Feature: 1. Excellent Optics: The guide scope features 3 layer ED glass with outstanding resolution and virtually no chromatic aberration, along with wide band multi layer coated lens for bright and clear images. 2. Versatile Compatibility: Supports single tube guiding for photography within a 1/3 inch imaging circle, with a premium 130mm guidescope providing excellent guiding accuracy. Also supports dual tube merging with compatible binoculars (adult pupil distance of the normal value of 58 to 64). 3. Light and Sturdy Construction: The lightweight yet sturdy carbon fiber optical tube assembly makes this guidescope a reliable guiding and aiming tool, with three 1/4 inch screw holes at the bottom for use with dovetail rail. 4. Easy Eyepiece Installation: Compatible with standard 1.25 inch eyepieces for direct focusing, serving as a finder scope or viewing scope. Simply twist to tighten the eyepiece mounting interface. 5. Ideal for Astrophotography: Compact and lightweight, the guide scope is equipped with 40mm wide angle achromatic lens, making it a fantastic accessory for astrophotography. Specification: Item Type: Guide Scope Material: Aluminum Alloy, Optical Glass Item Number: 5P9976C Objective Diameter: 40mm/1.57in Lens Focal Length: 130mm/5.1in Focal Ratio: F3.5 Objective Structure: 3 Piece Design (2+1) Image Circle Size: 1/2.7 (for Premium Guidescope and Small Format Camera Deep Space) Angle: 2.96 Degree Temperature: -20+80 Overall Length: Approx. 154mm/6.1in (with Extension Ring 166mm/6.5in) Adjustment Range: 14mm-0.5 End Interface: 1.25 Inch Interface Thread Specification: M42x0.75mm (T2 Interface) Base Interface: 1/4 Inch Screw Interface x 3. Package List: 1 x Guide Scope 2 x Screws Note: When installing the guidescope, there is a 1/4 inch screw hole at the bottom connection, which needs to be used with the dovetail guide rail.