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cem120 grinding noises when Dec moves, adjusting mesh?

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#1 markm75c

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Posted 23 February 2020 - 12:28 AM

Are there any other cem120 (non ec version here) users that may have had an issue where when the DEC is moving it often will make a thrashing/grinding sound?

 

Mines nearly there all the time. 

 

Recently too, imaging in nina (asi294mc pro main, 60mm guidescope asi290mm mini and at f7), with good phd2 values or at least good considering my pixel scale, the image shifts up or down over time, despite rms of say 0.30-0.60 (though occasionally it briefly hits 0.80 then back down)

edit: i think my image shift is strictly in the RA axis possibly  (i've verified RA is balanced, but is it possible i dont have enough counterweight despite balanced or some other factor)

Worth noting that my PA was done via sharpcap and it was supposedly good to 9" (excellent in the guide).  If sharpcap cant be relied on and drift alignment in phd2 is the solution, i've not mastered that, perhaps a polar scope (ioptron sells one) can avoid dealing with phd2 drift alignment, if in fact this is a PA issue.  I have everything tied down pretty well, things were fine previously and now they arent as far as i know.

 

I've since redone the wizard and calib in phd2 to be safe.

 

ioptron said that i should adjust the one (or two) meshing screws which i dont quite understand despite looking in the manual.  So i tried a 1/8 counter clockwise turn on the larger one and this made no change to the sound.

 

They claim the sound is "normal", but given my recent moving image issues i'm not sure.

Any thoughts?

 

Thanks in advance


Edited by markm75c, 23 February 2020 - 01:35 AM.


#2 DuncanM

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Posted 23 February 2020 - 01:57 AM

The CEM120 shouldn't make any noises other than a hum from the stepper motors. It does sound like your gear switch mesh needs to be adjusted per page 43 of the manual and/or your mount is unbalanced in Dec. Mounts that use stepper motors are very sensitive to balance issues and it's good practise to carefully balance the mount.

 

The CEM120 should have ~7 arc seconds of periodic error, or less,  in RA, over a 4 minute period, so a slight oscillation in RA whilst tracking is typical even with excellent polar alignment, but it guides out easily. 



#3 markm75c

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Posted 23 February 2020 - 02:11 AM

The CEM120 shouldn't make any noises other than a hum from the stepper motors. It does sound like your gear switch mesh needs to be adjusted per page 43 of the manual and/or your mount is unbalanced in Dec. Mounts that use stepper motors are very sensitive to balance issues and it's good practise to carefully balance the mount.

The CEM120 should have ~7 arc seconds of periodic error, or less, in RA, over a 4 minute period, so a slight oscillation in RA whilst tracking is typical even with excellent polar alignment, but it guides out easily.


Yea that's the part in the manual I tried adjusting. The larger opening. I wasn't sure if both needed turned or just the one

The ra axis is balanced. At least that when horizontal it stays.

How can I look for the 7 arc sec in phd2 over 4 mins. What part of the graph and stats would show that.

#4 DuncanM

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Posted 23 February 2020 - 03:16 AM

Yea that's the part in the manual I tried adjusting. The larger opening. I wasn't sure if both needed turned or just the one

The ra axis is balanced. At least that when horizontal it stays.

How can I look for the 7 arc sec in phd2 over 4 mins. What part of the graph and stats would show that.

 

 

The mount needs to be balanced in Dec as well. 

 

This video may help in understanding gear switch adjustment:

 

https://youtu.be/emjXwHHVlF4

 

PHD2 has an option to track the star whilst turning off guider commands and this can be used to show the mounts raw PE. You can use Pempro log viewer to extract the actual PE from the PHD2 guide logs:

 

http://www.siriusima...tup_1.4.0.0.exe


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#5 markm75c

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Posted 23 February 2020 - 01:14 PM

The mount needs to be balanced in Dec as well. 

