High-quality, accurate instruments with excellent optics are popular with both beginning and professionalnavigators. Constructed from lightweight, corrosion-resistant aluminum, the Astra IIIB iselectrically lighted by LED on the arc and drum. Rectangular index mirrors are standard on bothmodels, though mirrors on the Astra are easily and conveniently interchangeable. The traditionalhalf-silvered mirror is preferred by many experienced mariners, while the whole horizon mirror isoften easier for beginners to use. A 3.5 x 40 monocular telescope is also included. Frame Material: Aluminum Sighting System: Traditional half-silvered or whole horizon mirror Scope Magnification: 3.5 x 40 Filter Shields: 4 index - 3 horizon Arc Range: ±20", throughout the arc Drum Calibration: -5° = 130°, radius 153mm Lighting: LED on the arc and drum Weight: 2.6lbs Case: Varnished wood carrying case Included Accessories: Case, instruction book, certificate of accuracy,vial of oil, adjusting wrench Warranty: 30 Days