Celestron AVX Mount Problems: How to deal with backlash
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- เผยแพร่เมื่อ 16 ก.ค. 2024
- Hi Folks,
The Celestron Advanced VX + polar axis finder is available at Amazon: amzn.to/2qwCmCh
I noticed a lot of backlash in PHD guiding lately. In this video i check out and re-adjust the motors of the RA and DEC axis of the AVX and put some new grease on the wheels. I hope this will help fight my backlash issues. If not, I have to buy a new mount :-). Anyway, hope this is helpful.
link to my zwo asi 1600mm pro camera:
amzn.to/2ubpFyW
link to my Celestron Advanced VX mount:
amzn.to/2NkqrjQ
You can also find me here:
Website:
www.astroforumspace.com/
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/ astroforum
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Celestron AVX mount link: amzn.to/2qwCmCh
Its worth noting that one of the two allen screws must be on the flat part of the motor shaft so it wont move over time.
Thanks for the video. Also, make sure the gear set screw is lined up on the shaft flat or else the gear could spin on the shaft
Weather... I'm in the UK.. I feel your pain. Good video. Just been trying out my new ZWOASI178 ( thanks for your video on ZWO btw) First clear night saved as RAW monochrome by mistake.. second clear night recorded tantilising images of M1, M51 Eskimo Neb M42, third night being an idiot deleted all my images by mistake whilst deleting large video file.. now cloudy lol.. still learning. I love your channel so helful
Great tips. Thanks for sharing!
Just followed your instructions and it was so easy! I can't test it tonight but with the amount of slop I was seeing in the gears that would seem to correlate to my bad guiding in PHD2. Thanks for your time!
Great, hope it will help you guide better! If not, an extra procedure can be to nail your polar alignment...I'm thinking about making a video on this, but the weather in the Netherlands so far s**ks :-).
@@AstroForumSpace My PA is pretty darn good. I have the PoleMaster and it is easy and awesome :) The backlash issue has creeped up because I started using NINA, a sequencer program, and Dithering. With Dithering enabled the mount is unable to recover from the backlash and my guiding goes to heck...
@@AstroForumSpace I posted about your video and my following of it on The Sky Searchers Forum: www.theskysearchers.com/viewtopic.php?f=24&t=2890 bobharmony replied with this and I was curious if you knew about the second part he is referencing?
"Nice job on digging into the gear mesh. Getting the motor gear and the worm gear is half the battle. There is another adjustment that can be made with the plastic covers off that our friend in the video didn't do.
The worm gear that he refers to meshes with a cylinder attached to the axis itself to actually rotate the mount. if you look closely at the video you will see three allen bolts in a row underneath the dec motor. Those can be used to adjust the fit of the worm gear to the teeth on the cylinder. If I recall correctly, the two outside bolts are there to hold things in place, and the center bolt controls the spacing. When the center bolt is loosened it will allow the worm to mesh more tightly to the teeth, and if you tighten the center bolt it will create more space between the worm and the teeth.
The idea is to loosen the two outer bolts, make a small adjustment to the center bolt, then snug the outside bolts again. Run the motor through as much of a turn as you can. The idea is to get the mesh tight without making it so tight that it binds at any point in the rotation. It may take several iterations to get the setting just where you want it.
Oh, and when you are done with the worm adjustment, go back and do the motor gear-worm gear adjustment again, as doing the worm adjustment will affect the relative position of the motor and worm gear
About the plastic covers, yeah they are a pain to get back on, and I have managed to strip the screw threads on at least one of the connections points. Go gently with those too!
Bob"
Thanks for sharing my video :-). And yes, that's a second option. I didn't try that one. If the guiding continues to be poor that could definitely be an interesting adjustment. Clear skies!
@@AstroForumSpace did your guiding get better after doing this tune-up? My phd2 keeps saying there's little to no south movement on my mount. I also have a Avx. I can't make it guide for the life of me.
Hi, hope your mount works nicely and that the weather improved ;)
Nice video, just a though on the allen set screws on the spur gear on the motor.
One of them should be on the flat part on the axis normally. Might start slipping if there is a big change in temperature.
Clear skies
Hi astroboden, Actually, I think this has happened. My phd2 guiding is showing a huge backlash in DEC. Do you have some resources, links or literature so I can understand what tot do :-)?
@@AstroForumSpace What does phd2 guiding assistant tell you? Does it have problem with inconstant movement? How much is “huge”? And does it handle it with backlash corrections?
Can you introduce a (small) polar alignment error and then guide in only one direction? You can also balance against the guide motion (same side as the drift) to get the same balance assist as one get when east balancing RA.
@@astroboden I get a message every time I calibrate that it detects a Dec backlash. Guiding works but it takes a couple of seconds before I see Dec corrections. My guiding error is between 1 or 2 arcseconds depending on the night. not too bad for an AVX but I think I can do better.
@@AstroForumSpace That sounds pretty good then. Some backlash is unavoidable, it's worse with binding! We just have to work around it.
Just make sure the "backlash compensation" checkbox is checked. I found that sometimes it's unchecked. Then it takes some time for corrections to come in.
@@astroboden yes, backlash compensation is checked, thanks for the tip!
As usual, good work and thanks for the advice. You have taken out the baklash in the dec spur gears, did you also do the RA? Did you look at tuniing out any backlash in the worms or was it only the spur gears? Thanks, Gary
thanks Gary. I did ra and dec, i adjusted the gears so that they are closer to the worm and put grease on the wheels. I did not adjust the worm in any way, thanks voor the tip! I also perform a polar alignment procedure using sharpcap, this also helps.
