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Tracking woes


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9 hours ago, newbie alert said:

Sorry I don't follow, I haven't got a heq5 but I don't understand what you're trying to mesh and then you say Ra is always meshed?

 

RA backlash doesn't affect tracking / guiding, whilst imaging RA is only ever driven in one direction it never reverses so is always meshed.

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9 hours ago, Pitch Black Skies said:

He's just saying to loosen the mesh between the worm gear and the RA gear ⬇️

Screenshot_2022-05-01-23-42-14-432.jpg.9c5fcf5c78c5a0f9ecb8b9a3e30d2f6d.jpg

and then mesh them back together gradually with the grub screws.

When he said RA is always meshed he was referring to getting the best results rather than having a fraction of play between the mesh.

 

Why remove the belt to adjust the worm.. to adjust the worm correctly it's best to have the mount loaded as you would whilst using it and run the gears and listen to the harmonics... If you don't then you can only go by feel which won't tell you much once you've snugged the worm carrier bolts down if anything changed.. if you run the gears you can hear it..

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Posted (edited)
14 hours ago, newbie alert said:

to adjust the worm correctly it's best to have the mount loaded as you would whilst using it and run the gears and listen to the harmonics..

With the belt removed, the RA is still loaded.

As I've mentioned in an earlier post there, listening to the harmonics proved misleading. Despite having no binding noise, when I turned the gear by hand it was still far too tight and sticking.

See the previously attached video clip.

Edited by Pitch Black Skies
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Posted (edited)
On 02/05/2022 at 00:19, newbie alert said:

Ra is always meshed

The RA worm is always in contact with the crown wheel because it is constantly driven at or close to sidereal rate. Backlash is not important.

That is in contrast to the DEC motor, which if well polar aligned, should remain stationary. Any guide pulses could send DEC in in either direction. Backlash is critical.

HTH

 

 

 

Edited by alacant
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Posted (edited)
14 hours ago, Starflyer said:

whilst imaging RA is only ever driven in one direction it never reverses so is always meshed.

Thanks, that makes sense. I think I misunderstood Alacants statement also. I was thinking if the balance was off, then any backlash might be noticeable as the RA would be bobbing over and back when sending pulses.

Edited by Pitch Black Skies
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Just now, Pitch Black Skies said:

With the belt removed, the mount is still loaded.

As I've mentioned in an earlier post there, listening to the harmonics proved misleading. Despite having no binding noise, when I turned the gear is was still far too stiff and sticking. See the attached video clip.

Try slewing the mount without the belts attached... If there's other reasons causing the axis to bind it won't be solved by adjusting the worm, you have to solve those first and then adjust the worm

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8 minutes ago, newbie alert said:

Why remove the belt to adjust the worm

The OP is diagnosing inconsistent RA worm rotation. If he does not disconnect the belt, then he has not isolated the RA worm; he is also rotating against the belt tension, intermediate pulley and of course the motor.

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1 minute ago, newbie alert said:

won't be solved by adjusting the worm, you have to solve those first and then adjust the worm

Please see my previos posts. The OP has not yet replaced the RA worm shaft bearings, We are assuming that these are OK. If the test I outlined is successful (I believe it was) then this obviates the need to have to dismantle further. IOW, keep it as simple as possible;)

Cheers

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1 minute ago, alacant said:

The OP is diagnosing inconsistent RA worm rotation. If he does not disconnect the belt, then he has not isolated the RA worm; he is also rotating against the belt tension, intermediate pulley and of course the motor.

I don't think he is... The spike in the guide graph isn't coming from the worm as it's not consistent with a worm period.. it's coming from elsewhere

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Posted (edited)
3 minutes ago, newbie alert said:

The spike in the guide graph isn't coming from the worm

We've moved forward from there. The OP has since discovered an inconsistent rotation in RA. Let's fix that first and try again;)

HTH

Edited by alacant
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1 minute ago, alacant said:

Please see my previos posts. The OP has not yet replaced the RA worm shaft bearings, We are assuming that these are OK. If the test I outlined is successful (I believe it was) then this obviates the need to have to dismantle further. IOW, keep it as simple as possible;)

Cheers

That could be a likely cause, either the bearings are locked up, ie too tight and the bearings are crushed causing jitter, or they have seized.. 

I did mention this on the first page... 

The worm mesh should be the last thing to do

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4 minutes ago, newbie alert said:

the bearings are locked up

The OP has already proved that this is not the case.

Thanks. Must go. Not a fiesta here today:(

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13 hours ago, michael8554 said:

The RA problem might be as simple as "Chasing the Seeing"

Oh right. I'm feeling positive that it was the super tight mesh I found in the RA worm gear and crown. It can move much more freely now that I've loosened it. As soon as I have a clear night I can test it and record the results.

