TeleVue - Barlows

Properly designed Barlows do wonderful things: They amplify power, slow the
telescope's f/# (improving eyepiece sharpness), and give designers the
opportunity to compensate for eyepiece aberrations.

Tele Vue Barlows use multi-coated high index glasses for optimum
aberration correction, exceptional contrast with virtually no light loss.
Observed performance is aberration free, even when tested with f/4 scopes.
They even improve our competitor's eyepieces and telescopes!

Powermate™ vs. Barlow

To understand the Powermate, we must first understand the Barlow lens.
Barlows amplify the power of a telescope. They can be considered "focal
reducers" for eyepieces, or "focal extenders" for objectives. Terence
Dickenson, in his Barlow test report in Sky and Telescope, July 1997, says:
"Technology has erased the old objections. A modern Barlow will not degrade
your telescope's optics. Anyone telling you otherwise is using outdated
information.

Moreover, the highly regarded Nagler eyepieces and their clones have
built-in Barlows, ample evidence that the lens is not some detrimental
intruder." Thanks, Terence, for laying the myth of the degrading Barlow to
rest.