 

This video may help in understanding gear switch adjustment:

 

https://youtu.be/emjXwHHVlF4

 

PHD2 has an option to track the star whilst turning off guider commands and this can be used to show the mounts raw PE. You can use Pempro log viewer to extract the actual PE from the PHD2 guide logs:

 

http://www.siriusima...tup_1.4.0.0.exe

Thanks for the tips..

In terms of the movement, this is strange, what i saw in the nina preview didnt match what i thought was going on.  I put the series of files in pixi in blink and there is movement, i guess just dithering, though given the small setting i had, i'm not sure if this is how dithering should appear over time (too much movement maybe or maybe not)

http://youtube.com/watch?v=MPZ3AVbAzV8

 

Ill check out the video for the adjustment, hopefully i can get that adjusted.  As far as balance, both dec and RA are balanced fine.


Edited by markm75c, 23 February 2020 - 01:14 PM.


#6 DuncanM

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Posted 23 February 2020 - 01:40 PM

Thanks for the tips..

In terms of the movement, this is strange, what i saw in the nina preview didnt match what i thought was going on.  I put the series of files in pixi in blink and there is movement, i guess just dithering, though given the small setting i had, i'm not sure if this is how dithering should appear over time (too much movement maybe or maybe not)

http://youtube.com/watch?v=MPZ3AVbAzV8

 

Ill check out the video for the adjustment, hopefully i can get that adjusted.  As far as balance, both dec and RA are balanced fine.

The above is not really useful for determining mount tracking and PE. You really have to use PHD2 (or similar program) to measure the raw periodic error and then analyse it using a suitable software like PEMPro log viewer.

 

You should aim the OTA south and gather your data with the OTA pointed about 45 degrees above the horizon, about two hours from the meridian.



#7 markm75c

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Posted 23 February 2020 - 01:48 PM

The above is not really useful for determining mount tracking and PE. You really have to use PHD2 (or similar program) to measure the raw periodic error and then analyse it using a suitable software like PEMPro log viewer.

 

You should aim the OTA south and gather your data with the OTA pointed about 45 degrees above the horizon, about two hours from the meridian.

I had run that wizard in phd2 last night.. maybe the data points are in the log file.  I meant to take a screen shot.  What i'm saying is that i thought there was massive movement in nina, at least on its preview screen.  In th end i dont think it was correct and if my video loop in blink is just representative of typical dithering then there is no real issue after all (except the grinding noise on the dec).  Ill rerun that wizard if i cant find the results from yesterday



#8 markm75c

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Posted 23 February 2020 - 01:55 PM

I found the Guiding asssistant info in the logs..

INFO: Guiding parameter change, MountGuidingEnabled = true
INFO: GA Result - Backlash= 102  +/-  57 ms (0.8  +/-  0.4 arc-sec)
INFO: GA Result - SNR=37.6, Samples=59, Elapsed Time=147s, RA HPF-RMS=  0.13 px (  0.33 arc-sec ), Dec HPF-RMS=  0.13 px (  0.32 arc-sec ), Total HPF-RMS=  0.18 px (  0.46 arc-sec )
INFO: GA Result - RA Peak=  1.15 px (  2.86 arc-sec ), RA Peak-Peak   3.65 px (  9.10 arc-sec ), RA Drift Rate= -0.91 px/min ( -2.26 arc-sec/min ), Max RA Drift Rate=  0.10 px/sec (  0.25 arc-sec/sec ), Drift-Limiting Exp=   3.2 s
INFO: GA Result - Dec Drift Rate= -0.02 px/min ( -0.05 arc-sec/min ), Dec Peak=  0.69 px (  1.71 arc-sec ), PA Error= 0.2 arc-min
INFO: GA Result - Recommendation: Consider trying to improve focus on the guide camera
INFO: GA Result - Recommendation: Try setting RA min-move to 0.33
INFO: GA Result - Recommendation: Try setting Dec min-move to 0.50
INFO: GA Result - Recommendation: Try starting with a Dec backlash compensation of 100 ms

 

I dont have pempro for viewing the logs, from memory i think that was a pretty expensive package, unless it has a free log analyzer?  It looks like the the RA axis is moving more than the dec in terms of drift, but maybe this is normal?

