23 replies to this topic

[Tom62e]

Has anyone ever come across this? . . . When my mount is parked facing Polaris and I start looping 3-sec images, the stars bounce back and forth on my screen.

 

A 3-sec exposure shouldn't be long enough to produce anything more than some oval stars.  Certainly not what I'm seeing (stars are bouncing 2 to 3 inches on my screen).

 

Maybe it's always done this and I never noticed because I never loop images?

 

I went outside and checked the axes were locked (which they were).  I then checked the DEC for excessive backlash (there was virtually none).  Then I grabbed the top of the scope and gently shook it back and forth in RA.  It moved a little bit back and forth (perhaps 1/2 inch in each direction, maybe a little less).  I'm not sure if this is normal.  In any case it wasn't moving (to my eye) when I was looping images and yet I was still seeing the stars bounce back and forth.

 

Here is a Dropbox link to the video of me shaking the RA back and forth.  Is this normal?

 

https://www.dropbox....t=ikhko2pd&dl=0

 

 

Any thoughts?  

Edited by Tom62e, 10 February 2025 - 05:34 PM.

[bignerdguy]

Has anyone ever come across this? . . . When my mount is parked facing Polaris and I start looping 3-sec images, the stars bounce back and forth on my screen.

 

A 3-sec exposure shouldn't be long enough to produce anything more than some oval stars.  Certainly not what I'm seeing (stars are bouncing 2 to 3 inches on my screen).

 

Maybe it's always done this and I never noticed because I never loop images?

 

I went outside and checked the axes were locked (which they were).  I then checked the DEC for excessive backlash (there was virtually none).  Then I grabbed the top of the scope and gently shook it back and forth in RA.  It moved a little bit back and forth (perhaps 2 inches in each direction..  I'm not sure if this is normal.  In any case it was moving when I was looping images and yet I was still seeing the stars bounce back and forth.

 

Any thoughts?  

2" of movement??? That's a bit excessive.  It shouldn't move any more than 5 mm to 8mm at most when locked down firmly but not overtight.  If its moving 2" then something is loose. It sounds like either the backlash is worse then you thought or the mount lock wasn't holding the axis firmly.  You shouldn't need to crank the lock arm down hard but lightly firm should hold the axis properly and allow for little to no movement.  If it still moves that much then i would service the mount and see if there is anything internal that might be causing it.  you can try adjusting the backlash first but i would suspect bearings or internal washers have probably worn instead.

[Tom62e]

2" of movement??? That's a bit excessive.  It shouldn't move any more than 5 mm to 8mm at most when locked down firmly but not overtight.  If its moving 2" then something is loose. It sounds like either the backlash is worse then you thought or the mount lock wasn't holding the axis firmly.  You shouldn't need to crank the lock arm down hard but lightly firm should hold the axis properly and allow for little to no movement.  If it still moves that much then i would service the mount and see if there is anything internal that might be causing it.  you can try adjusting the backlash first but i would suspect bearings or internal washers have probably worn instead.

Can the RA axis have backlash?  I thought only Dec suffered backlash.

 

Also, the clutches are actually more like the axes locks you see on an iOptron mount.  They're either all the way on or all the way off.  My mount is the SW CQ350 btw.

 

Now that I'm thinking about it, it's nowhere near two inches.  Let me edit that quick.  probably more like 1/2".

Edited by Tom62e, 10 February 2025 - 03:59 PM.

[Tom62e]

Here is a Dropbox link to the video of me shaking the RA back and forth.  Is this normal?

 

https://www.dropbox....t=v52et1jm&dl=0

[bignerdguy]

Can the RA axis have backlash?  I thought only Dec suffered backlash.

 

Sure you can. You can have backlash on both axis.  This is common on all EQ mounts.

[Tom62e]

Sure you can. You can have backlash on both axis.  This is common on all EQ mounts.

Huh, no kidding.  I never knew that. 

 

This mount is only 9 or 10 months old, I wonder if they would tune it up under warranty.  I think I'll make a call to Starizona where I bought it and see what they say.

 

Thanks Bignerdguy!

[Jared]

Backlash is normal in both RA and Dec. It’s just that you don’t tend to notice it in RA since the motors never have to "reverse". It just slows down (perhaps to zero) or speeds up when guiding, but never reverses, so you don’t experience backlash. It’s still there, though.

