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German Equatorial Mount - Need More Information Please.


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#1 jiangshi

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Posted 14 September 2015 - 09:52 AM

Dear Meade,

 

Below is a picture of the German Equatorial mount that comes with my Meade Polaris 130 telescope.

 

EqMntRedArrows.jpg

 

Starting from the left side of the picture, the first red arrow (1) is pointing to a large allen screw. What does this allen screw do/adjust?

 

Red arrow 2 is pointing to an indicator, and to the right of the indicator is a thumb screw. I know that the thumb screw must be loosened in order to set the RA as pointed to by the big RA painted in white of the top of the gear housing. I know how to use basic setting circles, but what is this little silver pointer for, and how is it used?

 

The third red arrow is pointing to a recessed small allen screw. What does this allen screw do/adjust?

 

I am asking these questions because I want to know about my mount. Secondly, when the scope is all put together and balanced, the worm gear for the RA is too stiff.

 

Thank you!

 



#2 MistrBadgr

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Posted 14 September 2015 - 03:23 PM

I am not sure about the set screw at arrow 3 (other than it might be holding a bushing in place) or the item for arrow 1 (I don't have even a guess there!)

As for arrow 2, I have never used setting circles, so I am as complete a novice as you. I do have my Polaris 130 with me and have looked it over. The only thing I see with the pointer is that the scope is aimed at the meridian (the line that goes from the South Celestial Pole, overhead, to the North Celestial Pole) assuming the RA axis is aligned with the appropriate pole.

As far as the RA drive being too tight, look at the end of the shaft on the side of the silvery gear. There is a keeper nut that has squarish notches in it. I think you can loosen that keeper nut a bit, then turn the portion or shaft that is sticking out of the keeper nut. I think it is attached to the threads of the bushing that stick inward from the black piece of metal that is part of the housing. I believe there is a tapered setup on the shaft inside this bushing piece that the bushing pushes against. I think that you can loosen that a tiny bit and relieve the tightness you feel. Be sure and re-tighten the keeper nut. If that does not loosen it up or things get to feeling sloppy, holler back and I will see if I can get someone else involved.

On an Infinity 102 that I have, there was a little fragment of machined material that had stuck inside of the equivalent place, that I had to get out and then simply grind the thing back and forth until the surface smoothed up a bit, but hopefully yours is just a bit tight.

Let me know if this does not work or does not make sense.

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

#3 Mark Sibole

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Posted 15 September 2015 - 07:38 PM

Try checking if there is any info in the owners manual first.From the looks of it 1 would be a tension screw for the ra and 1 would be a set screw to lock the ra serring circle in place.Not sure on the other one.I dont have a manual on this mount so im speculating from other mounts Ive owned.


Mark Sibole
MTSO Observatory
Fife Lake, Mi.

http://astronomy.qteaser.com

#4 jiangshi

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Posted 15 September 2015 - 11:36 PM

Try checking if there is any info in the owners manual first.From the looks of it 1 would be a tension screw for the ra and 1 would be a set screw to lock the ra serring circle in place.Not sure on the other one.I dont have a manual on this mount so im speculating from other mounts Ive owned.

 

HI Mark,

 

I checked the user's manual and looked around online before taking the pic and posting my question here. I was hoping that Meade had access to the service manual for the mount. However, what you are saying about 1 being the ra tension makes sense and is easy to check out. I think Bill is correct about 3 being a set screw for holding a bushing and is probably used only in disassembling the mount. I am guessing that the little pointer must be for setting some offset to the ra, since the ra setting circle and pointer turn together.

 

Thank you for your comment.

~todd



#5 jiangshi

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Posted 16 September 2015 - 12:44 AM

As far as the RA drive being too tight, look at the end of the shaft on the side of the silvery gear.

 

HI Bill, I think I have the ra tightness issue solved. I tried the shaft adjustment first, as you suggested, but it seems to be properly centered and not binding anywhere. However, the whole worm gear assembly is held onto its mount by two bolts underneath the worm gear assembly. I loosened the bolts and re-centered the worm gear on the driven ring gear, and that seems to have eased the tightness. I'm guessing that the worm gear teeth were engaging into the driven gear teeth too deeply and causing some binding. I'm thinking that the adjustment is kind of a happy medium between too much gear backlash and too much gear tension. Either one could cause premature gear wear. Anyway, it is moving much more freely now, so we'll see how well it goes under full weight load next time I take the scope out.

 

~todd






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