 

 

Also.. in ioptron panel the sidereal rate is at 0.5x, is this a normal value or should that be 1.0


Edited by markm75c, 23 February 2020 - 01:57 PM.


#9 OldManSky

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Posted 23 February 2020 - 02:37 PM

Use the free PHD2 log viewer that you can download from here:

 

https://openphdguidi...hd2-log-viewer/

 

0.5X is correct for the guide speed.  

 

As far as the adjustment, back off the DEC lock until it's just loose.  Then tighten it down 1/2 turn.  That should do the job.  You don't want them all the way down, or even 1/2 turn off all the way down -- the magnetic locks will take care of keeping things meshed.


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#10 DuncanM

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Posted 23 February 2020 - 03:54 PM

I found the Guiding asssistant info in the logs..

INFO: Guiding parameter change, MountGuidingEnabled = true
INFO: GA Result - Backlash= 102  +/-  57 ms (0.8  +/-  0.4 arc-sec)
INFO: GA Result - SNR=37.6, Samples=59, Elapsed Time=147s, RA HPF-RMS=  0.13 px (  0.33 arc-sec ), Dec HPF-RMS=  0.13 px (  0.32 arc-sec ), Total HPF-RMS=  0.18 px (  0.46 arc-sec )
INFO: GA Result - RA Peak=  1.15 px (  2.86 arc-sec ), RA Peak-Peak   3.65 px (  9.10 arc-sec ), RA Drift Rate= -0.91 px/min ( -2.26 arc-sec/min ), Max RA Drift Rate=  0.10 px/sec (  0.25 arc-sec/sec ), Drift-Limiting Exp=   3.2 s
INFO: GA Result - Dec Drift Rate= -0.02 px/min ( -0.05 arc-sec/min ), Dec Peak=  0.69 px (  1.71 arc-sec ), PA Error= 0.2 arc-min
INFO: GA Result - Recommendation: Consider trying to improve focus on the guide camera
INFO: GA Result - Recommendation: Try setting RA min-move to 0.33
INFO: GA Result - Recommendation: Try setting Dec min-move to 0.50
INFO: GA Result - Recommendation: Try starting with a Dec backlash compensation of 100 ms

 

I dont have pempro for viewing the logs, from memory i think that was a pretty expensive package, unless it has a free log analyzer?  It looks like the the RA axis is moving more than the dec in terms of drift, but maybe this is normal?

 

 

Also.. in ioptron panel the sidereal rate is at 0.5x, is this a normal value or should that be 1.0

I provided a link, above, to Pempro Log Viewer, which is free.

 

The only data which is really useful is the PHD2 guide logs with RA/Dec guiding disabled. You should allow the mount to track for 4-6 worm periods (16-24 minutes).



#11 markm75c

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Posted 23 February 2020 - 04:15 PM

Use the free PHD2 log viewer that you can download from here:

 

https://openphdguidi...hd2-log-viewer/

 

0.5X is correct for the guide speed.  

 

As far as the adjustment, back off the DEC lock until it's just loose.  Then tighten it down 1/2 turn.  That should do the job.  You don't want them all the way down, or even 1/2 turn off all the way down -- the magnetic locks will take care of keeping things meshed.

Thanks, ill give the adjustment a go.

 

The log file works great, one example here, but no drift shown just normal guiding over a long period

Capture.JPG



#12 markm75c

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Posted 23 February 2020 - 04:16 PM

I provided a link, above, to Pempro Log Viewer, which is free.

 

The only data which is really useful is the PHD2 guide logs with RA/Dec guiding disabled. You should allow the mount to track for 4-6 worm periods (16-24 minutes).

That data was during the "Guiding assistant", i thought it had guiding disabled, or maybe not long enough.  Have to wait for another clear shot.  (Sorry i didnt realize that was also a free viewer)


Edited by markm75c, 23 February 2020 - 04:19 PM.


