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Equipment Discussions >> Mounts

Pages: 1
RobbW
sage


Reged: 02/09/10

Loc: Elgin, IL
RA motor going haywire on a CG5-GT mount
      #4469994 - 03/23/11 11:33 PM

I have a Celestron C8-CF XLT on a CG5 Advanced Series Go-To mount that I bought used last year. I am having a problem with the RA motor. At least once or twice during an observing session, I will punch in a new target. The mount will start slewing. About halfway to the target (or sometimes almost all the way), the RA motor will suddenly drop from its high-speed slew down to a very slow speed (equivalent to Rate 5 or 6 on the hand controller) and continue slewing at this slow rate right on past the target. It will not stop until I push one of the direction buttons on the HC. A few times I have let the RA axis keep going just to see what happens, if anything. It just keeps going and going. Once it came very close to knocking into the bottom of the mount.

I've searched around on the 'net for this issue. I have found a lot of posts regarding runaway RA or DEC motors where the axis would suddenly start slewing at a high rate and not stop. My problem is exactly the opposite. It will slew to target at a high rate and then come to a crawl and just keep crawling without stopping.

I was hoping that maybe a tuneup would solve my problem. I just finished performing a DIY Hypertune(TM) service on my mount last night. Got it all put back together and tested it out today. I just have it set up on the tripod without the OTA on it. Nope, still having that same intermittent problem. So, it obviously has nothing to do with with the OTA since it happens when the OTA isn't even on the mount.

Anyone have any ideas or a similar experience? Thanks!


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Trev
scholastic sledgehammer


Reged: 12/18/05

Loc: Fort McMurray, AB
Re: RA motor going haywire on a CG5-GT mount new [Re: RobbW]
      #4470122 - 03/24/11 01:02 AM

Possibly an encoder problem? Since you've had it apart already why don't you try switching the motors to see if the problem persists. If it does I'd say you have a wire problem or a problem with the board. If it switches to the Dec axis then it's in the motor housing.

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RobbW
sage


Reged: 02/09/10

Loc: Elgin, IL
Re: RA motor going haywire on a CG5-GT mount new [Re: RobbW]
      #4470142 - 03/24/11 01:25 AM

Okay, I've been playing around with just the mount (sans OTA) some more. I turned it on, set the index marks, verified time, date, time zone, etc. I then started to perform the 2-star alignment. The first star up was Capella. I press Enter and off it goes. Now, I'm standing in front of the mount/tripod with the polar axis pointing right at me. As the mount heads towards Capella, the RA axis is turning counterclockwise. It gets to about a 45 degree angle and suddenly stops dead, then immediately reverses and starts turning clockwise at that very slow (but faster than sidereal) rate. As I look closer, it turns out that the DEC axis is turning, too, but so slowly it is nearly imperceptible. Anyway, the RA axis keeps slowly turning clockwise until the RA motor housing almost knocks the other side of the mount. I press a direction button to make it stop. I repeat this entire process a couple more times starting with the power off and proceeding to the star alignment. Each time, the RA axis stops at about the same point then reverses at a slow rate.

After the last attempt at a star alignment, I went in and reset the mount back to factory settings hoping this might clear out some messed up settings. Power off, back on, confirm time/date, and proceed to alignment. Same thing happens again.

Now, I dive into some of the deeper settings in the Scope Setup menu. I notice there are settings for Filter Limits and RA Limits. Would these have anything to do with my problem? Is it possible my mount just keeps hitting some sort of limit and slowly backs off to avoid scope damage?

Under the RA Limits menu, I set it to Disable Limits. Power off, power on, and then star align. This time it actually positioned itself to where Capella should be and let me move on to the next star, Procyon. On its way to Procyon, the RA axis is turning clockwise at a high rate slew. The RA gets to nearly a horizontal position and suddenly starts moving at that same slow rate again. It keeps turning slowly indefinitely until I press a button just before the RA motor casing knocks into the mount again.

I go back into the RA Limits menu, and it appears that the Disable Limits command did not save after the last power cycle. Oh well, I'm done messing with this thing for tonight. I did check the settings for the RA Limits. East was at 90 and West was at +00. Or were those the settings for the Filter Limits? I can't remember! There was some other limit setting that was at -6 degrees and +6 degrees. Does any of that mean anything to anyone?


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RobbW
sage


Reged: 02/09/10

Loc: Elgin, IL
Re: RA motor going haywire on a CG5-GT mount new [Re: Trev]
      #4470146 - 03/24/11 01:31 AM

Hey Trev, thanks for the insight. I think you posted while I was typing up my second post. I'd hate to have to tear this thing apart again after taking 3+ days to Hypertune it. For now, I'll sit and wait and hope that someone points out that I'm just an idiot and have some limit settings wrong or something simple like that.

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rmollise
Postmaster
*****

Reged: 07/06/07

Re: RA motor going haywire on a CG5-GT mount new [Re: RobbW]
      #4470293 - 03/24/11 06:23 AM

Quote:

I have a Celestron C8-CF XLT on a CG5 Advanced Series Go-To mount that I bought used last year. I am having a problem with the RA motor. At least once or twice during an observing session, I will punch in a new target. The mount will start slewing. About halfway to the target (or sometimes almost all the way), the RA motor will suddenly drop from its high-speed slew down to a very slow speed (equivalent to Rate 5 or 6 on the hand controller) and continue slewing at this slow rate right on past the target. It will not stop until I push one of the direction buttons on the HC. A few times I have let the RA axis keep going just to see what happens, if anything. It just keeps going and going. Once it came very close to knocking into the bottom of the mount.

