Meade Variable tele-extender for SCT, needs T-ring

The tele-extender has two nested tubes that telescope in and out of each other. This varies the adapter's physical length, which changes the image size over a limited range without having to change the eyepiece. The telescoping tubes are held firmly at the desired length by thumbscrews. The tele-extender has internal antireflection threading for high contrast, and needs an optional T-ring.

The calculator to the right gives the photographic values based on the tele-extender being used when closed to its shortest length. When the tele-extender is fully extended, the photographic values all will be approximately 35% higher than the results given by the calculator. Intermediate tube extensions will give photographic values between these two extremes.