#13 markm75c

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Posted 23 February 2020 - 04:18 PM

I provided a link, above, to Pempro Log Viewer, which is free.

 

The only data which is really useful is the PHD2 guide logs with RA/Dec guiding disabled. You should allow the mount to track for 4-6 worm periods (16-24 minutes).

Actually here it is at least in log view format (over 15mins time with the drift data)

 

CaptureG.JPG



#14 markm75c

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Posted 23 February 2020 - 04:48 PM

Use the free PHD2 log viewer that you can download from here:

 

https://openphdguidi...hd2-log-viewer/

 

0.5X is correct for the guide speed.  

 

As far as the adjustment, back off the DEC lock until it's just loose.  Then tighten it down 1/2 turn.  That should do the job.  You don't want them all the way down, or even 1/2 turn off all the way down -- the magnetic locks will take care of keeping things meshed.

I havent retried the adjustment yet, but confirming..

 

As of now with normal operation both knobs on the dec area are horizontal.. i'm confused by the manual as it states to "release dec axle locking knob", i'm assuming that meant just pull out or did that mean to put in the upright position.  Then move the other knob to the vertical position, then adjust the 5mm screw (after putting the larger knob back to horizontal)?  (do nothing with the 3mm one?)  I cant recall but i think one of the knobs had to move to be able to insert the tool to adjust, i guess if it can go in its in the right position.

 

The 5mm hex screw is for the "gear adjustment" from what i can follow, unsure on the term for the 3mm one?


Edited by markm75c, 23 February 2020 - 04:49 PM.


#15 markm75c

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Posted 02 March 2020 - 12:00 PM

Well i had a chance to try this again.

 

I put the larger tool in the larger opening, after putting the larger lock in the upward position and the smaller in the right (where it was).. but when i try to turn the set screw it doesnt feel like its catching to be able to turn it for some reason.  



#16 DuncanM

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Posted 02 March 2020 - 01:08 PM

Please re-read your manual on page 42 (Appendix E):

 

http://www.ioptron.c...Instruction.pdf

 

The 3mm opening requires a 2mm hex key and the 5mm opening requires a 3mm hex key.


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#17 markm75c

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Posted 02 March 2020 - 01:13 PM

Please re-read your manual on page 42 (Appendix E):

 

http://www.ioptron.c...Instruction.pdf

 

The 3mm opening requires a 2mm hex key and the 5mm opening requires a 3mm hex key.

Thats what i used, for the 5mm opening i put the 3mm hex key in there, but I wasnt able to loosen it strangely, though the first time i tried i was able to.  I havent bothered with the 3mm opening, i assumed only the 5mm is what i should be adjusting.


Edited by markm75c, 02 March 2020 - 01:13 PM.


#18 DuncanM

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Posted 02 March 2020 - 01:22 PM

Thats what i used, for the 5mm opening i put the 3mm hex key in there, but I wasnt able to loosen it strangely, though the first time i tried i was able to.  I havent bothered with the 3mm opening, i assumed only the 5mm is what i should be adjusting.

The manual is pretty clear that in the 3mm opening is a setscrew that needs to be loosened before adjusting the 5mm opening's 3mm setscrew.



#19 markm75c

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Posted 02 March 2020 - 01:30 PM

The manual is pretty clear that in the 3mm opening is a setscrew that needs to be loosened before adjusting the 5mm opening's 3mm setscrew.

I misread that in the manual, i thought the two openings were for adjusting two different things..

 

Yeah it says loosen the 3mm (2mm tool) half turn counter clockwise, then the 5mm (3mm tool) can be loosened).. but does this mean tighten the 3mm one half turn clockwise after adjusting the 5mm opening to "put it back" to where it was though?



