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Info on CG-5 ASGT Motors and Revisions?

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#1 zAmbonii

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Posted 04 February 2013 - 10:51 PM

About 5 or so years ago I bought a used CG-5 ASGT off of Ebay for quite cheap. It has served me well over that time to get into some deep space and planetary AP. Of course I have had the same problems with stiction and stuff as many others have had. Took the whole mount and regreased a couple of years ago. Back in the summer I seemed to run into a flexture problem and never really got it straightened out.

A couple of weeks ago I ran across another CG-5 owner selling his mount head for parts, and I snapped it up. At $45 how could I pass? My goal was to see if the DEC axis acted better and get rid of the stiction problem. With the parts from two mounts I could get a better setup (was toying around with upgrading the mount before this came available).

The mount head arrived last week and gave things a look over this weekend. The mount had been in an "accident" (knew this before buying). It looks like the encoder end of the DEC motor took a direct hit and the encoder disk was shattered, the cap that held the encoder disk on was quite bent also. One of the leads to the RA motor is loose (but fixable) and the encoder disk looks fine. Came with the DEC motor cover, but no RA covers/board. They seem to have been busted in the accident also.

Funny thing is that the metals parts of the mount look like there is nothing wrong at all. No signs of anything taking an impact. The DEC cover looks perfectly fine also (strange because the DEC motor looks like it took a direct hit....maybe it happened with the cover off for some reason).

Over the weekend I was doing a search on the forums here and reading threads, I am convinced that the CG-5 that I am currently using is one of the really old versions. Although it has been about 3 years since to took apart the RA axis, I don't even remember having ANY of the wheel bearings in the axis. It looks like the RA axis shown on the astronomyboy website. Earlier tonight, I took the ring nut off, and I was immediately presented with the thrust bearing. I pulled apart the DEC axis quicklike and it looked the same as my current DEC axis.

Was wondering, other than the addition of ball bearings in the RA axis, has there been other major revisions of the mount over the years? Just wanted to be sure that I could use parts from one of the mounts for the other. Obviously, I cant really swap RA internals. Should the DEC internals be the same?

Did they make any changes in the motors from the older CG-5 versions to the newer ones? Also, is the RA motor and the DEC motor the same except for the shielding magnet attached to the connection cable on the RA motor?

The "new" mount hardware seems to be in really good shape. Just moving the axes around by hand, they seem quite smooth in motion. The DEC axis seems a little stiff, but that is probably because the previous owner looks to have regreased with some heavy red bearing grease. The surfaces look really good internally, I see very little wear anywhere. The races on the thrust bearing shows minimal sign of a groove.

This is my current plan:
1) Clean and regrease both of the axes. (Still have my old tube of superlube).
2) Reattach the power lead to the DEC motor, and test both of the motors from the "new" mount to see if they work.
3a) If the motors work - take the encoder disk/electronics from the old RA motor and place on the new one.
3b) If the motors don't work - just switch the motors from old mount to the new one
4) Take control board/RA internal electronics from old mount and put on new one.
5) Fire things up and cross fingers to see if things work right.

Anyone see anything wrong with this plan?

#2 RTLR 12

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Posted 05 February 2013 - 01:12 AM

Looks like a good plan to me. Let us know how it works out.

Stan

#3 skywolf856

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Posted 05 February 2013 - 12:29 PM

You can buy new boards and motors for it direct from C.

http://www.celestron...nomy/parts.html

#4 jrcrilly

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Posted 05 February 2013 - 02:33 PM

You can buy new boards and motors for it direct from C.

http://www.celestron...nomy/parts.html


Wow. It's nice that they make the parts available - but that's quite a price bump. They charged me $100 less for the CG5-GT motor/encoder assy I bought a few years ago. Of course, it was still in production at the time so they probably had them lying around.

#5 zAmbonii

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Posted 05 February 2013 - 04:46 PM

I have the board from the old mount so that isn't a problem.

I just got finished with an initial testing of the motors from the "new" mount....and it looks like I will just have to go with the old motors for now since I have no idea what is going on with the "new" motors.

I hooked the DEC motor up and it doesn't seem to want to run. I got a bump when trying to change directions (because of the backlash setting I had in the controller), but it doesn't want to turn. May be damage caused by the drop of the mount the previous owner had.

I reattached the broken lead on the RA motor, and when I hooked that up, it runs....BUT at full speed. Motor changes direction with input from the controller, but it is either full speed forward, or full speed backwards. Changing the rate on controller doesn't change anything.

Thought it may have something to do with the encoder disk, the RA disk was loose when I looked at it, and thought I may not have had enough clearance. When I tried to screw it back on (after looking at the disk on the old motors for a guesstimate of distance), I ended up cracking the slotted set screw....then ended up cracking the encoding disk when trying to tighten the screw with a pair of needlenose pliers.

Could the new motors be somehow different than the old ones? Again, I have no idea if they had changed/upgraded the motors over the years.

Looks like for now I am going to have to use the old electronics and motors from my old mount.

#6 zAmbonii

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Posted 05 February 2013 - 06:12 PM

Ok, I think the RA motor is fine...just an encoder problem. I disconnected the encoder from one of the motors on the old mount and it acted the same way. Didn't realize an encoder problem would cause the motor to run that way. At least I have one backup motor! YAY!

#7 zAmbonii

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Posted 07 February 2013 - 04:20 AM

Sat down tonight and did the regrease of both axes. The main differences inbetween my old mount head and the new one are two bearings in the RA axis the old one didn't have and 2) worm gear bearings that weren't in the old one. The old mound originally had some bad play in the worm gear that was kinda fixed by putting in a nylon bushing from home depot (man that was a long time ago).

The RA bearings really help. On the old mount, I could get it to move easily and smooth, but as soon as I put the scope and some weight on the mount, it became a bit hard to move around. Not anymore with the new RA axis with bearings, it moves nice and smoothly even with weight on the mount.

The DEC axis may be a work in progress. Even with it regreased, it moves smoothly, but it is a bit stiff. Hopefully it will loosen up a little with some useage.

There was FINALLY an opportunity to get the scope out tonight and I threw the C8 on and tried to beat the coming clouds. I first got a couple of images of Jupiter:

Posted Image
Jupiter 2/7/13 by zAmb0ni, on Flickr

I then loaded up EQalign to check out the PE of the mount and ended up with the graph at the bottom. NOTE: the Y-axis is wrong because It wasn't till after I recorded it that I figured out how to change the pixel size in my camera. So, the PE isn't 40arcsec, but is ~26 arcsec.

Attached Files








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