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Thread: Oh no! Trouble in paradise! Backlash! HELP!!!

  1. #1
    jgroub's Avatar
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    Question Oh no! Trouble in paradise! Backlash! HELP!!!



    After all the praise I've been heaping on my scope lately, now I'm in trouble. The azimuth motors are extremely slow to respond. When I slew the telescope, either left or right (azimuth), it is taking literally 11 seconds to respond to my pressing the button by moving. Either direction, doesn't matter.

    I have the telescope out tonight. It's only 35 degrees, and I had it out in below freezing weather 3 days ago when it was 25, so I don't think it's the temperature.

    Here's when it started: I got a new EP today, the Paradigm Dual ED 15mm. After going through the alignment procedure for the first time, on Vega and Altair, I inputted to goto M29 as a first light test on the new EP. The telescope dutifully moved to the right location. I switched out the 32mm Plossl for the 15mm, which, by the way, gave nice views.

    As I was removing the Paradigm to goto the next object, the "shallow safety groove", as the website calls it, got caught on the set screw, and yanked the telescope up - in altitude. I knew the telescope was out of alignment at this point, so I went to realign. I turned off the power and started fresh. But after realigning on the same two stars, the Goto couldn't find anything. And that's when the lack of response started - but in azimuth, so I don't know if this has anything to do with what's going on. No matter which direction I go, left or right in azimuth, I can count to 11 before the telescope starts to move.

    I thought it must be some kind of backlash problem. So I go into the anti-backlash menu, azimuth. It's still on 0, both positive and negative. I start out with 10 positive and negative. No difference. Okay, I go to 20 on each. No difference. 50? 99? Nothing effects this. I reset them both to 0. Same.

    What do I need to do? HELP!
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  2. #2
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    Default Re: Oh no! Trouble in paradise! Backlash! HELP!!!

    This is not backlash, and the backlash configuration settings will have no impact on this behavior.

    Before the incident with the mount interference, you indicated slow movement/slow response of the telescope to slews in altitude and azimuth.

    This could be either, or both of:

    - power supply problems - are you running on internal batteries, an external 12V supply, or a 12V AC/DC converter?
    - cold temperatures, which affect both hand-controller response, and motor-control, motor/reduction gear motion

    The internal drive uses a combination of plastic and metal spur and pinion gears. Hanging, or binding the mount can damage the teeth on these gears, and result in no motion, or chattering/sporadic motion. It can also cause a gear to spin, or slip on its shaft if the binding was significant enough (this is rare).

    You should set your backlash settings back to their defaults. Make sure your power supply, whatever its source is fresh and fully charged. Test indoors, with the telescope and hand-control warm to room temperature.

    If you have known good power, and the telescope is at room temperature, and these faults persist, you likely damaged the mount.
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    Default Re: Oh no! Trouble in paradise! Backlash! HELP!!!

    By taking the EP out you caused the alt to move manually, the ALT friction clutch just slipped, should be no problem and won't affect the AZ.
    You want it to be tight enough not to slip under normal conditions, but loose enough to slip if the scope hits the mount base or tripod for some reason.
    Underneath the dovetail mount you should see a silver bolt head 12/13mm or so, if you take off that plastic outer cover you can see the nut that tightens the friction on the inside.

    Could be cold, stiff grease and/or low V in the batteries.
    Could be it got dirty and too much friction on the AZ axis.
    Could be the slew setting speed got changed, does the ALT still work at normal speed?
    Could be it's been talking to your other scope, and just wants to mess with ya.

    Do a factory reset, can't hurt.
    I would get a separate rechargeable 12V 8AH AGM or lithium battery pack and a battery charger/tender and not depend on those AA's.
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    Default Re: Oh no! Trouble in paradise! Backlash! HELP!!!

    Certainly sounds like a power related problem. Make sure you are using a fresh set of batteries when you start an observing session. This is especially true in cold weather. Also, rechargeable NiMH AA batteries produce only 1.2 vdc, not 1.5vdc; 8 NiMH AA batteries produce a total of 9.6 vdc instead of the 12vdc needed by the mount.
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    Default Re: Oh no! Trouble in paradise! Backlash! HELP!!!

    First of all, thanks very much to all for all of the information/suggestions. If you couldn't tell, I was practically freaking out when I posted this - and thus the double post. Sorry about that as well.

    It looks like Austin was right on this one, though.

