20 Dec 2015 21:36
Stabilized telescopes are costly and rare (mostly binoculars), while autofocus ones seem nonexistent (fixed focus can work with basic capabilities). But camera lenses with autofocus and stabilization are cheap and increasingly excellent. A telescope (or half a binoculars) is essentially a long-focus lens with a secondary lens to adapt its refraction to the eye and, for terrestrial use, a prism to erect the image (undo the lenses' flipping the image upside down and backwards). Spotting-scope adapters for camera lenses such as the all-in-one eyepiece, prism and tripod foot "Lens2Scope", and simple telescope-eyepiece mechanical adapters, are available. So why not get the electronics working?
Canons, at least, require a "stabilization start" command from the camera in addition to power to trigger the optical stabilization, which beyond that seems to rely on sensors in the lens itself rather than measurements or computations from the camera. Tapping in wires from a camera mount or another lens will get it working. Tapping in wires from another lens, zoomed to the same distance if applicable, can even autofocus the lens one is looking through - or perhaps two, carefully aligned, for a binoculars. (Connecting two lenses' lens-to-camera direction wires to a camera may result in error messages and nonfunctionality, but simply leaving one lens's communication back to the camera ignored seems to work fine and often even allows its own electronic focus ring to work. Once-matched focus may eventually drift, but lower focus-drive speeds, as the 7Dii allows configuring in video mode, tend to reduce the incidence of that.)
Direct viewing through the lens gives a brighter, more magnified view than the camera's own viewfinder, which typically emphasizes visualizing defocus over brightness and clarity. "Eyepiece magnifiers" may be available for the camera but probably won't make a very good telescope. A camera aligned with the viewing rig could take a less-magnified picture of whatever you're watching.
Many eyepiece kits may not provide for a very wide exit aperture, under-utilizing fast supertelephotos. A 55-250MM STM or similar lens could be a great start.
An entire camera is a very bulky battery and microcontroller: for a more compact solution, generally without autofocus, try a battery, an "Arduino" or similar programmable tiny controller to send the focus commands, and customized eyepiece to camera-mount adapters to transmit the various necessary signals to various lens mounts without the need for modifying the lenses. Autofocus would require some sort of optical or distance sensor - perhaps a time-of-flight rangefinder for fast focusing on a point, and electronic commands to set the lenses to about the right distance with the eyes' natural focusing taking up the slack - but a simple program could replicate electronic focusing signals to pair up focusing across a binoculars.
Modification of a pellicle-mirror reflex camera (or perhaps a similar Sony reflex-to-mirrorless lens adapter) could allow viewing through the former image plane with continuous operation of phase-detect autofocus, and whatever other imaging system might now defer to the primary purpose of a great view.