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Can inbalance or cable tension cause tracking error?


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#1 pesa

pesa

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Posted 13 November 2015 - 01:20 AM

Hi

 

As I wrote above, is that possible ?

Specifically for me, I have hard to understand tracking error - usually in dec - and I have no servo error reported in autoslew.

 

Shouldnt ANY pointing error caused by inbalance or Cable drag result in servo error reported?

Put it this way: could misbalace or Cable tension cause pointing error WITHOUT autoslew reporting servo error?

 

Setup is extremely ridig, Concrete filled pier that is on solid rock. Tube is N10 so that should be very stiff as well. Secondary is firmly locked.

Pole error is 1.0'/0.3' rec/dec. Small camera/filter Wheel on ok3Z.

 

same tracking error with/without MLPT.

 

 

pelle



#2 MarkS

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Posted 13 November 2015 - 04:22 AM

It is possible to get oval stars without a servo error being reported.

 

Balance needs to be good when you do Autofind and Homefind. Then check to see that your cables aren't dragging. I have a DDM60 standard, and have used Camera and fan cables as light as possible consistent with low electrical resistance, and I arrange them to hang freely at all positions. They must all be in place when balancing.

 

Then if balance is good you should have no problems.

 

Mark



#3 LucMurphy

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Posted 20 November 2015 - 08:53 PM

Yes it is possible.

I had to replace the stock FLI Camera power cable because it is fairly rigid in warm temperature but it is getting solid in sub-zero temperature. Even with good cable management, it was dragging the mount.

To make sure, you need to do a "time flex" measurement (in Sequence). The default parameter is measuring time flex when the tube points toward the zenith. To perform a better diagnosis, you may have to measure 2 or 3 more positions. The different positions will induce different tension in the cable (or should at least) and therefore should produce a different time flex measurement.

 

 

Regards

Luc



#4 pesa

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Posted 25 November 2015 - 04:37 PM

Thanks for your responses both.

 

What setting do you use under ServoSetup/Sensitivity? The lowest you get when dragging the potentiometer is 0.05, does that work for anyone? Feels like a mosquito landing on the tube would cause servo error then!

 

pelle



#5 MarkS

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Posted 26 November 2015 - 10:43 PM

If you set it to the lowest setting the mount may refuse to move at all! I haven't looked at this for a while, but I set it at 1degree and never altered it. On one occasion I had inadvertently shifted the slider to zero - the axis froze, causing great panic!

 

Mark






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