How do you deal with AVX backlash?

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Baskevo
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How do you deal with AVX backlash?

#1

Post by Baskevo »


Whats up everyone!

I've been told on the PHD2 forums that I have really bad backlash with my AVX mount. I was wondering if anyone had any suggestions for improving it.

There's a guy in my area who does collimations, setups, etc. and he lists backlash adjustment. Should I do something like that?
I've also heard people talk about period error correction, some people recommend it and others don't?

What did you all do to help with the backlash, or to improve guiding with your AVX mount? I know the AVX is entry level for AP, but I'm hoping there are still things I can do to get better results while guiding.

Thanks all! Clear skies.
-James W.

Telescope: Explore Scientific 80mm FCD100 Triplet APO Refractor
Mount: EQ6-R Pro
Cameras: ZWO ASI1600mm Pro (Cooled) | Canon DSLR EOS T7i
Auto-guiding: ZWO ASI120mm-Mini + Astromania 50mm Guidescope

Filters: ZWO 31mm Ha/Oiii/Sii 7nm + LRGB | Orion 2" Skyglow Filter
Accessories: Explore Scientific 2" Field Flattener, ZWO EFW 8 Position
Software: APT, SharpCap Pro, PHD2, CPWI | PixInsight, DeepSkyStacker, Photoshop

Flickr: https://www.flickr.com/gp/186194203@N06/18B629
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fatboy1271
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Re: How do you deal with AVX backlash?

#2

Post by fatboy1271 »


Hey Baskevo,

I have a post on this: https://www.theskysearchers.com/viewtop ... =24&t=2890

Specifically the fourth post down I link a video from AstroForum. Check it out and it was quite easy. Also, you can read about the help that I got from the PHD2 forum:
https://groups.google.com/forum/#!searc ... UxkKjjAQAJ

fat
OTAs: Explore Scientific ED80 Essential Edition / The Little Guy (Celestron 90SLT)
Mount: Celestron Advanced VX
Gear: Canon 70D / Hutech LPS-D1-48 / ES 2" Field Flattener / QHY PoleMaster / Celestron GPS / ZWO ASI120MC / Orion 50mm Guide Scope / ZWO EAF
Software: CPWI / PHD2 / N.I.N.A / Stellarium/StellariumScope/Remote Control / PI / RegiStax 6 / AutoStakkert!2 / PIPP | Retired? BackyardEOS Premium
EPs: Stock Celestron 9mm and 24mm / Celestron Omni 32mm (I love this one!) / Celestron X-Cel LX 3x Barlow (I think 2X would have been smarter...)
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Juno16 United States of America
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Re: How do you deal with AVX backlash?

#3

Post by Juno16 »


Hi Baskevo,

I think it’s pretty common for an AVX to have a ton of backlash.

You can try tightening up the gear mesh, but for me, I just really try to get a very good polar alignment.
With a good PA, your DEC will not have to be corrected very often and when it does, it won’t be off enough to make a significant difference by the time PHD2 gets control.
Heck, my RA guiding error is always higher than my DEC error and I have a ton of backlash.

You can also adjust the anti backlash settings in the mount HC. I believe the procedure is in the mount manual.

Thanks,
Jim
Jim

Scopes: Explore Scientific ED102 APO, Sharpstar 61 EDPH II APO, Samyang 135 F2 (still on the Nikon).
Mount: Skywatcher HEQ5 Pro with Rowan Belt Mod
Stuff: ASI EAF Focus Motor (x2), Orion 50mm Guide Scope, ZWO 30 mm Guide Scope, ASI 220mm min, ASI 120mm mini, Stellarview 0.8 FR/FF, Sharpstar 0.8 FR/FF, Mele Overloock 3C.
Camera/Filters/Software: ASI 533 mc pro, ASI 120mm mini, Orion SSAG, IDAS LPS D-1, Optolong L-Enhance, ZWO UV/IR Cut, N.I.N.A., Green Swamp Server, PHD2, Adobe Photoshop CC, Pixinsight.
Dog and best bud: Jack
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My Astrobin: https://www.astrobin.com/users/Juno16/
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Baskevo
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Re: How do you deal with AVX backlash?

#4

Post by Baskevo »


Thanks for sharing, Fatboy! I was looking at that video, but I'm scared to try it... I'm going to bookmark it and keep it handy, just in case.

I think my guiding is actually pretty good. This is what I got from Andy at PHD2:

I took a look at your latest log. You're getting decent calibrations and the guiding is not bad. From about 1:21 to about 1:30 (before the sky conditions were deteriorating) you were getting about 1 arc-second guide error which is not bad at all, about at the limit of what the mount can deliver. The key to that result was that there was a small amount dec drift from the polar alignment offset, enough to keep the dec axis corrections always going south. This avoided the problems with the mount's dec backlash (the dec axis cannot easily handle changing direction of dec corrections.) So to answer your question about drift alignment I would say sure, you can try it but be aware that tuning your polar alignment below 5-6 arc-minutes error will almost certainly make your guiding worse.

You can ask in a mount-specific forum to see if your dec backlash can be tuned, but be careful not to go too far and introduce binding in the dec axis which is worse than just backlash.


I think I understand the CCD suitability calculator now that @JayTee shared with me lol and if I'm not wrong, I'm getting some pretty good results for the AVX!
I was able to get this shot last night before the clouds rolled in. This is a single sub at 300 sec:
Screen Shot 2019-09-27 at 2.11.32 AM.png
I was having a terrible time with dew... But my stars look great! I'm going to try to repeat what I did last night and hope for the same results. If the DEC backlash causes me too many problems, I'll consider doing it.

