The Baader Hyperion Eyepiece 5mm delivers a 68° field of view with 20mm eye relief. Hyperion eyepieces feature Baader's ' Phantom Group' multicoating, sharpening contrast & ensuring excellent light transmission. Each eyepiece has both a 2" & 1.25" barrel & is equipped with both a M43 & SP54 photographic thread, housed under a protective silicone rubber ring. The photographic threads may be used in conjunction with an adapter ring in order to attach to a wide variety of photographic equipment. A variety of focal lengths can be achieved with the use of optional accessories, such as the 2" Finetuning rings (14mm & 28mm) & 2" eyepiece filters. The effective modified focal length when used in conjunction with fine tuning rings & filters is listed under 'further details'. To work out the magnification of your setup, divide the focal length of this eyepiece (5mm) with the focal length of your telescope.