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CG-5 Goto mount problem...

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#1 Agnosticus

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Posted 12 April 2010 - 07:46 PM

Hi everyone,

For whatever reason, my used (but newly purchased) Celestron CG-5 GOTO mount is acting like it's possessed. When I turn it on, put in all the requisite info, and start the automatic 2-star alignment, it ends up slewing...and slewing...and slewing, until it's pointed at the ground. Then it keeps intermittent little movements indefinitely (until I end up having to switch it off). Any ides?

#2 hfjacinto

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Posted 12 April 2010 - 07:51 PM

I never had this issue, but I have had slew speed up or slow down. Check the battery connection, it might be loose. I usually use a knife to pry apart the connection and that seems to always help.

#3 jfusto

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Posted 12 April 2010 - 07:59 PM

Are you polar aligned before you start the 2-star alignment procedure?

#4 RTLR 12

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Posted 12 April 2010 - 08:09 PM

Sounds like a power issue. Check your power supply, cables and connections. You will also need to do a factory reset and re-enter your info and settings.

Stan

#5 Agnosticus

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Posted 12 April 2010 - 09:57 PM

Yep, polar aligned. It seems to be powering up OK (using their cig lighter car adapter), though perhaps the connection needs to be cleaned. I will try the factory reset as well. Thanks!

#6 Fred1

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Posted 12 April 2010 - 10:01 PM

Are you sure you're getting at least 11-12V from your power supply?

#7 RTLR 12

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Posted 12 April 2010 - 10:12 PM

You had better make that 12-13V. At 11 volts you will have problems...

Stan

#8 Chris Rowland

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Posted 13 April 2010 - 02:41 AM

If the power and factory reset solutions don't work then it could be a problem with the connections to the motors. If the encoder signals are bad the controllers don't know what the motors are doing and tend to keep driving them.

Check all the cables and connectors to the motors, inside and out. It may help to push the cables a bit further into the IDC connectors.

Chris

#9 guyinthesky

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Posted 13 April 2010 - 06:33 AM

if the car is not running its only getting 12 volts, try it with it running, 13.8 volts.

#10 Agnosticus

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Posted 13 April 2010 - 06:38 AM

Great suggestions. I will try them and get back.

Thanks again, gang!

#11 Javier

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Posted 13 April 2010 - 06:50 AM

Kevin,

This sounds like a power issue. Does the display on the hand controller glow a steady red color or does it sort of fade in and out? I learned that the CG-5 and probably all Go-to mounts are very sensitive to power fluctuations.

#12 Agnosticus

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Posted 13 April 2010 - 08:56 AM

The illumination seems to be pretty consistent.

One other question: with what do you clean the connections? A q-tip will no doubt snag on the little prongs in the cables and the jacks. Use a little brush? Dampen it in alcohol?

#13 Eddgie

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Posted 13 April 2010 - 11:55 AM

I don't think it is a power problem. If the power is interruped even for the briefiest instant, the hand controller will reset and you would have to go though the setup again.

I have heard reports that some power supplies with noize will cause problems, but there should be a ferrite core on the power cable (maybe Inch long, half inch diameter plastic housing on the power cable). The role of the ferrite core is to suppress noise and spikes on the power signal.

Still, it is impossiblet rule this out, so the easiest thing to do us plug it into a car cigerette lighter.

Otherwise, I think you have a problem either inside the mount (which I think is unlkely) or with the connections inside the RJ jacks on the mount.

I have had this problem with 3 different mounts in the past. Two were LXD-55s, and one was with a CG5.

The RJ ethernet/Telephone type jack on the housing has tinly little springy metal fingers that press against the pin on the end of the plug on the handset cable. I think that if these loose tension or get any corrosion on them, the signal can be interrupted or corrupted.

I have used a very tiny spring hook tool to pry under these spring contacts and VERY VERY gently "Form" them back up a bit and this has cured intermitttent problesm on these three mounts AND on my CGE, which used to somethimes have runaways.

I don't think it is as likley that there is a problem inside the housing. It couldbe though, and if reseating the dec and RA cables severla times to wipe the contacts (they are self wiping and unplugging and re-plugging can acutally wipe off slight corrosion) or re-arching the springs contacts doesn't work, then it may be necessary to open the housings and reseat the internal plughs, but again, I think this is not a likely cause of the problem.

Contamination on the face of the emmitter disk can cause pointing errors, but the Calibration proceedure I think attemtps to account for a blocked emmitter disk windows.

Your problem sounds more to me like signal distortion.

Good luck.

#14 rmollise

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Posted 13 April 2010 - 04:58 PM

Hi everyone,

For whatever reason, my used (but newly purchased) Celestron CG-5 GOTO mount is acting like it's possessed. When I turn it on, put in all the requisite info, and start the automatic 2-star alignment, it ends up slewing...and slewing...and slewing, until it's pointed at the ground. Then it keeps intermittent little movements indefinitely (until I end up having to switch it off). Any ides?


This is symptomatic of poor power. First step in troubleshooting is to try an alternate power source, preferably a fully charged battery not resident in an automobile.

