser and diagonal, and in this position gives greater magnification.

As well as increased magnification it also helps with eye relief and reduced aberration in the eyepiece.

It is for this reason that a Barlow plus a lens very often outperforms a single lens producing the same magnification.

As the magnification of a telescope is equal to the focal length of the scope divided by the focal length of the eyepiece, the addition of a 2x and 3x Barlow lens increases the magnification accordingly.

Just ensure you select one with a barrel size that will fit the eyepieces you are going to use it with, this will typically be 1-1/4 inches or 2 inches.

Orion Shorty 1.25" Barlow
For approximately the same cost as a single telescope eyepiece, this handy accessory essentially doubles the quantity of eyepieces at your fingertips.

2x ED Barlow Lens
If you're looking for an affordable way to achieve high-power viewing of the moon and planets, double stars and even close-up views of terrestrial subjects, a Barlow lens is the way to go.

Here is an interesting buyers guide to Barlow Lenses....

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