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CEM-60EC Tracking Oscillations

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#1 HxPI

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Posted 12 September 2019 - 10:13 PM

Has anyone seen this with their tracking? It's a 3Hz oscillation that is visible when zoomed in. Setup included C9.25 EdgeHD, Astrozap dewshield, and ASI183MC. No guiding. No more than 35lbs total weight on the mount. Software used was Sharpcap with zoom set to 200%. Object being tracked was Alberio. Latest mount firmware installed, not beta.

 

I checked the belts but they didn't seem to be loose. The magnetic tension knobs were set not too tight and not too loose. Setup was well balanced and polar aligned. All cabling is through the mount. There was no wind or other disturbances around the setup. I just replaced all the boards in the mount, so I hope that's not the issue. What else could be causing this type of oscillation?

 

Ciao,

Mel

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Edited by HxPI, 12 September 2019 - 11:59 PM.


#2 HxPI

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Posted 12 September 2019 - 10:53 PM

Image of setup:

 

 

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#3 gotak

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Posted 12 September 2019 - 11:24 PM

Oh boy. You got the problem as well. 

 

Yeah that's sort of the SDE that keeps being talked about. It's an oscillation and in some of the FW version it's jerky like what you see.

 

Try 20190716 and see if it makes it less jerky. You'll still have the oscillation just not jerky.

 

BTW why did you change out all the boards?


Edited by gotak, 12 September 2019 - 11:29 PM.


#4 HxPI

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Posted 12 September 2019 - 11:46 PM

Oh boy. You got the problem as well. 

 

Yeah that's sort of the SDE that keeps being talked about. It's an oscillation and in some of the FW version it's jerky like what you see.

 

Try 20190716 and see if it makes it less jerky. You'll still have the oscillation just not jerky.

 

BTW why did you change out all the boards?

Some of the boards were an older version and I was dealing with tracking issues. Decided to upgrade all the boards to the same version and see what happened.

 

Guess I have nothing to lose at this point by installing the beta. I might also try unbalancing the mount in RA and see if that helps steady things as well.

 

Thanks for sharing.



#5 OzAndrewJ

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Posted 13 September 2019 - 12:26 AM

Gday Gotak

 

Yeah that's sort of the SDE that keeps being talked about.

Not so sure there.

True SDE for a 60EC should repeat at a period of 5.54s ( 0.18Hz ) not something like the 3Hz being shown/reported.

For Mel, do you have a short unguided log file of the oscillation

so you can see its direction and amplitude. Ie if it was really bad seeing, both DEC and RA traces should show similar "noise", but if its mainly RA only, and truly 3Hz, then its a new mystery.

 

Edit.. but looking at the orientation of the movement relative to the angle between the stars, it certainly looks like its a predominantly N/S or E/W move.

 

Andrew Johansen Melbourne Australia


Edited by OzAndrewJ, 13 September 2019 - 01:54 AM.

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#6 Der_Pit

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Posted 13 September 2019 - 07:10 AM

I haven't seen Oscillations in SER movies for my mount, but some of my (fast) guiding logs do show a peak at 2.8s.  Though typically with an amplitude below 0.1".

Might at least be a hint that there is something going on in the system at that frequency, that could get excited/amplified under some condition....



#7 RandallK

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Posted 13 September 2019 - 11:31 AM

Just curious....what happens if you try guiding?


Edited by RandallK, 13 September 2019 - 11:32 AM.


#8 HxPI

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Posted 13 September 2019 - 02:20 PM

Gday Gotak

Not so sure there.

True SDE for a 60EC should repeat at a period of 5.54s ( 0.18Hz ) not something like the 3Hz being shown/reported.

For Mel, do you have a short unguided log file of the oscillation

so you can see its direction and amplitude. Ie if it was really bad seeing, both DEC and RA traces should show similar "noise", but if its mainly RA only, and truly 3Hz, then its a new mystery.

 

Edit.. but looking at the orientation of the movement relative to the angle between the stars, it certainly looks like its a predominantly N/S or E/W move.

 

Andrew Johansen Melbourne Australia

 

I don’t have any guiding logs because this is my EAA setup, which I don’t intend to use with guiding. Therefore, I don’t have anything setup for guiding. However, I could try to capture some data with the primary scope, when the next opportunity arises.

 

The oscillations are clearly in one axis, probably RA.


Edited by HxPI, 13 September 2019 - 02:25 PM.


#9 HxPI

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Posted 13 September 2019 - 02:21 PM

Just curious....what happens if you try guiding?

 Not sure what happens with guiding. I intend on using this setup unguided only.


Edited by HxPI, 13 September 2019 - 02:24 PM.


#10 mikefulb

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Posted 13 September 2019 - 03:06 PM

It might be interesting to add weight and so get those counterweights all the way up the shaft and see if the behavior changes.

 

https://astro-physic...ize-guiding.pdf


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#11 HxPI

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Posted 13 September 2019 - 03:19 PM

It might be interesting to add weight and so get those counterweights all the way up the shaft and see if the behavior changes.

 

https://astro-physic...ize-guiding.pdf

That’s an interesting recommendation indeed. Thanks for sharing.


Edited by HxPI, 13 September 2019 - 03:20 PM.



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