#15 Agnosticus

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Posted 13 April 2010 - 09:31 PM

Not the power... I made sure of that tonight. I also opened up the housing and ensured the connectors were well seated. I didn't open the DEC housing yet, though. I also haven't cleaned the controller or other jacks yet since I have no contact cleaner. Nor have I tried to gently pry up the connector prongs.

#16 Agnosticus

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Posted 13 April 2010 - 09:35 PM

I should also add: If I turn the thing on, if I don't do anything at all for long enough, it will just start slewing on it's own. I hope I don't have to ship this to Celestron. It's not under warranty anymore.

#17 Agnosticus

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Posted 13 April 2010 - 09:51 PM

One last (probably very relevant) detail. When I do my 2 star alignment, I tell it to go to Capella first (since it's fairly high in the sky). It goes approximately to where Capella is, but the little spinny icon in the hand control screen just keeps spinning... then the 'scope proceeds to slew around and point at the ground. Then it will just stop for awhile... scoot a little... stope awhile..etc... It goes through this same process every time.

#18 rmollise

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Posted 14 April 2010 - 07:07 AM

Not the power... I made sure of that tonight.


How did you make sure of that? It sure _sounds_ like power problems. Failing that, your best course is "Call Celestron."

#19 Fred1

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Posted 14 April 2010 - 01:06 PM

Perhaps the power switch is corroded and not making good contact. Doesn't cost much to replace one. I'm pretty sure this is the one, if you decide to go that route.

#20 dwitek

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Posted 14 April 2010 - 07:12 PM

Just yesterday I received a used CG-5 and mine does the EXACT same thing. It slews close to where the first alignment star should be (it's still daylight), stops for about 10 seconds but the "working" Icon keeps spinning. Then, the scope starts slewing, in dec only, for about half a revolution. Then, it pulses in the same direction until the dec cord wraps itself around the housing and I have to stop it or else it will rip the cord apart.

I checked the raw voltage from the power supply and it shows 15.2 volts. But, this is without a load.

I've reset to factory defaults but I understand that there are some values that don't get reset. The reset command only resets values stored in the hand controller, not the mount itself.

This is my first Celestron equipment and I know everyone raves about this mount but I'm quite disgusted.

I will add that the person that sold the mount to me forgot to send the factory Dec motor cord so I made one myself. It is flat, 6 wire telephone cable with the proper ends for 6 wire but is not shielded. I only mention that because I was reading that the CGEM uses a shielded cable but I could not find any info on the specs of the CG-5. The seller is sending me the factory cord but it's clear tonight so I made my own.

ADD 20:37: I notice that the RATE key changes the slew rate in RA but Dec stays at maximum speed no matter the setting. Is this normal? Could it be related to the homemade cable?

#21 Eddgie

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Posted 14 April 2010 - 08:14 PM

I don't think these cables should be flat. They should be twisted pair. The twist in a data cable greatly reduces interference from outside sources.

And again, any intermittent connection I think will cause most of the symptoms mentioned in the OPs post and your own.
You may want to check the contacts in the RJ jacks. De-ox maybe.. I don't know. I fixed mine by gently forming up the spring contacts inside the RJ plugs on the mount.

Of course you problem cold be totally different than the problem I had, but I had it with 3 different mounts and was able to improve operation just by doing the above.

I have to confess though that it doesn't even make sense to me. The RJ Jack was invented by the phone company to be hyper-reliable and it is a brilliant design.

And yet I have had LXD and CG5s and my CGE all experience run-aways, and cleaning the contacts and reforming the spring contacts seems to have elminated the problem ever time.

Anyway, could be someting else entirely.

Regards.

#22 dwitek

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Posted 14 April 2010 - 08:53 PM

Update on mine:

I swapped the motors from RA and Dec and the problem moved with the motor. Now the RA does the exact same thing and the Dec motor stops where it should. It looks like, at this point, that a new motor is in order. I've not looked into this particualr motor before but I'm going to check to see if there is an issue I can spot inside the cover on the back. Maybe the encoder is covered or loose. On my LX200 you can see the encoder but this is more sealed.

Will update in a little while.

#23 jrcrilly

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Posted 14 April 2010 - 09:00 PM

On my LX200 you can see the encoder but this is more sealed.

Will update in a little while.


The back cover snaps off and reveals the encoder wheel.

#24 dwitek

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Posted 14 April 2010 - 09:18 PM

There is nothing obviously bad about the encoder. It had some grease on it so I cleaned it off but it acts the same. I adjusted it very close then far away from the LEDs and that didn't change anything.

I mentioned that changing the slew rate only effected the RA. Since the motor swap that problem has also moved so it HAS to be an internal motor issue. I will order one from Celestron unless someone has a better, and/or quicker, source for it.

Agnosticus, you may want to try the motor swap and see if the problem moves with it.

#25 rmollise

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Posted 15 April 2010 - 06:39 AM

Just yesterday I received a used CG-5 and mine does the EXACT same thing. It slews close to where the first alignment star should be (it's still daylight), stops for about 10 seconds but the "working" Icon keeps spinning. Then, the scope starts slewing, in dec only, for about half a revolution. Then, it pulses in the same direction until the dec cord wraps itself around the housing and I have to stop it or else it will rip the cord apart.


Well, your problem is in declination, and you replaced the declination cable, so _I'M_ thinkin' that might just be a suspect. ;)






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