Baader Classic Ortho 18mm Eyepiece - 1.25"
- 18mm Focal Length
- 50° Apparent Field of View
- Classic 4-Element Orthoscopic Design
- 1.25" Barrel Diameter
- Engineered for Safe Solar Projection
- HT Multi-Coated Optics
Simulate the exact field of view of the Baader Classic Ortho 18mm Eyepiece - 1.25" with your specific telescope.
Launch Visual AssistantThe Baader Classic Ortho 18mm Eyepiece resurrects a legendary optical design, delivering exceptional contrast and on-axis sharpness in a modern 1.25" format. Its 50° apparent field of view is rendered by a 4-element system with only four glass-to-air surfaces, a configuration that maximizes light transmission and makes it a definitive choice for critical planetary and solar observation.
Based on the original Zeiss Jena orthoscopic eyepieces, the Baader Classic Ortho uses a simple but powerful 4-element design to achieve a view free of distortion. While the 50° apparent field is narrower than modern wide-field eyepieces, this is a deliberate trade-off to deliver the highest possible contrast and resolution at the center of the field, where planetary detail is most critical.
Baader’s HT multi-coatings are applied to all air-to-glass surfaces, and the lens edges are meticulously blackened to suppress internal reflections. The result is a transparent view with a dark background, allowing you to resolve subtle cloud bands on Jupiter and fine rille detail on the Moon without interference from scattered light.
Unlike many modern eyepieces that use UV-cured cement, the Baader Classic Ortho is constructed with a heat-resistant cement that will not degrade under the intense heat of solar projection. This eyepiece has been tested for up to six continuous hours on 150mm refractors, making it one of the few currently produced eyepieces genuinely safe for this application.
The entire body is machined from metal, with dual internal field stops designed to distribute heat effectively. This robust, no-plastic construction ensures that focused sunlight will not cause internal components to outgas or melt, preserving the optical integrity of your telescope and the eyepiece itself.
With a lean housing diameter of less than 35mm, the Classic Ortho 18mm is exceptionally adaptable. Its primary advantage is for high-magnification planetary imaging via classical eyepiece projection, where its on-axis sharpness can be leveraged to capture fine detail.
The slim profile also makes it a perfect match for binoviewers, where wider eyepieces can cause issues with nose clearance. Additionally, the long housing is ideal for securely mounting smartphone adapters for digiscoping, allowing you to easily capture and share your views of the Moon and planets.
The Baader Classic Ortho 18mm uses a classic orthoscopic design with only four lens elements. This simple, highly-corrected optical path minimizes light scatter and maximizes contrast, providing extremely sharp, high-fidelity views of planetary surfaces and other high-magnification targets where detail is paramount.
This eyepiece is built using a special heat-resistant lens cement and an all-metal construction with no plastic parts. Most modern eyepieces use UV-cured cement that can melt or separate under the focused heat of the sun, permanently damaging the eyepiece. The Baader Classic Ortho is specifically engineered to withstand these temperatures.
The Baader Classic Ortho 18mm is an excellent choice for this scenario. Its high on-axis sharpness is critical for capturing fine details like the Great Red Spot or subtle cloud bands on Jupiter. When used with an eyepiece projection adapter (like the Baader OPFA), it allows you to achieve the high magnifications necessary to bring the planet to a useful image scale on your camera's sensor.
Yes. The slim housing, with a diameter under 35mm, makes the Baader Classic Ortho 18mm an ideal candidate for binoviewers. Unlike eyepieces with wider bodies, a pair of these will easily fit side-by-side without creating issues with interpupillary distance or nose clearance, allowing for comfortable two-eyed observing.
Absolutely. The 18mm focal length provides a useful magnification for framing large sections of the Moon's surface or capturing the full disk. The eyepiece's long, straight-sided housing provides a secure mounting point for smartphone adapters, ensuring the camera remains stable and centered over the optic for sharp, clear shots.
The 4-element design results in only four glass-to-air surfaces. Fewer surfaces mean less internal reflection and light loss, leading to higher light transmission and superior contrast compared to more complex eyepiece designs. This is why orthoscopics are renowned for their bright, crisp, transparent views.
| Focal Length | 18 mm |
| Apparent Field of View | 50° |
| Barrel Size | 1.25" |
| Optical Design | Classic Orthoscopic |
| Lens Elements | 4 |
| Coatings | HT Multi-Coated |
| Solar Projection Safe | Yes (Heat-Resistant Cement) |
| Filter Threads | Standard 1.25" |
| Net weight (kg) | 0.09 |
| Eye Relief (mm) | 14.67 mm |
| Field Stop Diameter | 16.8 mm |
| AR-Coating | High transmission multi-coated (HT-MC) |
| Optional Accessories | Q-Turret Eyepiece Revolver |
| Speciality | No Speciality (standard eyepiece) |
| Threaded for filters | No |
| Number of Groups | 2 |
| Dustcaps | 1¼" dustcap (31.8mm) |
| Eyecups | winged eyecup (1¼") |
| Slip Protect Safety | Classic Undercut |
| Eyepiece Body above Reference Plane (mm) | 30.46 mm |
| Length of 1¼" barrel (mm) | 24 mm |
| Eyepiece Series | Classic (Q-Turret) |
| Outer Diameter | 34.8 mm |
Baader Classic Ortho 18mm Eyepiece
× 1
Winged Eyecup
× 1
Dust Caps
× 2