This versatile 50mm aperture guide scope with a built-in helical focuser for precise focusing of potential guide stars.Designed for use with the guider CCD astronomy camera or eyepiece. It is an ideal accessories to any astrophotographers. Extinction design of telescope. Taper matt tooth and spray matting paint design can greatly reduce the light loss of light in the entire lens barrel, making the image clearer and sharper; Unique design with double protection to avoid loss of light, making the images you observe clearer and sharper. Lightweight and portable. 604g and 240mm total length that is very small and compact autoguiding system adds hardly any weight to an astrophotography setup. SV172 Dew Heater Strip is a good partner during frigid winter temperatures, condensation, frost, dew or fog days with high humidity. It warmed up quickly, fast removed the condensation from your lens, and held an even warmness all night to keep your glass clear. There are a device to let you adjust from off-to-low-to-high modes. You can change the the temperature by adjusting the regulator to meet your different needs. It keeps the lens warm so it doesn't form condensation. Perfect for any nighttime long exposure photography. Effective for keeping dew or frost off of your lenses. It seems to work well even when the outside temperature is quite low. The max diameter it will fit is 76mm. You'll have the decide for your lens. The SV172 band is 320mm long and 50mm wide. The heated portion of the wrap does not span the entire length. About 240mm is heating, others for velcro purposes. 66g / 2.32oz net weight will not be a burden for your telescope or camera.