SV197 cheshire collimating eyepiece can be inserted into 1.25 inch focusers or diagonals. How To Collimate Telescope With Cheshire Eyepiece: The view through the Cheshire eyepiece during the collimation will differ between telescopes. For fast telescopes (f5 and below), it will be little off-center, and for the slow telescopes (f5 and above), the view will be more centered and easier to collimate. 1.The goal here is to center the primary mirror reflection in the secondary mirror and reflection from the Cheshire with the secondary mirror. 2.To achieve that, you have to use the adjustment screws on the secondary and primary mirrors while looking through the Cheshire eyepiece collimator tool. Steel Crosshairs. The cross-hair adopts strong and durable steel wire instead of easily broken copper wire or aluminum wire. EVA lined packaging. Ensure transportation safety and easy storage. This 3x Barlow lens allows you to triple the magnification of any 1.25" eyepiece and deliver stunning image quality without adding a long reach between the telescope and eyepiece. 3x magnification with 1.25" interface. The magnification of the Barlow lens is 3X, which can magnify the image without the Barlow lens by 3 times. You can see more details of the moon and planets, and the image is clear, making your observation more comfortable. Black matt treatment. The blackening of the edges of the Barrow lens and the internal blackening process can minimize the reflection of light during the refraction process, maximize the saturation and contrast of the image color, and make the image edges clearer. SVBONY 4mm 1.25" fully coated eyepiece is perfect for broad field lunar observations medium sized star clusters and wide range of cloudy nebulas;deep sky targets. FMC glass optics increase light transmittance; Enhance details on jupiter; saturn; Mars; venus. Standard 1.25" 31.75mm fitting diameter, can be used in any astronomical telescope with a 1.25" focuser.