@@AstroForumSpace Hi :) Can you tell me more please how you did your polar alignment using sharpcap? Sharpcap is the camera utility, right?
@@HollomanUFOLanding check the end of this video: th-cam.com/video/XqcbDC3pdG0/w-d-xo.html
Why loosen the Allen screws holding the motor gear to the worm gears? Just loosen the screws on the motor bracket and position it either into or out of the corresponding worm gear. Depending on local weather conditions and time of year, you may have to readjust the gear mesh, especially in cold weather
the weather is like that for months here in the pacific northwest.
Music is deleted
So how did it go? Hope you've had a clear night. From what I know, there should be a little bit of backlash between the gears.
Yes, I left some room between the wheel and the worm. Guiding on the Dec axis improved considerably, RA was similar. Could also be due to settings in phd2.
@@AstroForumSpace good to hear. are you able to guide Dec in both directions now? On my AVX, I have to guide only in one direction due to backlash
@@anthonysaab1186 yes, auto on phd guides dec in both directions.
Before you did this was PHD saying the dec backlash was to big to detect movement when you were trying to run calibration? That's driving me crazy and the help page from PHD seems to think the mount is bad. It's only 3 months old or so. I'm about to try to fix it with new lube, and adjusting the motor(s) to see if that clears up. I think the RA is fine but maybe some new lube will help the stickiness.
For me, it helped a bit. I also began to use sharpcap polar alignment procedure, and that really helped to bring down the periodic error.
I’ve been looking into purchasing this mount, what’s the average guiding error you get on this mount?
With guiding and pec tool on I get sub arc second accuracy. Note that I work with a small refractor. Avx can guide well below about 10kg. If you need more the cgem is a better choise but less mobile. Hope you find what you're looking for!
@@AstroForumSpace I’m using a small refractor but I’ve been getting bad performance issues. Hoping this video will help me out!
I was able to test everything out last night. As stated in my other post I did this because of bad DEC guiding in PHD2. Brian on the PHD2 forum has been reading my logs and helping me out. Here's what he had to say after following your instructions on Backlash (groups.google.com/forum/?#!topic/open-phd-guiding/WO5RlysRICU):
"here's the good news - you crushed it on improving DEC. if i hack out the parts of your poor guide stars (presumably branches, etc.) DEC is significantly better
here's the bad news - you crushed it on improving DEC, so much that now your RA is more of the limiting factor!
you just can't win right? :)
But i'd say you did a great job taming that, well done...
" He goes on to say I should try PEC, which I'll do next.
Thanks once again for the great video! Made my day that I not only didn't screw anything up, but actually did pretty well with my adjustments :)
Good to hear, and taming RA is indeed my main goal. PEC tool helps a bit :-)
would be nice if celestron provided an adjustment screw rather than just mounting screws... that would make such corrections to gearing much easier...
thanks for the video, with a little luck it will help me correct my declination backlash error.
What is backlash and what does it do to the mount?
The wheels are a bit too far apart of the motor, so it takes a while for the mount to change its position. You don't want that as the tracking of objects become inaccurate.
The only issue is to put lubrication on the bearing and wheels
Please don’t tilt your camera. Just film parallel to the horizon.
Thanks for the tip, but if possible remove the background music.
Thanks! I was experimenting with TH-cam studio,, I'll delete it tonight :-)
Its been a nightmare buying parts like polar scopes and counterweights at the moment.. even my due shield I had to make myself. Probably Brexit or Corona Virus
P 10 of the AVX manual says the mount does not track in Declination, only in Right Ascension. So any modification to the Declination gears won't many any improvement to tracking. If you were having problems with tracking, did you submit a ticket to the manufacturer?
Hi claude, no, i did not contact celestron because my avx was already guiding within 2 arc seconds when also guiding. Recalibrating the ra and dec motorwheels and by improving my polar alignment, i got my guiding accuracy down to sub arc second for ra and dec which allows me to make multiple minute images with pinpoint stars.
Guiding/tracking in dec on an equitorial mount? Equitorial mounts only track in ra, not dec. That's the whole point of an equitorial mount. Sub arc sec for ra? RA is measured in h, m, and s. Dec (or angular separation) is measured in degrees, arc minutes, and arc seconds. You may want to take out the AVX owner's manual and refer to the TIP on p. 10 for optimizing tracking accuracy. Also, th-cam.com/video/ZKnms9GhM6Q/w-d-xo.html has some good pointers on balancing, especially east bias balancing to minimize, if not eliminate, gear backlash.
@@claude77573 sub-arc-second would imply increments of less than one arc-second... the world is analog, not digital.
@@claude77573 even slight errors in polar alignment will result in a need to correct declination as the mount tracks from east to west... this is a simple geometry problem that you could verify for yourself with pen and paper... you might also want to take a look at phd2/phd guiding and note that it does indeed make declination corrections... the mount might not track in declination, but programs that make corrections for guiding with pinpoint accuracy of less than an arc-second do.
@@idiotsnightmare Thank you for responding to my comments. You are a good man! Based on your video, I decided to go ahead and buy and AVX mount, and I'm glad I did! I also apologize for being a jerk. I should know better.
I can barelly hear you..the music is so loud
I'm deleting the music and I'm re-uploading, should be gone one hour from now.
Hoi Wido, ik krijg deze mount ook, zijn daar nog nog onderdelen van te koop ?
Volgens mij wel. Ganymedes verkoopt de avx nog steeds.