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I've used a combination of an Explore Scientific 2" dia. 2x tel-extender plus an 80 mm. extension tube at the end of 112 mm. of draw tube of my ES 127 mm., f/7.5 refractor to capture images with a Canon T1i. I use this combination satisfactorily for imaging almost all deep sky objects, but planets need to be larger on the camera's sensor. For that reason, I bought a 1-1/4" dia. ES 3x tel-extender. Unfortunately, that 3x tel-extender required 251 mm. of extension tubes beyond the end of a 103 mm. of draw tube in order to bring the object to focus. Adding all components together, including the 3x tel-extender itself, I had 421 mm. (16.57 inches) of stuff hanging off the rear of the scope's main tube, NOT including the camera body and its 1-1/4" dia. nose-piece! Does this arrangement sound reasonable? If I had to do a fast slew to an object with all that weight hanging onto the rear of the scope, I'm afraid there'd be whiplash damage ! How do you folks handle Barlows and tel-extenders of 3x and greater power? Bob Z.
Firstly, with the weather being not so great, I've been experimenting with various eyepieces and Barlow lens combinations to see what might be practical for planetary imaging. Don't laugh: I've even doubled up two 2X Barlows; the result was awful -- no surprise. I recently downloaded the latest version of BYEOS, and in reading the new User's Guide, I read about the 5X planetary shooting mode and then wondered if this is the maximum magnification I can get at prime focus? Is 5X planetary mode the equivalent to using a 5X Barlow or tele-extender without BYEOS? Thanks. Bob Z.