 

Not sure what mount you have, but worm gear drives usually have a bit of backlash. If you are seeing enough to make the stars move a couple inches across the screen, though, that sounds like too much.

[Tom62e]

Backlash is normal in both RA and Dec. It’s just that you don’t tend to notice it in RA since the motors never have to "reverse". It just slows down (perhaps to zero) or speeds up when guiding, but never reverses, so you don’t experience backlash. It’s still there, though.

 

Not sure what mount you have, but worm gear drives usually have a bit of backlash. If you are seeing enough to make the stars move a couple inches across the screen, though, that sounds like too much.

This makes perfect sense.  I have the Sky-Watcher CQ350 EQ mount.

 

Hopefully I can have it adjusted under warranty!

 

Thank you!

[kathyastro]

Hopefully I can have it adjusted under warranty!

By all means inquire about a warranty adjustment.  But don't get your hopes up.  Backlash adjustment is typically considered a DIY adjustment.  I don't know that specific mount, but there are videos for most consumer mounts showing how to adjust the gears, if you want to start researching the DIY option.

[Tom62e]

By all means inquire about a warranty adjustment.  But don't get your hopes up.  Backlash adjustment is typically considered a DIY adjustment.  I don't know that specific mount, but there are videos for most consumer mounts showing how to adjust the gears, if you want to start researching the DIY option.

I'm concerned if I open the mount, it might void my warranty.

[bignerdguy]

Found this which may help you adjust the backlash on the mount.  FYI the vendor will usually not adjust any backlash under warranty unless something is broken to cause that.

 

https://cdn.astrobin...24ef6b676e0.pdf

[Tom62e]

Found this which may help you adjust the backlash on the mount.  FYI the vendor will usually not adjust any backlash under warranty unless something is broken to cause that.

 

https://cdn.astrobin...24ef6b676e0.pdf

Thanks!!

[rj144]

It happens when your mount is parked?  

[Tom62e]

It happens when your mount is parked?  

Yes, parked using NINA.  EQMOD also verifies the scope is parked.

[SubaruB4]

Sure you can. You can have backlash on both axis.  This is common on all EQ mounts.

Yep.. thanks to here I was told to check mine since I have having issues with PA.. boy the blacklash in the dec was really bad.. even the RA had a decent amount on my mount (Sky watcher GTI) it's not that hard to adjust much better but waiting for the skys to clear to try again.

[Tom62e]

Yep.. thanks to here I was told to check mine since I have having issues with PA.. boy the blacklash in the dec was really bad.. even the RA had a decent amount on my mount (Sky watcher GTI) it's not that hard to adjust much better but waiting for the skys to clear to try again.

Same here.  I have heavy clouds for the next several days.

[bignerdguy]

Yep.. thanks to here I was told to check mine since I have having issues with PA.. boy the blacklash in the dec was really bad.. even the RA had a decent amount on my mount (Sky watcher GTI) it's not that hard to adjust much better but waiting for the skys to clear to try again.

You're welcome.  FYI make sure after you adjust the backlash you put your equipment on the scope and test slewing to see if it binds.  I did that after i took it outside and found really quick that it didn't bind when i had no equipment on it but boy did it bind with all of it on!  I had to go inside to get my allen wrenches and screwdriver and perform an emergency field adjustment.  Try doing it in the dark with a dinky red flashlight to illuminate everything... Not fun.

[SubaruB4]

You're welcome.  FYI make sure after you adjust the backlash you put your equipment on the scope and test slewing to see if it binds.  I did that after i took it outside and found really quick that it didn't bind when i had no equipment on it but boy did it bind with all of it on!  I had to go inside to get my allen wrenches and screwdriver and perform an emergency field adjustment.  Try doing it in the dark with a dinky red flashlight to illuminate everything... Not fun.

Whoa! thanks for the heads up! I have it setup in the house now just going to check it out sadly it looks like asiair has no type of simulation of tracking without having to do a polar alignment. So I'd just have to slew around then.

[bignerdguy]

Whoa! thanks for the heads up! I have it setup in the house now just going to check it out sadly it looks like asiair has no type of simulation of tracking without having to do a polar alignment. So I'd just have to slew around then.

yeah thats all you need to do.  use the hand controller and do a fast slew and see what happens.  Do it both directions in both RA and DEC and make them long movements.

