Specification Brand : GOWENIC BulletPoint1 : Universal Compatibility: Designed to work with all types of telescopes, reflectors, refractors, for Dobsonian, for Mak‑Cas, and for . It fits on astronomy telescopes with an outer diameter of 104‑146mm and can be easily attached to any telescope with the 3 bolt setup. BulletPoint2 : Focusing: Eliminate guesswork in focusing with the telescope focusing mask. It overcomes visual conditions and facilitates fast and easy optimal focus for your telescope. BulletPoint3 : Secure and Centered Positioning: The 3 metal posts clamp onto the telescope, preventing slipping and keeping the mask perfectly centered. The 3 post mount allows the mask to stay centered while accommodating a wide range of telescopes. BulletPoint4 : Efficient Star Focusing: As light passes through the focusing mask, it diffracts in 3 different directions, creating 3 pairs of star spikes. The pattern of star spikes shifts as the telescope's focus adjusts, indicating perfect star focus when the 3 spikes align. BulletPoint5 : Lightweight, Resilient Design: The fishbone focusing plate is crafted using lightweight aluminum alloy and is just 1mm thick. It ensures the balance of the telescope isn't disrupted and guarantees durability and longevity. ItemName : Bahtinov Mask Focusing Mask for Telescopes, Aluminum Alloy Bahtinov Mask Telescope Focusing Mask for OD from 104mm-146mm Astronomical Telescope YG100 ItemPackageDimensions_Height : 3 centimeters ItemPackageDimensions_Length : 16 centimeters ItemPackageDimensions_Width : 15 centimeters ItemPackageQuantity : 1 ItemTypeKeyword : eyepieces Manufacturer : GOWENIC ModelName : GOWENIC3hk6wvnie0 ModelNumber : GOWENIC3hk6wvnie0 PartNumber : GOWENIC3hk6wvnie0 ProductDescription : 1. Universal Compatibility: Designed to work with all types of telescopes, reflectors, refractors, for Dobsonian, for Mak‑Cas, and for . It fits on astronomy telescopes with an outer diameter of 104‑146mm and can be easily attached to any telescope with the 3 bolt setup. 2. Focusing: Eliminate guesswork in focusing with the telescope focusing mask. It overcomes visual conditions and facilitates fast and easy optimal focus for your telescope. 3. Secure and Centered Positioning: The 3 metal posts clamp onto the telescope, preventing slipping and keeping the mask perfectly centered. The 3 post mount allows the mask to stay centered while accommodating a wide range of telescopes. 4. Efficient Star Focusing: As light passes through the focusing mask, it diffracts in 3 different directions, creating 3 pairs of star spikes. The pattern of star spikes shifts as the telescope's focus adjusts, indicating perfect star focus when the 3 spikes align. 5. Lightweight, Resilient Design: The fishbone focusing plate is crafted using lightweight aluminum alloy and is just 1mm thick. It ensures the balance of the telescope isn't disrupted and guarantees durability and longevity.