Crosshair & Reticle Telescope Eyepieces
- Focal Length: 25 mm
- Apparent Field of View: 40
Reticle eyepieces are essential for anyone interested in astronomy. These eyepieces attach to a finderscope or off-axis guider in order to center your telescope on your desired celestial object or guide star. Reticle eyepieces have been also been around for nearly as long as telescopes themselves. First used in sights for firearms, reticle eyepieces had a crosshair traditionally made of spider web or hair in order to accurately center a target on the sight. Astronomers noticed the usefulness of reticle eyepieces and outfitted them for telescopes.
Astronomical reticle eyepieces typically feature a wider field of view than most other types of eyepieces as well as the distinct crosshair design. The crosshair design has been drastically improved since the old days, with the design often etched into the optics or using wire crosshairs, for intricate, precise designs.
You will often see reticle eyepieces with many different designs, including crosshair variations and a unique set of optics. One feature that is sought after by many astronomers is illumination. With a red-illuminated reticle eyepiece, the crosshair is easier to see at night without sacrificing your dark-adjusted eyes.
Another feature to look out for is an astrometric reticle eyepiece. These eyepieces build on the simple crosshair shape seen in many reticle eyepieces but add additional ticks, marks, and measuring circles to measure a range of astronomical characteristics. Astrometric reticle eyepieces can be used to measure double star angular separations, position angles, planetary diameters, and lunar crater diameters, as well as many other useful astronomical measurements. These are excellent for advanced astronomers who are looking to go beyond observing celestial objects.