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ES Twilight II altitude motion

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#1 kwjohnson

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Posted 25 May 2013 - 09:25 AM

Has anyone noticed the ES Twilight II altitude motion getting tighter over time? I have a C8 on one side and an ADM dovetail with about 10 pounds of counterweight on the other side. The motion isn't unusable but it takes a bit of a shove compared to the azimuth.

#2 Jim7728

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Posted 25 May 2013 - 01:35 PM

I assume the C-8 well is balanced on the altitude axis in that the tension knob is only slightly tight.

Maybe some dust contaminated the altitude bearing surface and needs a cleaning. Not sure if to access it just involves removing a tangent arm and slipping out the altitude bearing assembly.

#3 XyrcesFenol

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Posted 25 May 2013 - 01:58 PM

What is the weight on the C8 side with eyepice, diagonal, etc?

#4 kwjohnson

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Posted 25 May 2013 - 04:13 PM

The C8 EdgeHd + diagonal + F50 finder + ES68 34mm comes in at about 20 lbs.

I have an ADM dovetail on the other side that carries 11 lbs. of counterweight. ES says the counterweight isn't necessary, but there's a little less stiction with it in use.

I'm going to cautiously take it apart and see if it's gunked up.

#5 Jan Owen

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Posted 25 May 2013 - 04:31 PM

Once you've found what was causing the extra friction & fixed it, please update us with what you found & what you did to fix it... Good luck!!!

#6 kwjohnson

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Posted 25 May 2013 - 05:06 PM

Will do. I have some more experimenting to do!

#7 kwjohnson

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Posted 25 May 2013 - 07:39 PM

I've got it back to what I recall as the original smooth movement.

I wasn't able to completely disassemble the altitude parts, but I was able to remove the saddle, silver retaining ring, and black nylon washer on each side. I could barely rotate the altitude motion by hand at that point, but was able to shove the assembly over to one side. I found a couple things--the usual thick grease that looked like it had accumulated some grime, plus some black thread-like pieces that looked like they had been shaved off the nylon washers or some internal part I couldn't get at. I wiped off the grease, added a little Novagard G661 Silicone Compound (same lubricant I use on the azimuth), and reassembled.

The only hiccup was that I had inadvertently moved something about an eight of an inch to one side, so that one of the silver retaining rings was obviously jutting out further than the other. (The part was a black ring inside one of the side holes--not sure how to describe it other than that.) With the whole assembly back in place, I gave one saddle a tap with a washcloth-covered hammer and everything slid back to center.

Before I started this adventure the altitude motion had been stuck to the point that the scope needed only a very rough balance and needed way too much pressure to move. Either the grime or the nylon threads might have been enough to hang it up. Now it moves easily (maybe a little too enthusiastically) so that the altitude needs the top tension knob engaged just a little to be able to change eyepieces without the scope moving.

Jim, thanks for the input to look for grime. That seemed to do the trick.

Kevin

#8 Jan Owen

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Posted 09 September 2013 - 03:54 PM

Now that several more months have passed since you cleaned the altitude bearing area, how is the mount doing??? Still smooth & easily movable in both axes?

Been considering buying one myself, but there's very little owner feedback out there... Any idea what kind of bearings, if any, are used in both axes? Or just metal on metal with grease as a lubricant?






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