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Tele Vue 2" 2X Big Barlow Lens
At the left is a 2" 2X Barlow Lens that will help enable a
complete space-walk using only 4 eyepieces and an additional 2" 4X Powermate from Tele Vue.
This 2X Barlow works to double the magnification of the 55mm Plossl, the 41mm Panoptic,
and the 7mm Nagler Type 6 eypieces closest to the table values. This will cover the
27mm, 20mm, and 3.4mm table positions in addition to the values of these eyepieces when used
alone. The 5mm Nagler Type 6 eyepiece will always be used alone.
Most good Barlow lenses are 2 element negative lenses that
double the telescope's Objective lens' focal length, - effectively halving the eyepiece's
focal length. Tele Vue's "Powermate" lenses are 4 element modified Barlow lenses that
restore the location of the eyepiece's exit pupil after effectively halving the eyepiece's
focal length. Normal Barlow lenses leave the eyepiece's exit pupil in the position it was
moved to during the focal length change.
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