    It was not the power supply. I was running it off of a 12V Lithium pack, this one:

    Amazon.com : Portable DC 12V 4500mAh Rechargeable Li-ion Battery for CCTV Camera Wireless Camera / Baby Monitor, Digital Camera, CD/MD : Baby

    which had just been very freshly charged for about 12 hours before use, light switched from red to green and everything. Plus, I had a full supply of 8 relatively fresh Duracell AA Alkalines hooked up in the tank as well, as backups - not rechargeables, the real deal. The same motor delayed reaction thing happened with both power supplies.

    And it's not a temperature problem, either. Same thing happened once I got the scope inside and it had warmed up. In fact, the azimuth motor does sound different now, so, yup, it has to be the pulling out of the EP that did it.

    Along those lines, just as a slight correction to what Austin posted, however, which is that this all started AFTER the mount interference with pulling out the Paradigm, and it getting caught and pulling up the back of the scope. Immediately after, because once I did that, I knew the scope was out of alignment. So I shut down, realigned, and then couldn't get any object into the scope, while at the same time I couldn't move in azimuth without the very long delay.

    Strange as it may seem, Hilbily, it appears that the effect of yanking up on the altitude motor while tracking was engaged caused a problem with the azimuth motor. I would agree from a logical perspective that this makes absolutely no sense, because I know, as you mentioned, that the altitude has a clutch, and, as you also mentioned, that the altitude still works perfectly normally, moves up and down immediately. But still, here I am. And I don't think it "got dirty" - I've only been using the scope for two weeks, and although my bedroom isn't exactly a NASA clean room , it's not as if I had opened the motor up and exposed it to toxic sludge, either. And your comment about my two scopes talking to each other was mean-spirited. But hilarious! Really put a smile on this freaked out face. Thanks for the levity!

    However, I will leave it to Celestron to puzzle this one out, however, because back to Amazon it goes for an exchange. I still like the scope; now I know I just have to treat it like an egg, instead of a tank.

    Once again, thanks for the responses, guys. But I do have ONE THING to say - this should not happen. It's not as if I cavalierly yanked the EP out of the diagonal. I pulled on it the way I normally pull any EP out, and the back of the scope moved maybe 5 degrees up when I did so. For something as simple as this to completely screw up the motors is very poor (and probably cheap) design. Rant over.
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    Default Re: Oh no! Trouble in paradise! Backlash! HELP!!!

    For another example of telescope poor design, how about the new Dobsonians that we buy for a significant price, that come with mirror collimation springs that can't support the mirror steadily! Ridiculous!
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    Default Re: Oh no! Trouble in paradise! Backlash! HELP!!!

    Quote Originally Posted by stargazer55 View Post
    For another example of telescope poor design, how about the new Dobsonians that we buy for a significant price, that come with mirror collimation springs that can't support the mirror steadily! Ridiculous!
    One of the many reasons that I bought a telescope - a Mak - that doesn't need collimation.

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    Default Re: Oh no! Trouble in paradise! Backlash! HELP!!!

    That's weird, I thought you could only damage the scope by moving it horizontally (which would require a lot of force based on what I can see). I've taken my scope to several public viewing/outreach events and have had kids yank on it, knock it out of alignment, et cetera, and I don't think I've ever had a problem with the tracking or any other issues (besides having to realign it and telling apologetic/mortified parents it was no big problem). Did you update the firmware? I guess its a moot point now, hope you get a response back soon.
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    Default Re: Oh no! Trouble in paradise! Backlash! HELP!!!

    Quote Originally Posted by Diogenes View Post
    That's weird, I thought you could only damage the scope by moving it horizontally (which would require a lot of force based on what I can see). I've taken my scope to several public viewing/outreach events and have had kids yank on it, knock it out of alignment, et cetera, and I don't think I've ever had a problem with the tracking or any other issues (besides having to realign it and telling apologetic/mortified parents it was no big problem). Did you update the firmware? I guess its a moot point now, hope you get a response back soon.
    Yeah, it was vertically, not horizontally - I pulled the EP out straight up, and the back of the scope moved up with it.

    I agree that this doesn't make any logical sense in that what I did in altitude would cause anything to go wrong in azimuth. And maybe it didn't- maybe that motor just went right at that moment. But the timing sure is suspicious. It WAS working right up until that moment.

    No, I didn't update the firmware, because it was a pretty current version - 5.21, I think - and I didn't see the need because the scope was working fine. Now the motor sounds off in azimuth, but in azimuth only.

    The way the return at Amazon works is they send me a new one - which will arrive Monday! - and then I send back the old one. Pretty nice of them.

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    Default Re: Oh no! Trouble in paradise! Backlash! HELP!!!

    Oh good, I think Monday may be the only clear day we get all week here, unfortunately. It'll be warmer too, though I don't think the folks in Buffalo would appreciate that much. Hope the new scope works out better for you.
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