From the ManufacturerThe Deluxe Tele-Extender for Schmidt-Cassegrain telescopes is a hollow tube that allows you to attach a camera to your telescope with an eyepiece installed. By using the Deluxe Tele-Extender in combination with an eyepiece, you can increase your instrument's effective focal length to well over 10,000mm. And this corresponds with a matching increase in image size. This technique is known as eyepiece projection photography. The following formula can be used to determine approximate effective focal length:EFL = telescope focal length/eyepiece focal length x DF (the distance from the center of the eyepiece to the film)The Deluxe Tele-Extender is used for high-power lunar, solar and planetary photography as well as for extreme terrestrial photography. It fits over the telescopes eyepiece (even large eyepieces such as those in Celestrons Ultima line), and connects to the visual back of the telescope. Optional counterweights will be necessary to properly balance the telescope when using the Tele-Extender.To use the Deluxe Tele-Extender, remove the diagonal from your telescope and insert an eyepiece directly into the visual back. Place the Tele-Extender over both the eyepiece and the visual back, then attach your 35mm SLR camera to the back of the Tele-Extender using a T-Ring. The Tele-Extenders built-in safety device will help prevent your eyepiece from becoming accidentally dislodged.There are a few things to keep in mind when using this accessory. First, the image you'll see through your cameras viewfinder will be upside-down. Secondly, due to the extremely high magnifying effect afforded by this accessory, you'll get best results by taking extra care to prevent camera and telescope vibration, to ensure accurate polar alignment, and to use under good seeing conditions.Product DescriptionThe Celestron Deluxe Tele-Extender is an SCT imaging accessory that allows you to take pictures through an eyepiece, for high magnification shots of the Moon, the planets, and the Sun (with the proper filtration). To use the Deluxe Tele-Extender, remove the diagonal or any other accessories attached to the visual back of your telescope. Insert the 1.25â eyepiece you want to use into the visual back and lock it firmly into place with one of the setscrews. The eyepiece must have a diameter smaller than 45 mm, which is the inside diameter of the Tele-Extender. Many eyepieces are too large, so double-check the fit before you begin your astrophotography session. For the most secure connection, remove the second thumbscrew from the visual back body and then slide the Tele-Extender over the inserted eyepiece as well as the visual back. When engaged, the two thumbscrews on the Tele-Extender clamp onto the visual back to hold everything firmly in place, assisted by a safety shield that keeps the thumbscrews from loosening during use. The camera side of the Deluxe Tele-Extender accepts a standard T-ring (sold separately). Remove the lens from your digital SLR and attach the appropriate T-ring. Screw it onto the t-threads of the Extender, make sure everything is tight and locked down correctly, and you are ready to take a picture. Remember, the image is not the only thing that will be magnified when doing eyepiece projection photography! Any problems with seeing conditions will become much more apparent, as will unintended movements of the telescope. Extra precautions taken to keep your telescope stable will help you achieve better results, including the use of a cable release to depress the shutter button for you. With a little experimentation, you will be taking high magnification images of solar system and terrestrial objects in no time! Â