Last updated: 31 October 2003
Sent: Wednesday, October 29, 2003 18:48:45 From: firstname.lastname@example.org (Dan Grabenstein) After modifying my Crosman Red Dot Finder to reduce the dot intensity I built a removable mount for my ETX 70AT. All the parts were purchased at the loval Home Depot, and include: a.. 4" coupling ( styrene ) SKU 52063 40405 $ 2.58 b.. Aluminum plate 1/8 x 3/4 x 36 " SKU 30699 44710 $ 2.79 c.. 2 ea 3/16 x 3/4 " Aluminum Binding Posts SKU 30699 43901 $ 1.72 d.. 4 x 4 " Velcro sets ( w/ adhesive back ) ( I had on hand ) about $ 2 e.. 14 " Multi purpose Ties SKU 728494151489 ( pkg of 8 ) $ 1.55 Slice a section about 2 to 2 1/2 " out of the coupling. It has a ridge in the inside dividing it approximately in half. I shaved the ends of the ridge so it would fit the curvature of the OTA better. Drill two 3/16 " holes about 1 1/2 to 2 " apart and push the long piece of the binding post in each hole. The fit was tight enough that I didn't bother to cement them in. Cut a piece of the thicker part of the velcro set to fit each half of the coupling arc and attach the velcro covering the head of the binding post. Cut a 1 1/2 to 2 " long piece of the aluminum plate and drill two 1/8 " holes along the center line of the plate. I used an 8-32 tap to thread one of the holes and reamed out the other hole with a rat tail file in order not th have to drill the holes with great precision. ( it was easier to drill the holes in the approximate location of the binding posts and ream one to make a good fit ) Rather than use the large head screw that came with the binding post, I used a standard 8-32 x 3/4 " screw. This makes it easier to mount the Crosman finder using its own mounting hardware. The next step is to mount the Crosman on the plate. Since the plate is 3/4 " wide I had to replace the 3/4 " long screws that came with the Crosman with 1" long screws. The mating piece of velcro is attached to the ETX OAT directly in front of the eyepiece. Simply using the velcro attachment holds the Crosman securely to the OTA, but it has a lot of "slop". In order to firmly mount it in place use the 14" tie, one in front and one in the rear. Doing this the Red Dot Finder is quite firmly mounted, and with the 3/4 " high binding posts, you can sight through it with the 25mm eyepiece mounted. You can see the finished product mounted and up close in the attached pictures.
Return to the top of this page.
Go back to the Tech Tips page.
Go back to the ETX Home Page.