Baader Planetarium Glasspathcorrector 2" / 1.7x for Newtons

Its primary purpose is to allow Newtonian telescope owners to use binoviewers. It solves the two main barriers to this: it extends the focal path by 1.7x so you can reach focus, and it corrects the coma inherent in Newtonians, ensuring the view is sharp across the entire field.

While designed for binoviewers, it can also be used to achieve focus with other long-path accessories, such as certain cameras or off-axis guiders that may require more back focus than your Newtonian provides. However, its primary optical design is optimized for correcting the path length of a binoviewer while also correcting coma.

In a 12" f/4 Dobsonian, this corrector will make your telescope operate at f/6.8 (4 x 1.7). This has two main benefits: first, it will allow your binoviewer to reach focus, which is nearly impossible at f/4. Second, it will deliver sharply focused, point-like stars to the edge of the field, correcting the significant coma that is prominent in an f/4 system.

Yes, this corrector is designed to work with virtually any binoviewer that has a 2" nosepiece or can be adapted to one. Its function is to modify the telescope's light path before it enters the binoviewer, making it broadly compatible.

When observing a large object like the Pleiades (M45), you are using a wide field of view where stars fill the eyepiece from edge to edge. Without coma correction, stars at the periphery would appear as blurred seagulls, ruining the immersive "spacewalk" effect that binoviewers provide. This corrector ensures every star in the cluster remains a pinpoint, preserving the aesthetic of the view.

No, it is designed with a standard 2" barrel and is meant to be inserted directly into your telescope's 2" focuser. Your binoviewer would then be inserted into the corrector.