Telescope camera mounting clamp

This is a camera mounting clamp for my Canon 600D so I can mount it on my telescope tripod .  It will allow me to mount the camera on the Equatorial tracking system (EQ3) so I can take long exposure astro-photography, of nebula, planets and the moon, also very good for taking multiple photos of meteor showers.  The telescope, which is a Sky Watcher D150 750, came supplied with a spare mounting rail so I have used that as the preferred method to mount on the tripod.


Materials used are mainly what I have lying around the workshop, so I had a few  PVC blocks which I used for the main body, brass for the small camera screw, black acetal for the clamping screw, red oilite plastic for the detachable mount.

Start with a suitable block of PVC, and mill two rebates to aid alignment on the mounting rail. Drill a 1/4″ clearance hole for a 1/4″ x 20tpi W allen head bolt.
Rough out the basic step shape, then work out the dimensions for the dovetail clamping arrangement, this required a lot of head scratching and guesswork, and many cups of tea!
Another block of PVC is used to make the sliding dovetail clamp. Once this is made I can use it as a template to make the female dovetail.
A slot is milled to the approximate middle of the dovetail, then the cutter is progressed into the block a few times until a good sliding fit is achieved.
The sides are fly cut to tidy it all up.
Over to the lathe and four jaw chuck to recess the block for the detachable mount. The outer diameter has a slight taper to aid secure fitting.
Now for the red plastic detachable mount. This has a recess for the camera screw and a tapered base. I have also recessed the top side for a felt pad. The screw is made of brass and is threaded 1/4W.
Making the brass screw
Slitting cutter being used for the screw head slot, this is about 2mm wide and enables the screw to be tightened with a coin.


Finished screw, note the recessed shoulder this will allow the screw to be screwed into the detachable mount but will be both slack and secure.
The clamping nut is made from black acetal rod which is really nice to machine. I thought it would look good with a concave top, next operation will be the peripheral notches which I prefer rather than a knurl.
Milling the six notches using my simple dividing head.
Nut done, looks good, acetal is a very tough engineering plastic and is ideal for jobs like this.
Little bit of fettling and tidying up, including a recess for the allen socket head screw, which also has a circlip on the underside for security.
Using a coin to secure the detachable mount to the camera.
This is how it all goes together on the tripod mount. The mount is first aligned with the North Star (Polaris) this allows the motorised tracking system to track the stars as the earth rotates, minimising the possibility of ‘star trails’ or streaks when using long exposure.  The rail also allows mounting onto the top of the telescope clamps (piggy back), using two 6mm bolts will hold everything secure.  Just need some good clear sky at night now!

The world of small engineering