Would you recommend longer exposures in general Michael? Would the seeing not affect the DEC axis as well?

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Posted (edited)
On 02/05/2022 at 09:00, Starflyer said:

whilst imaging RA is only ever driven in one direction it never reverses so is always meshed.

If I have pulses on either side of the RA graph does that not mean one side is accelerating tracking and the opposite side is reversing it?

My understanding is that if there is backlash, the pulse is reversing the tracking rate into the backlash.

Edited by Pitch Black Skies
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Posted (edited)
10 hours ago, Pitch Black Skies said:

one side is accelerating tracking and the opposite side is reversing it

Hi

No. The 'pulse' on the opposite side simply reduces tracking rate temporarily for the length of time specified so that the sky can 'catch up'. The worm and crown are in constant mesh.

Cheers

Edited by alacant
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Posted (edited)

Good news and bad news.

The good news is that I think the guiding graph is more steady since loosening the tight worm mesh.

The bad news is that the spike in the RA graph remains and is now more distinct.

Interesting, the spike is consistent at approximately 2 minute intervals.

See the spike every couple of minutes ⬇️

Screenshot_2022-05-04-22-59-29-295.thumb.jpg.2e0464c0cd1e481100078eb9308472d8.jpg

 

See the spike up close ⬇️

Screenshot_2022-05-04-23-01-49-441.thumb.jpg.94ceded63ebfb50c90788b58fcb92c3b.jpg

 

The spike is consistent with a full rotation of the stepper motor (122 seconds) or the gear attached to it's shaft ⬇️

IMG_20220505_015523.thumb.jpg.6dd2eba8c1e6741e1911f9b6030f529e.jpg

I think the next action will be to swap the motors around? 😟

Edited by Pitch Black Skies
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Just wondering what I should do about this. The mount is only a few months old. Is a problem like this to be expected from a mount at this price range? To be fair, I don't think it's impacting my images but it just doesn't sit right with me. I was expecting it to be more accurate. Am I being a bit too fussy?

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2 minutes ago, Pitch Black Skies said:

Just wondering what I should do about this. The mount is only a few months old. Is a problem like this to be expected from a mount at this price range? To be fair, I don't think it's impacting my images but it just doesn't sit right with me. I was expecting it to be more accurate. Am I being a bit too fussy?

Here is simple thing that you can do.

Swap RA and DEC gear. They should be the same, but just in case there is some case of defect on RA one - you should see the difference with replacement.

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3 hours ago, Pitch Black Skies said:

Would this be periodic error then?

That is really strange. If you changed the gear itself - maybe it is the motor (shaft) that is the problem?

Can you perhaps swap those (I'm not sure if they are the same, but they did look the same from what I remember when I was doing mod to mine HEQ5)?

Otherwise, I can't really tell what could possibly be ~2minute long as far as periodic error goes.

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14 minutes ago, vlaiv said:

Can you perhaps swap those

I swapped the both the gear and motor. Could it have anything to do with powering the mount from an ASIAair?

Could having the belt adjusted too tight cause problems? I have it fairly tight and it looks to be more responsive when turning it by hand.

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8 minutes ago, Pitch Black Skies said:

I swapped the both the gear and motor. Could it have anything to do with powering the mount from an ASIAair?

Could having the belt adjusted too tight cause problems? I have it fairly tight and it looks to be more responsive when turning it by hand.

I had issues with too loose belt (it was fairly tight - but it still needed more tightening), but that created 13.6s issue - as teeth meshing was improper.

Not sure what could be issue with belt that shows only on full revolution by stepper shaft. If there was something wrong with belt then it would either show on each tooth or on whole "belt revolution" - which is more than one complete worm period - and that is 10+ minutes.

Maybe there is something wrong with idler? Can you inspect it to see if it has a bump on it or if it is at an angle or whatever?

Don't know what the period of idler is - probably related to its diameter (diameter of part that holds belt - from image it looks like the same as motor gear +/-). Idler can sometimes "slip" - it is not in sync and won't produce exact period - but it will be close to what can be calculate from its diameter.

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54 minutes ago, Pitch Black Skies said:

anything to do with powering the mount

A separate power supply is always a good idea. 

Otherwise, are you sure are there are no external sources of interference? Air conditioning, refrigerator, water thermostat, bird scarer...

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Posted (edited)
3 hours ago, vlaiv said:

Maybe there is something wrong with idler?

I've started the installation again from the start. It seems I have followed all of the instructions correctly. I can't see any defects in any of the parts.

I've decided to let about 4mm lateral play in the idler by adjusting the collar. I had it set so as that there was no lateral play. Maybe this will make a difference.

IMG_20220508_182906.thumb.jpg.7d10fe94705e95136ae3fb4301a58ec2.jpg

Edited by Pitch Black Skies
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