#20 DuncanM

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Posted 02 March 2020 - 01:45 PM

The 2mm screw is referred to as a 'set screw' , while the 3mm screw is referred to as the 'gear adjustment screw'

On page 43 it states:

 

 

If the motor stalls or the mount does not tracking smoothly, most likely the meshing is too tight. You may
loosen it by about 1/8 turn (or less for tracking). Tighten the set screw to LOCK the gear screw
(important), then test the mount.
Adjust again if needed, but no more than ΒΌ turn in total.
If you feel there is free play between the worm and gear, you may tighten the gear screw to eliminate it.

 


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#21 Michaeljhogan

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Posted 02 March 2020 - 03:40 PM

This is why i had mine for a year when given the chance to sell it i threw it at him for 2500 euro and never looked back also same thing with CGX-L

two weeks old they tried the old "Hello give it to us and we will fix it no problem" to run out the clock so after 30 days you cant get your money back.

 

I learned the hardway the first time with the CEM-120 and in a moment of madness i made bought the CGX-L after two weeks got my refund so

after getting my money back 3200 Euro for CGX-L and pier plate and selling CEM-120 2500 thats 5700 then had 3500 in the bank and some rammed

me from behind wrecked my old care got nearly 2000 euro and here i am with 11.200 Euro on the brink of getting the ultimate GM2000 HPS II

 

Only three months ago it didnt even come into my mine to buy a new mount i had being burned by Chinese mounts twice by end on may ill

have 13.150 euro full price on the GM2000 HPS II i bought into the ioptron hype from this website and it cost me dearly then people telling me all the

CGX and CGX-L problems with belts and motors and been fixed Ioptron are no different to Celestron


Edited by Michaeljhogan, 02 March 2020 - 03:42 PM.


#22 markm75c

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Posted 02 March 2020 - 09:45 PM

Ok, so this time i was able to losen the smaller set screw, made sure the left lock was upward.. tried to loosen the 5mm(3mm tool) but cant seem to latch on to anything.  Maybe the cover needs to come off to figure out whats going on (though the cover screws arent standard).  So i tightened back the smaller set screw, turned it on aiming straight up again, then moved the dec axis, no noise.  I guess at this point ill leave it be till i hear it again (its also warmer today, seemed to all start in colder weather).



#23 rgsalinger

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Posted 02 March 2020 - 10:02 PM

Some people know how to fix things and some people don't. Those who don't, like me send back things that don't work. Others apparently like to rant and rave instead.

 

Some people haven't a clue about how to diagnose guiding problems and just start opening up their mounts because they can do so. The same one or two people just keep posting over and over again in the hopes of dissuading people from buying perfectly good mounts. Any mount from any vendor can be bad. If it's bad send it back or have it fixed under warranty. The iOptron warranty is two years last time I checked. 

 

You do not need to move the cover. There's a nice PDF on the iOptron website showing how to do it. 

 

 

 

Rgrds-Ross

Attached Files


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#24 markm75c

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Posted 02 March 2020 - 10:07 PM

Some people know how to fix things and some people don't. Those who don't, like me send back things that don't work. Others apparently like to rant and rave instead.

 

Some people haven't a clue about how to diagnose guiding problems and just start opening up their mounts because they can do so. The same one or two people just keep posting over and over again in the hopes of dissuading people from buying perfectly good mounts. Any mount from any vendor can be bad. If it's bad send it back or have it fixed under warranty. The iOptron warranty is two years last time I checked. 

 

You do not need to move the cover. There's a nice PDF on the iOptron website showing how to do it. 

 

 

 

Rgrds-Ross

Mine is back to normal, but yes i followed that guide, something is a miss with the larger diameter set screw, or i just goofed something.  But either way its now normal with no sounds so I dare not touch it unless it returns :) 


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#25 astrohamp

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Posted 05 March 2020 - 08:17 PM

Good to read yours "is back".  Adjustments can sometimes be problematic which is why the squeak in mine, I believe due to cold weather operation, has gone untouched this winter.  Not enough run time to know what is up and if it is a problem or just an iOptron mount 'noise'. 




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