This apochromatic 2.7x Barlow lens with genuine ED glass for correcting off-axis coma in Newtonian telescopes can be combined with a second APM 2.7x Barlow. Mounted at a specific distance from each other, the magnification increases to 6.25x. Of course, coma correction and image flattening are retained.
A single Barlow element provides a magnification factor of 2.7x and a fully illuminated image field of 26 millimetres with a back focus of 105 mm (measured from the centre of the last lens). It is optimised for f/4 Newtonian telescopes and simultaneously corrects coma in these telescopes. Dobsonian owners in particular will benefit from this, as they can enjoy a coma-free view of celestial objects as they drift across the field of view.
For the 6.25x configuration, two 2.7x elements are simply connected to each other via an extension sleeve. This configuration results in a corrected field of view of 14 millimetres in diameter at a distance of 84 millimetres (measured from the centre of the last lens).
The double Barlow allows high magnifications for planetary photography with Newtonian telescopes at an aperture ratio that also allows high frame rates. To do this, the camera sensor only needs to be mounted 84 millimetres behind the centre of the last lens.
The design of each individual Barlow element features a group of two lenses made of Chinese ED glass FK61 (comparable to Ohara FPL51). The lenses are cemented and coated on both sides with a broadband multi-coating, which has a transmission of over 99% in the spectrum from 400 nm to 700 nm.
Scope of delivery:
- Two 1.25" ED Barlow elements with 28.4 mm filter thread
- extension tube
