Crayford focuser for an Edge scope

[hrgreen]

Wanting a better focuser for my CGEM 9.25 Edge, I had to consider whether using an eyepiece focuser would extend the back focus too much. The Edge 9.25/11/14 models are specd as having the best sensor image at 5.75" (146 mm) from the large adapter nut. Although visual is not as critical, I was getting very sharp stars out almost to the edge of the FOV with a Nagler 31 and a Panoptic 35 without a focuser, and didn't want to see coma, spherical and aperture reduction because of inserting one. The techies say that adding X amount of back focus is like adding 3X amount of focal length.

I tried a Moonlite with 3.29" thread, a beautifully made unit. But the thickness did cause some noticeable deterioration. Plus, it was quite heavy. Moonlite was kind enough to let me return it.

The dimensions and weight of the FeatherTouch 2008BCR with 3.29" adapter looked better, so I ordered it. With an Opt diagonal using a 2" nosepiece, I measure about 6.2" from the back to the 2" EP ring (with the focuser racked all the way in), only slightly over spec. And the FOV's still look very good. I recommend this possibility for Edge 9.25/11/14 scopes; don't think it would be as good on an 8.

Hal

[Tinker1947]

i put a Starlight Feather touch on C11 replaced the stock focuser, its a real pleasure to fine tune now.....

http://www.firstlightoptics.com/starlight-instruments-feathertouch/microfocuser-for-celestron-c11-sct-edge-hd.html