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Meade Polaris 90: making precision controls go smoother


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#1 Andrey

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Posted 24 July 2018 - 02:09 AM

Greetings, dear Meade users!

 

  I am a newbie owner of Meade Polaris 90 with German equatorial mount.

  After one month of happy sky watching I noticed that rotation of declination and right ascension control cables feels not smooth, but with tension and scratching sound. In the result in an ocular I observe jumps instead of smooth motion.

 

  Would you be so kind as to suggest me a way to untie precision controls and/or put additional grease?

  What grease do we normally use for Meade German equatorial mounts?

 

  Thank you for a detailed reply.

 



#2 MistrBadgr

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Posted 24 July 2018 - 02:33 PM

Hi Andrey!

 

I do not have one of the Polaris refractors, but I do have all three of the reflectors.  I will look over one of my mounts and get back with you on how to get into it.  In order to keep the price down, they do make these things in a hurry.  I have found one of the infinity mounts in the early days of that line that had some metal shavings inside the action that made it act about like you are describing.  I was able to pull it apart, clean out the metal particles, and regrease with some medium grease.  It worked very well after that.  I will try to look it over and get back with you, hopefully tomorrow.

 

I have to go and work in some hot places on a steam boiler tomorrow and am not sure how well my mind will be working after that.  If I am not thinking clearly, I will wait until I have rested to answer.

 

If you live in the United States, and your scope is still under warranty, you can call Meade at 800-626-3233.  In other countries, the rules and contracts with suppliers vary.  Therefore, I cannot speak to arrangements for a replacement under warranty.

 

I will report back to you after I have looked over one of my mounts.

 

Also, I hope to answer your other post soon.  I want to think about your questions a bit before I answer.

 

Best Regards,

 

Bill


  • RickScofield likes this
Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#3 Andrey

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Posted 24 July 2018 - 10:45 PM

Dear Bill,

 

  Thank you.

  I will wait for the answer as long as required.



#4 MistrBadgr

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Posted 28 July 2018 - 07:37 PM

Hi Andrey,

 

On your Declination control, I think I have an answer.  I took one of mine apart to see how it is made.  On the end with the control knob, the shaft runs through a nut and screws in and out as you turn the knob.  This pushes on a lever that moves the scope around compared to the position of the base of the mount.  As you unscrew this rod with your knob, the other side has a spring loaded shaft (a tube actually) that pushes the lever up against the control shaft, moving the scope back.

 

I found that as I screwed the control rod in nearly to its limit, I did hear some squeaking in  the threads.  The rod does need to be greased enough to keep that squeak from happening.  I believe that squeak is a sign of potential wear in those threads.

 

The side with the spring in it is where I think the problem you are experiencing is happening.  If you look on the end of the Declination mechanism, away from the control knob, you will see a long chromed object that has six sides on part of it for using a wrench.  This is what I will call a "can."  It holds one end of a coil spring and allows a piece of tubing to move in and out that contains the other end of the spring.  The outer, solid end of this tube is what pushes up against the lever, opposite the control knob's rod.  I think the coil spring is catching on the inside edge of that tubing.  I could hear the spring doing that in mine, but not enough to provide a jerk in the motion of the control mechanism.  I plan on using a small, round hobby file to bevel that inside edge that is catching the loops of the coil spring and then re-grease the spring.

 

Putting the spring mechanism back in place took a little effort of figure out.  The lever that moves the scope needs to be all the way toward the control knob, so that control rod needs to be screwed out as far as it can.  I had to take the scope off, take the mount off the tripod, and remove the RA set screw to make room to get my thumb in the right place to guide the parts.  With the spring inserted into the tube on one end, and the "can" piece on the other, just no pressure on anything, some of the spring is still exposed. I held the mount upside down, so that I could see the parts inside the mount.  I stuck the whole spring assembly in, pressed inward on the can and started screwing it into its threaded hole in the framework.  As the pressure increased, the spring wanted to warp sideways and move the tubing  away from the end of the "can" piece.  I screwed in the Can until it started touching the tube piece, then moved the tube around until it was in a position to go into the hole in the can.  I would then screw in the can a bit more, adjust the tubing, and tighten a bit more.  It took maybe three times of these little moves until the tubing went on down into the can and I could finish screwing it into the framework.

 

When I take mine apart to fix the inside edge of the tube the spring fits into, I may also bevel the outside edge to allow it to slide into the "can" easier.

 

A note about grease:  Grease with either graphite or molybdenum sulfide in it will leave black spots on light colored bed spreads and make mama very unhappy. Plain medium grease that you can buy in a tube should work well for this function.  Grease with teflon in it or maybe lithium oxide, if you can find it, would be better.  These extra ingredients are white and to not seem to stick in fabrics as much as the black materials do!

 

I have not figured out anything on the R.A. control yet, but hope to do so soon.

 

If I have not made much sense and you have trouble understanding what I am talking about, let me know and I will try again.

 

Hope this helps,

 

Bill


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Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#5 Andrey

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Posted 01 August 2018 - 03:36 AM

Dear Bill,

 

  I left my house for several months, but I will post the feedback as soon as return.

  Can you upload several photos of dismount process please?






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