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AZ-EQ5 Mechanical Weirdness

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#1 MattZ40

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Posted 21 June 2021 - 08:34 AM

I have an AZ-EQ5 that I've used maybe a dozen times, always in EQ mode. While its tracking is an improvement over my previous ALT-AZ mount I haven't been able to get exposures longer than about 90 seconds without oval stars. My scope has a 1250mm focal length and I know that exacerbates the problem. I recently started using PHD guiding and the tracking graph looked pretty awful and I could feel a bit of backlash in the RA axis, so I thought I'd go through the backlash adjustments / gear cleaning procedures that are shown in some posts and on youtube.

One thing I found is that with the motor removed so that I can spin the worm gear easily by hand there is a very noticeable 'rumble' as the counterweight shaft moves toward pointing straight down, from either side of the pier. Moving it up is smooth, but moving down is not. Pushing down on the shaft as it moves doesn't stop the rumble. It does it both before and after cleaning the gears and adjusting the backlash, and whether I spin the worm gear fast or slow. After reassembling the mount I can't tell if it's doing it while tracking since the movement is so slow and increments so small, but I suspect that it is.

 

Has anyone seen this before, or have any advice on how to cure it?



#2 lattitrail

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Posted 21 June 2021 - 09:35 AM

My thoughts are that the "rumble" would be caused by a moving part binding up as it moves. Identifying what part is binding or moving roughly is the first step. Once identified, you can figure out what it takes to correct it.

 

I hypertuned an older celestron mount with a kit I purchased from Deep Sky Products a few years back. Celestrons were famous for not having enough clearance around the brass ring gear's shaft and housing which would cause a similar bind as it spun and result with quite awful tracking. The solution was to tediously sand it down by hand and polish the shaft until it would spin freely without binding. I don't know if this is your problem or not, if it is I think the EQ5 has a belt mod kit that might be an easier solution. Another possibility is there could be a bearing on the worm gear or RA axis that is bad or maybe even too tight. Really you won't know what's causing the rumble until you spend some effort moving various parts around by hand until you can identify the cause of the rumble.

 

If all else fails, Deep Space Products has hypertune kits for and will service the EQ5. I would suggest checking them out, they can sell you a kit and instructional dvd or you can send your mount to them and they'll do it for you. 

 

Best of luck!     



#3 MattZ40

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Posted 21 June 2021 - 10:45 AM

My thoughts are that the "rumble" would be caused by a moving part binding up as it moves. Identifying what part is binding or moving roughly is the first step. Once identified, you can figure out what it takes to correct it.

 

I hypertuned an older celestron mount with a kit I purchased from Deep Sky Products a few years back. Celestrons were famous for not having enough clearance around the brass ring gear's shaft and housing which would cause a similar bind as it spun and result with quite awful tracking. The solution was to tediously sand it down by hand and polish the shaft until it would spin freely without binding. I don't know if this is your problem or not, if it is I think the EQ5 has a belt mod kit that might be an easier solution. Another possibility is there could be a bearing on the worm gear or RA axis that is bad or maybe even too tight. Really you won't know what's causing the rumble until you spend some effort moving various parts around by hand until you can identify the cause of the rumble.

 

If all else fails, Deep Space Products has hypertune kits for and will service the EQ5. I would suggest checking them out, they can sell you a kit and instructional dvd or you can send your mount to them and they'll do it for you. 

 

Best of luck!     

Thanks for the advice lattitrail. I checked the Deep Space Products website and they don't show any kits for this particular mount. The AZ-EQ5 is belt drive, so it's different than the EQ5. With the worm gear removed the RA axis will swing like a pendulum if the counterweight shaft is pushed less than an inch in either direction and released, and I don't feel any binds while spinning it 360 degrees.

With the worm gear in place I can manually turn it to spin the axis 360 degrees and don't feel any binds there either. It's baffling.

I'm waiting for some higher quality grease and ceramic worm gear bearings to arrive. In the meantime I'll do some outdoor testing if the clouds go away.




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