The Blue Line 7–21 mm zoom eyepiece is an exceptionally affordable option that allows quick, smooth magnification changes across the 7 to 21 mm range. It performs well not only for astronomical use, but also for terrestrial observation. An ideal choice when keeping your setup lightweight and easy to use is a priority.
The eyepiece offers an apparent field of view of 35° to 52°, while its eye relief ranges from 24 to 18 mm depending on magnification. This ensures comfortable viewing even for eyeglass wearers. To reduce stray reflections, the optical elements feature multiple anti-reflection coatings, while the internal surfaces are finished in matte black.
The Blue Line optical design has been engineered to deliver good image quality, proper contrast, and balanced performance throughout the entire focal length range, despite its zoom construction.