Red Dot Sight Re-Visited

Started Jun 8, 2012 | Discussions thread
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KiwiBee
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Red Dot Sight Re-Visited
Jun 8, 2012

Here’s my variation on the red dot sight attachment-to-camera discussion that occasionally surfaces in the forum.

I have attached it permanently to a cheap Chinese-made tripod mount ring (eBay) that fits both my Tamron 200-500mm and Sigma 70-200mm lenses (the only ones I use for sports or birding).

The sight itself can be removed from the sight’s mount bracket if more compact storage is required, by removing the two small threaded machine bolts (that come with the NcSTAR sight).

While it is certainly possible to use the existing mount rings on the lenses, it is a little more ‘fiddly’ to attach and remove the sight each time you want to use it.

If buying a cheap ($8) ring like mine, ensure that it is advertised as a 72mm ring – mine was as follows:
Tripod Mount Ring for Canon EF 100mm F/2.8 USM Lens

Ring diameter inside : 72mm 
Ring breadth: 17.4mm
Ring thickness: 3.5mm
Color: black
Made by metal 
The UNC (Unified National Coarse Thread) is ¼ inch.

This one does not have a hinged opening so a little force is needed to spread the opening to slide it over the camera end of the un-mounted lens.

Note: not all mounts for that Canon lens are 72mm – some are advertised as 68mm!

The photographs should be self-explanatory, but basically I removed the adjustable dove-tail mount and replaced it with a 50mm length of angle alloy, drilled to accept the two original machine bolts and a shortened bolt to attach onto the mount itself. I added a spacer between the two flanges to prevent crushing.

It works perfectly. Any parallax error that occurs at close ranges can be easily allowed for with a little practice.

On the A77 it is very useful to have the LCD screen turned out and tilted up so that both the red dot on the sight and the Live View can be seen simultaneously.

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KiwiBee

Sony SLT-A77
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