[SubaruB4]

yeah thats all you need to do.  use the hand controller and do a fast slew and see what happens.  Do it both directions in both RA and DEC and make them long movements.

Well I had binding but not because of the adjustments but the dovetail bar hit the tripod and the lens hood hit the mount but that was extreme for the lens hood because it was pointed to the ground and I found that turning tracking on while slewing will cause it to keep on going without pressing the arrow keys. I might need to adjust the camera on the dovetail bar as the angle of where the corner hit could be a real possibility of it happening

[Tom62e]

I have a few hours of clear sky tonight before the clouds roll back in for the rest of the week.  Going to see if the bouncing happens again.  The only issue is that it's kind of windy, which may skew the test.

 

I'm also using a much wider field (shorter FL) scope.  My new ASKAR SQA55 arrived, and I want to test it sooner than later.  So, any movements should look much smaller on the screen compared to the 800FL I was using when this all started.

 

I'll post back here in a few hours.  Everybody cross your telescopes!   

[SubaruB4]

What's the limit on wind? I never got my setup running that night and we had like 14 mph wind gusts it didn't feel very strong (I was near the beach) but I wonder if it would of effected the setup anyways?

[Tom62e]

Well, it's pretty windy right now and my CQ350 with the AskarSQA55 isn't budging at all when parked.  So maybe my last experience was a fluke.  Maybe I missed something.  But I don't think so and here is why . . .

 

After being parked for a while, I slewed the scope to a high-in-the-sky target and started guiding for a bit. Everything was perfect for the first few minutes. Guiding was excellent between .40 and .55. Then all of the sudden the RA went on a trip to who-the-hell-knows-where. It just went on an excursion. No matter how high I turned up the Aggression, no response.

 

Now I'm seeing another issue. The mount appears to not be tracking (y'all are getting this report LIVE by the way). PHD2 keeps losing the guide star because the mount cannot track properly.  I returned to home, initiated guiding assistant again (thereby slewing the scope to celestial equator), and Viola' the mount is tracking again fine.  And the guiding is ~0.43 RMS.

 

I'm starting to think perhaps the scope was too well balanced and it displayed the RA backlash. This would explain the RA excursions. The sudden failure to track, I'll chalk up to a one-off for now. If it happens again (the failure to track), I'll be worried and will need to investigate further.

 

Tomorrow, I'll call Starizona and see if the warranty allows me to open the mount for RA backlash adjustment. If not, they are an authorized SW dealer and repair shop. I'll just pay them to make the adjustment.

 

FYI - it's a 2.5-hour drive . . . ughhh!  Always worth it though.  Starizona is awesome.          

Edited by Tom62e, 11 February 2025 - 09:59 PM.

[SubaruB4]

Well, it's pretty windy right now and my CQ350 with the AskarSQA55 isn't budging at all when parked.  So maybe my last experience was a fluke.  Maybe I missed something.  But I don't think so and here is why . . .

 

After being parked for a while, I slewed the scope to a high-in-the-sky target and started guiding for a bit. Everything was perfect for the first few minutes. Guiding was excellent between .40 and .55. Then all of the sudden the RA went on a trip to who-the-hell-knows-where. It just went on an excursion. No matter how high I turned up the Aggression, no response.

 

Now I'm seeing another issue. The mount appears to not be tracking (y'all are getting this report LIVE by the way). PHD2 keeps losing the guide star because the mount cannot track properly.  I returned to home, initiated guiding assistant again (thereby slewing the scope to celestial equator), and Viola' the mount is tracking again fine.  And the guiding is ~0.43 RMS.

 

I'm starting to think perhaps the scope was too well balanced and it displayed the RA backlash. This would explain the RA excursions. The sudden failure to track, I'll chalk up to a one-off for now. If it happens again (the failure to track), I'll be worried and will need to investigate further.

 

Tomorrow, I'll call Starizona and see if the warranty allows me to open the mount for RA backlash adjustment. If not, they are an authorized SW dealer and repair shop. I'll just pay them to make the adjustment.

 

FYI - it's a 2.5-hour drive . . . ughhh!  Always worth it though.  Starizona is awesome.          

Hmm wow I hope that wont happen to me.. I have yet to track yet.. I think the first time I did get the PA good enough I must of forgot to tighten the RA down and it ended up pointing at the ground..