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Celestron AVX mount - How to fix tight RA / Dec axis


ChrisEll
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Here's a quick guide to adjusting the tightness on the Dec and RA axes on the AVX mount. Freeing up the axes means better guiding, less wear on gears and motors (some gears in the drivetrain are plastic), lower worm PE and you will be able to balance more precisely.

Dec axis: 

Remove the counterweight bar and cup to reveal the tension ring. To adjust this first loosen the 2 grub screws at its side... there is a small access hole at the side of the housing. You'll need a tiny allen key to do this. Then use a slightly larger, stiffer allen key and insert this into the access hole and against the grub screw so that the tension ring is wedged tight against the allen key - this serves to hold the tension ring in place as you turn the axis, no need for a special tool! Now rotate the mount saddle anti-clockwise to loosen the tension ring until you feel some vertical play (grab hold of the saddle and move up and and down to test). Slowly tighten until there's no play. Tighten grub screws.

RA axis: 

Remove the plastic cup at the end of the axis. The RA tension ring has 3 grub screws and the access hole is hidden by the control panel cover (3 screws hold this in place). My RA axis was very tight and needed a few turns of the axis before I got any vertical play.

For those wishing to improve their AVX further I recommend adjusting the worm housings in both axes.

Dec_tension_ring.JPG

RA_tension_ring.JPG

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I posted some info about AVX disassembly before but this seems like a good thread to add them again. 

http://rocketsparrow.blogspot.co.uk/2017/01/how-i-made-better-celestron-avx.html (note the comments at the bottom about removing the RA tensioner there are 3 grub screws to loosen first  and it needs a very small allen key as shown above)

https://www.flickr.com/photos/10605262@N04/sets/72157646742806679/?ytcheck=1

This guide is for the older but similar CG5  http://astronomyboy.com/cg5/

https://www.cloudynights.com/topic/578878-celestron-avx-rebuild/

I replaced the RA bearing with an angle bearing  although it does leave a slight gap as mentioned in some threads but it made a HUGE difference to RA stiction

http://www.ebay.co.uk/itm/SKF-32007XQ-Metric-Single-Row-Taper-Roller-Bearing-35x62x18mm/130940248658?hash=item1e7ca5a252:m:m3AAqpQNFsFJgnN6vqioQOw

It's easier than I thought I didn't even need to remove the RA from the mount part.

It certainly made things less sticky and balancing became a lot easier although guiding performance wasn't much better. 

 

In the end I bought an EQ6-R which has been a massive improvement. 

Rob.

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  • 1 year later...

I just wanted to say thank you. My DEC axis was pretty stiff and I never felt confident that I was balanced properly. It's worlds better now and much easier to balance.

 

Thank you!

Edited by ELEMENT22
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  • 9 months later...

Thanks for replying Chris. 

One more thing, when loosening the RA axis should I follow the same method of rotation (anticlockwise) then pull/push then adjust so that there is no play then tighten the grub screws? 

Just an insight, Iam a newbie to astronomy but very passionate about seeing this through. Also just recently tried astrophotography and I can safely say iam addicted! I was warned about the Avx mount but chose not to listen. Appreciate all the help though on anything to help make guiding smoother. 

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38 minutes ago, Astrowal said:

Thanks for replying Chris. 

One more thing, when loosening the RA axis should I follow the same method of rotation (anticlockwise) then pull/push then adjust so that there is no play then tighten the grub screws? 

Just an insight, Iam a newbie to astronomy but very passionate about seeing this through. Also just recently tried astrophotography and I can safely say iam addicted! I was warned about the Avx mount but chose not to listen. Appreciate all the help though on anything to help make guiding smoother. 

That sounds fine to me.

Yes I got addicted to imaging but now finished my journey.

The AVX is capable of good results, just needs some tweaking which is probably true of all of the cheaper GOTO mounts.

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For the most part it's been pretty accurate visually. I do have a Celestron 9.25 sct attached to it. Could be the weight of the scope that's throwing it off for astrophotography. 

It is quite stiff though, so stiff that I could balance it with my eyes closed. 

 

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13 minutes ago, Astrowal said:

For the most part it's been pretty accurate visually. I do have a Celestron 9.25 sct attached to it. Could be the weight of the scope that's throwing it off for astrophotography. 

It is quite stiff though, so stiff that I could balance it with my eyes closed. 

 

That's a big scope for imaging on the AVX... I had a 8" SCT and it was a struggle! I then got a SW ED80 refractor which was an improvement, being lighter and having a shorter focal length.

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Iam actually looking into a smaller refractor to mount on the Avx. Was told the 9.25 was a bit on heavier side for the Avx, at that point though I was just interested in visual only. Guess I am gonna have to pay the price. 

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Hi Chris, I just have to thank you again, I managed to do the tweaks and it's just so much better, a massive improvement compared to its previous state. Gonna give guiding a try tonight, hopefully register some improvements in that area as well. 

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