It is hard to imagine a time before the Barlow lens, but prior to 1833 that is the world our poor antecedents would have lived in! It is hard to imagine a more benevolent telescopic accessory, for its deployment bestows not one, but two valuable benefits. Its singular effect, that of extending a telescope’s focal length, belies the double-edge reward it delivers. The (perceived) extension of focal length means an increase of focal ratio, reducing any inherent ‘weaknesses’ in the main optical system. Additionally, by virtue of changing the telescope’s focal length, the incumbent set of eyepieces now magically produce a new range of magnifications, at a stroke doubling your choice of powers and corresponding fields of view.
This Barlow offers a fairly ambitious amplification of 5×, perhaps a challenging stress on the competency of any telescope, but it does this with a well-corrected four-element design that ensures it performs its job of bending light without detrimental contributions of its own. In common with all Barlows, it also enables lower power eyepieces to provide high magnifications that might otherwise require squinting through the tinier eye lenses of shorter focal length eyepieces.
This Barlow lens also features an eyepiece-friendly brass compression ring clamp, an easy grip rubberised barrel and a 1.25-inch filter thread.
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