I've searched around on the 'net for this issue. I have found a lot of posts regarding runaway RA or DEC motors where the axis would suddenly start slewing at a high rate and not stop. My problem is exactly the opposite. It will slew to target at a high rate and then come to a crawl and just keep crawling without stopping.

I was hoping that maybe a tuneup would solve my problem. I just finished performing a DIY Hypertune(TM) service on my mount last night. Got it all put back together and tested it out today. I just have it set up on the tripod without the OTA on it. Nope, still having that same intermittent problem. So, it obviously has nothing to do with with the OTA since it happens when the OTA isn't even on the mount.

Anyone have any ideas or a similar experience? Thanks!




It's probably not an encoder problem, and a tuneup will not help. This comes from insufficient power. Check all connections and your power cable. Spread the pin halves on on the mount-side connector, and, most of all, always operate off a fully charged, good battery. Had the same thing happen to me with my mount when it was new six years ago.


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orlyandico
Post Laureate
*****

Reged: 08/10/09

Loc: Singapore
Re: RA motor going haywire on a CG5-GT mount new [Re: rmollise]
      #4470296 - 03/24/11 06:33 AM

What Uncle Rod said.

I was also gonna say bad power. Perhaps a good power supply would help.

3 days for a hypertune seems excessive though!


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RodgerHouTex
Pooh-Bah
*****

Reged: 06/02/09

Loc: Houston, Texas, USA
Re: RA motor going haywire on a CG5-GT mount new [Re: orlyandico]
      #4470769 - 03/24/11 11:24 AM

Bad news, I am in the process of returning a brand new CG5-GT mount with similar issues on the dec. axis. Power was good and I even had the "new" round power cable from Celestron.

If it was me, I would probably try flashing the motor controllers and the handset and see if that works.


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RobbW
sage


Reged: 02/09/10

Loc: Elgin, IL
Re: RA motor going haywire on a CG5-GT mount new [Re: rmollise]
      #4471212 - 03/24/11 03:24 PM

Thanks, Uncca Rod. I will try another experiment tonight. I was running my mount off of a 12V AC wall adapter. So, I assumed that would provide good, steady power. However, it is not an official Celestron power adapter. It is one I had laying around that was the right voltage and polarity. Tonight, I will try running my mount from a fully charged battery and see if that makes any difference. If it does end up being an insufficient power adapter, what one should I use? I have my batteries for field use, but when I'm just out in my backyard, I'd rather run off of steady, reliable house power. Is there a suitable adapter I can pick up from The Shack, or do I have to order a specific one from Celestron? Thanks.

Quote:

3 days for a hypertune seems excessive though!




I only had 2-3 hours to work on it at night after my daughter went to bed. So, I had to spread it over three days. Plus, I'm kind of anal and OCD about that kind of stuff.


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germana1
professor emeritus
*****

Reged: 05/14/09

Loc: New Jersey
Re: RA motor going haywire on a CG5-GT mount new [Re: RobbW]
      #4471401 - 03/24/11 04:40 PM

Hi try this to see if the encoders are reading as I have the same problem in dec mine is not a power issue in hand controller go to get ra & dec and see if the encoder reading changes turn it on do a mock align then get ra dec and see if the readings change when You move up down left and right numbers should change My dec stayed at 90 deg ra changed on mine now waiting for dec motor hth Pete also I am fortunate enough to have 2 asgts tried other hand unit and cable to eliminate those mine was dec motor.

Edited by germana1 (03/24/11 04:48 PM)


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RobbW
sage


Reged: 02/09/10

Loc: Elgin, IL
Re: RA motor going haywire on a CG5-GT mount new [Re: germana1]
      #4472315 - 03/24/11 11:07 PM

Okay, I finally figured out the problem, and I have to say I'm a little miffed at myself for not realizing it sooner. I'm going to chalk this one up as a newb mistake. Exactly how long do you get to claim newbie staus, anyway?!

Running under the assumption that something was amiss with my AC power adapter, I poured over the internet in search of specs for a proper adapter. Turns out that not only does the adapter need to be 12VAC and have a positive polarity tip about 2.1mm wide, but it also must provide a regulated 1.5 - 2 Amps. It was that last part where I had seriously dropped the ball. I went running down to my mount to check out the adapter I had been using. Sure enough, it was 12V with a positive tip, but it only supplied 400mA.

<<<smack forehead>>> D'oh!!

I quickly proceeded to Radio Shack where I purchased a 12V 2.5A regulated adapter with both a 2.1mm and 2.5mm interchangeable tip (wasn't sure which I needed). Got home, assembled the adapter, plugged it in, and fired up the CG5. Went through the initialization paces, and after a little tweaking, everything is working perfectly. Well, actually, it took quite a bit of tweaking. It turns out that when reassembling my mount following the Hypertune, I had meshed the motor gears too tightly with the worm gears on both axes. The motors were really straining to move the axes, and combined with an insufficient power source, I'm surprised I didn't burn out the whole thing!

So, in the end, everything is working perfectly. And this can be added to the numerous testimonials about the CG5's extreme finickiness for clean, ample power.


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