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" FT adapter does nothing to prevent the greased moving mirror..."

That is not the purpose of the FeatherTouch (FT).? FT is?a gear reducer that facilitates fine focusing. I guess I should not have included that sentence in that paragraph as it seems to have confused you.

If a bit of focus wander is that upsetting then an external focuser will sooth your pain.? But it is?not a necessity.?

I use?cameras with?very small FOV (6 arcmin) and am able to cope with the focus shift via the method previously described; i.e. always focus in the anti-gravity direction.? In my setup, focusing in the opposite direction will often move the star completely out of the FOV but then turning?in the correct direction brings the star right back.? It's not a problem.

Stan

It takes awhile to master the art of SCT focusing.? The key is to always approach focus from only 1 side - pushing against gravity.? If you go past then back-up and start again.? A "Feather Touch" adapter is a near necessity. Once you?master it, it's not that difficult.

External focusers can be easier but also?are potentially problematic due to the extended back-focus, weight limits, and?the varying the back-focus distance (some reducers require exact spacing with very small tolerance).

Stan

I didn't like the greased pole dancing moving mirror focuser on the C14 because of image shift, mirror flop, and the stiction inherent to a sliding focuser mechanism. I replaced the entire original C14 focusing mechanism with a compliant greaseless stictionless focuser of my own design. Shown below is the C14 mirror mounted on the new focuser that sits between the mirror and back plate. In addition to eliminating mirror flop and image shift the new focuser allows for collimation of the primary mirror/ focuser assembly from the C14 outside rear as shown below. A Robo-Focus motor is easily attached to the backlash free focus knob for motorized focusing, autofocus capability, and temperature compensation capability.

Don Clement

?

http://s72.photobucket.com/user/miltons_stuff/media/BackViewFocuserWMirror.jpg.html

http://s72.photobucket.com/user/miltons_stuff/media/C14MovingMirrorFocuser.jpg.html

I use an Optec Lupus .62x. works very well

CAH

I had a standard C11 and went to a C14HD. noticeable difference in flat field performance.? The C14 has some issues with focus and mirror flop so I would recommend using an OAG. I'm not sure if others have the same issue.?

The mirror?flop is an issue and I can't seem to resolve it. the mirror locks?help but engaging them changes focus enough to make a redo.?

The edge optics do not come into play if you use a hyperstar.? I have a C8 and a C9.25 I run with a hyperstar and use the C14 at F11 or F7 with an OAG.

CAH

The SBIG is a standard 17mm spacer so the camera shouldn't matter.? All Celestron Edge telescopes require specific spacing to you camera.? If you are running at native focal ration, you will need to get an adapter.? Starizona has some (I have that) but Celestron as well as others have the spacers you will need.? If you use a reducer (celestron or Optec) be sure to order the correct adapter for you scope and camera.

Clear skies.

CAH

I have a C11 Edge HD and an SBIG STT8300M ccd camera.? Does anyone have experience using a similar setup?? If so, what type of connectors and spacers are you using to connect the camera to the telescope?

Any comments would be most appreciated.

Rick

that dark band over the bottom polar cap?is interesting.

Thanks,

Stan

Seeing was pretty good for a while when this data was captured. This image is a combination of 3 sets of RGB data taken over 22 minutes:

Brian

" Starlight Feathertouch Crayford ... visual I don't think it's possible to use along with my 2" diagonal"

I don't see why not unless it causes the back focus to exceed the corrector's specs, which?may not be noticeable in the EP.? But I don't see much advantage to using an external focuser for Visual use.? The built-in focuser is right there next to your eye and SCT image shift is not a real?issue (unlike for some small cameras where?a focus star might shift off the chip).

As for cameras, there should be no problem at all adapting any camera to prime focus imaging with the external focuser. But things get a bit squirrely when using the custom reducer because it requires a?specific back-focus with very small tolerance.? (BTW, reduction is a?near necessity for the MallinCam, which requires a low f-ratio to work properly).??The reducer?virtually prohibits the use of an external focuser because that focuser varies the critical back-focus required by the reducer. The focuser?may be able to be inserted (check all the distances) but it could only be used to perform small tweaks in concert with the internal focuser and hardly seems worthwhile.

I wouldn't over-plan this. Don't sell (or buy) anything until you have some experience and experimentation?with the scope and truly know what is needed and not needed.

Stan

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