The Baader 2" Glasspathcorrector® 1.7x for Newtonian Telescopes is a high-performance optical accessory with a full aperture and integrated coma-corrector, designed for advanced visual observation and correction of optical path issues.
Features
- 2" Glasspathcorrector® Factor 1.7 for Newtons – at full aperture with integrated Coma-Corrector.
- Suitable to insert into the Baader MaxBright® II Binoviewer and the Mark V Giant Binoviewer (insert diameter: ∅ 2" - 50.8mm, incl. M48 filter thread).
- A Baader Glaspathcorrector® is not a Barlow lens! The reason for this name is only secondly the displacement of the focal point.
- A Glaspathcorrector® is primarily intended to correct the prismatic colour fringing that occurs on Refractors due to the high amount of glasses used in binocular prisms.
- For usage with the former MaxBright® Mark I or other binoviewers with T-2 but no Zeiss dovetail, you need additionally the T-2a Change Ring with Zeiss Dovetail (#2456320). Both parts are also available as a set: 2" Glasspathcorrector® 1.7x for Newtons incl. T-2 change ring (#2456301).
- Saved Optical Path: ca. 80mm.
- Includes 1x T-2 Dustcap with Zeiss-Dovetail (#2904020).
Glasspathcorrector® (GK) for Binocular Viewers and more
The 2" Glasspathcorrectors for Binocular Viewers provide full aperture compatibility for your Baader MaxBright® and the Mark V Giant Binocular Viewer!
These large Glasspathcorrectors make it possible to mount a binocular viewer on almost ANY telescope with a 2" connection. Even owners of "fast" (i.e., short focal length) refractors and photographic Newtonians can enjoy views of deep sky objects with both eyes without vignetting, reflections, or light loss.
For Newtonians with DSLR camera compatibility:
The corrector is delivered ready to connect to the Mark V Giant Binocular Viewer. To connect to the MaxBright® Binoviewer, the T-2a Change Ring with Zeiss dovetail (#2456320, €48) from the Astro T-2 System® is also required—both parts are available as a set (#2456301). Owners of Dobsonian Newtonians should ensure they have 25 mm of "backfocus" available. For Synta and GSO Newtonians, the Four-in-One Adapter (#2458190) is recommended. This adapter can be screwed directly onto the M60 thread at the base plate of the focuser, replacing the standard long 2" insert, saving up to 40 mm of optical path length.
The Glasspathcorrector® 1.7x for Newtonian reflectors reduces the optical path by approximately 80 mm, enabling focus compatibility for many Newtonian telescopes with a binocular viewer.
Baader Glasspathcorrector (GK) 1.25x/1.7x/2.6x
The Glasspathcorrectors with factors of 1.25x, 1.70x, and 2.60x shorten the optical path length. Measurements were taken using a 2" focuser on a Traveler 105mm/f6 apochromat with 35mm ED eyepieces, a giant field binocular viewer, a 90° T-2 diagonal prism, and the Glasspathcorrectors. When the lens system is placed in front of the prism, the focal length is shortened by about an additional 15 mm.
| Focal Distance (optical path length) |
Without correction |
With GK 1:1.25 |
With GK 1:1.70 |
With GK 1:2.60 |
| From the support surface at the focuser – with 90° T-2 prism |
162 mm (unfocusable) |
144 mm |
122 mm |
79 mm |
| Straight-through with 2" adapter (no prism, important for Newtonian mirrors) |
112 mm |
94 mm |
71 mm |
28 mm |
| Straight-through with T-2 Quick Changer |
123 mm |
105 mm |
82 mm |
39 mm |
These three lens systems solve focusing problems for nearly all common telescope types. The lens housing includes both a connection thread for the giant field binocular viewer and a T-2 clamping flange. This flange can be clamped at any T-2 (M42) thread connection between the positive and negative thread parts, enabling unexpected experimental possibilities (using accessories previously not usable with your telescope).
Baader Glasspathcorrector (GK) 1.25x – Example Use with Baader Safety Herschel Wedge
Glasspathcorrector® 1:2.6
For this Glasspathcorrector®, the lens housing must not be opened, as the lenses are individually centred and optimised for maximum performance as a Glasspathcorrector® (not a Barlow lens!). Only "Lens Configuration B" is available for this corrector (see the Astro T-2 System® information sheet). The 2.6x Glasspathcorrector® can be screwed directly into any T-2 diagonal prism or T-2 amici prism and installed directly in front of the giant field binocular viewer.
Additionally, as explained above, the 2.6x Glasspathcorrector® can be clamped between any T-2 thread connections at its thin flange. The flat, thin edge of the Glasspathcorrector® must always face the eyepiece, while the lens housing must face the telescope.
Connection Examples
Glasspathcorrectors with 1.25x and 1.7x Factors
For these correctors, the lenses are cemented and can be removed from the housing and installed in reverse. For all applications, the convex (outward-curved) lens side must always face the telescope (or the sky) when installed in the housing.
Binocular Viewing
Giant Field Binocular Viewer (only applies to GK 1:1.25 and GK 1:1.7)
The Glasspathcorrector® is screwed directly into the Zeiss Micro-Adapter (dovetail) on the front of the binocular viewer.
MaxBright® Binocular Viewer
All Glasspathcorrectors are installed in "Lens Configuration B" (lens housing facing away from the binocular viewer). Space or a screw thread is provided for this configuration in T-2 prisms, 1¼" sleeves, or 2" sleeves. To save optical path length, the lens part of the Glasspathcorrectors® is not inserted into the binocular viewer. The beam splitter of the binocular viewer is positioned as close as possible to the viewer's front edge.
T-2 Thread Connections
Whenever a new accessory cannot achieve focus due to insufficient focuser travel, the Baader Glasspathcorrector® may be the solution. Nearly every telescope manufacturer provides a T-2 connection for their devices. These adapters are usually very short because the T-2 thread is typically intended for attaching a 35mm camera. This is exactly where the Baader Glasspathcorrector® is installed.
Baader manufactures a wide range of eyepiece clamps, spacer rings, and adapters with T-2 threads (e.g., the universal adapter and T-2 spacer ring 40mm or 15mm length), ensuring a suitable connection can almost always be assembled.
Camera Lenses
If you have a camera lens with a T-2 thread, many "third-party lenses" (e.g., Tokina, Soligor, Vivitar, etc.) allow the bayonet ring to be removed, revealing a T-2 thread. Using the Baader Glasspathcorrector® with the T-2 sliding focusing tube or the 1¼"/T-2 eyepiece holder, you can visually use your existing 1¼" diagonal prism and generally all 1¼" eyepieces with the camera lens!