I do have 2 questions though:
1) What kind of grease did you use? The guy in the video uses the lithium grease, and I heard that's not that good to use, and that superlube or bicycle grease is better.

And 2) If you know, do you think it would be a good idea to look at PEC before adjusting the backlash, or after? Just in case the other night was a fluke and I do have to improve my backlash.

Thanks again, Fatboy and Jim! I appreciate it.
-James W.

Telescope: Explore Scientific 80mm FCD100 Triplet APO Refractor
Mount: EQ6-R Pro
Cameras: ZWO ASI1600mm Pro (Cooled) | Canon DSLR EOS T7i
Auto-guiding: ZWO ASI120mm-Mini + Astromania 50mm Guidescope

Filters: ZWO 31mm Ha/Oiii/Sii 7nm + LRGB | Orion 2" Skyglow Filter
Accessories: Explore Scientific 2" Field Flattener, ZWO EFW 8 Position
Software: APT, SharpCap Pro, PHD2, CPWI | PixInsight, DeepSkyStacker, Photoshop

Flickr: https://www.flickr.com/gp/186194203@N06/18B629
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Juno16 United States of America
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Re: How do you deal with AVX backlash?

#5

Post by Juno16 »


Hi Baskevo,

PEC and backlash in DEc are different. PEC is a method of attempting to correct regular long oscillations in the RA axis.

I have both issues and my stars aren’t that bad. At least good enough for me.

For me at least, if it ain’t broke, don’t fix it! Yet anyway.

Thanks,
Jim
Jim

Scopes: Explore Scientific ED102 APO, Sharpstar 61 EDPH II APO, Samyang 135 F2 (still on the Nikon).
Mount: Skywatcher HEQ5 Pro with Rowan Belt Mod
Stuff: ASI EAF Focus Motor (x2), Orion 50mm Guide Scope, ZWO 30 mm Guide Scope, ASI 220mm min, ASI 120mm mini, Stellarview 0.8 FR/FF, Sharpstar 0.8 FR/FF, Mele Overloock 3C.
Camera/Filters/Software: ASI 533 mc pro, ASI 120mm mini, Orion SSAG, IDAS LPS D-1, Optolong L-Enhance, ZWO UV/IR Cut, N.I.N.A., Green Swamp Server, PHD2, Adobe Photoshop CC, Pixinsight.
Dog and best bud: Jack
Sky: Bortle 6-7
My Astrobin: https://www.astrobin.com/users/Juno16/
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yobbo89 Australia
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Re: How do you deal with AVX backlash?

#6

Post by yobbo89 »


i'm using nulon l80 lithium ptfe with no problems. their are slightly better products i could try,but it's enough for my guiding, i think some manufacturers recommend a type of grease, end results is you would get a very slightly smoother guiding oscillations on the small end with better grease. manually adjust the meshing is going to be the big improvement , ultimately ditching the gear cogs to the worm will be alot better but i don't think anyone sells a belt mod for an avx and i'm pretty sure you have to wire the motors in reverse , it's not as easy as an eq6 which has 3 cogs



someone did a belt mod but it's mostly likely custom of the shelf parts,ie not sold as a kit


i can't find any info on worm adjustment it looks the whole gear system might be all inline , because the gear cog is on the worm, if you were to adjust the gear worm it would adjust the meshing of the motor as well. so i'm guessing if you want to tune the mounts worm to the main hobed out gear you then would have to go back and re adjust the small gears at the motor after
scopes :gso/bintel f4 12"truss tube, bresser messier ar127s /skywatcher 10'' dob,meade 12'' f10 lx200 sct
cameras : asi 1600mm-c/asi1600mm-c,asi120mc,prostar lp guidecam, nikkon d60, sony a7,asi 290 mm
mounts : eq6 pro/eq8/mesu 200 v2
filters : 2'' astronomik lp/badder lrgb h-a,sII,oIII,h-b,Baader Solar Continuum, chroma 3nm ha,sii,oiii,nii,rgb,lowglow,uv/ir,Thousand Oaks Solar Filter,1.25'' #47 violet,pro planet 742 ir,pro planet 807 ir,pro planet 642 bp ir.
extras : skywatcher f4 aplanatic cc, Baader MPCC MKIII Coma Corrector,Orion Field Flattener,zwo 1.25''adc.starlight maxi 2" 9x filter wheel,tele vue 2x barlow .

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yobbo89 Australia
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Re: How do you deal with AVX backlash?

#7

Post by yobbo89 »


an image from someones channel, you see the whole gearing system is inline
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maxresdefault.jpg
scopes :gso/bintel f4 12"truss tube, bresser messier ar127s /skywatcher 10'' dob,meade 12'' f10 lx200 sct
cameras : asi 1600mm-c/asi1600mm-c,asi120mc,prostar lp guidecam, nikkon d60, sony a7,asi 290 mm
mounts : eq6 pro/eq8/mesu 200 v2
filters : 2'' astronomik lp/badder lrgb h-a,sII,oIII,h-b,Baader Solar Continuum, chroma 3nm ha,sii,oiii,nii,rgb,lowglow,uv/ir,Thousand Oaks Solar Filter,1.25'' #47 violet,pro planet 742 ir,pro planet 807 ir,pro planet 642 bp ir.
extras : skywatcher f4 aplanatic cc, Baader MPCC MKIII Coma Corrector,Orion Field Flattener,zwo 1.25''adc.starlight maxi 2" 9x filter wheel,tele vue 2x barlow .

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