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Help needed with the Dec guiding in PHD.

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#1 Rexcat

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Posted 13 September 2019 - 11:14 PM

Hi All,

 

I've have been successfully getting constant results guiding my iOptron iEQ45 with PhD for a while now until I had to replace the Dec circuit board in the mount a few weeks ago. Now the Dec guiding has a funny pattern where the dec moves off 4 to 6 arc seconds in one direction then goes off in the other. See the graph below. I'm using the default settings in PhD as I have always. Does anyone know why this is happening?

 

PHD-Graph.jpg

 

Any help would be greatly appreciated. 

 

Paul 

 

    



#2 rgsalinger

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Posted 13 September 2019 - 11:44 PM

For starters you have the aggression for DEC set to 100 percent. Set it down to 70 and see what happens. What you really need to do is to post a complete log which starts with a calibration and goes for 15 minutes at least so that it can be analyzed by the PHD mavens who haunt this forum. Dec guiding is also sensitive to polar alignment but this does not look like a PA problem.  Finally, most guiding problems that "crop up" are due to a bad calibration - nothing more - so that log comes in really handy.

Rgrds-Ross


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#3 happylimpet

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Posted 14 September 2019 - 12:15 AM

This looks like a mechanical/physical issue, not anything to do with software etc.


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#4 Rexcat

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Posted 14 September 2019 - 02:12 AM

I had to wait for a pier flip, then started PhD over, here is the log and screen shot. 

 

Attached File  PHD2_GuideLog_2019-09-14_011151.txt   39.88KB   3 downloads

 

PHD-Graph-2.jpg

 

 

I saw that with the scope pointed into the western sky there wasn't the problem, so after checking the R.A. balance I went back into the eastern sky and found the problem has returned. Here is the log and screen shot from guiding in the east again:

 

Attached File  PHD2_GuideLog_2019-09-14_011151.txt   62.14KB   5 downloads

 

PHD-Graph-3.jpg

 

I'm puzzled...

 

Paul



#5 rgsalinger

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Posted 14 September 2019 - 08:31 AM

Yes I agree with happylimpet. This looks like a mechanical problem. However, what mechanical problem only effects the DEC axis? Looks like it's backlash. You get backlash in DEC from poor balance. If it was poor polar alignment you would not get backlash you'd just get large corrections typically. What I would do first is to check the DEC balance over the entire 180 degrees. At the same time make sure that the mount is not binding when everything is fully connected. If you don't find the problem then try guiding with the main scope/camera just to make sure that the guiding system itself isn't the problem - bad mounting, loose connection, etc. If the main camera shows the same effect then you know that your guiding solution is good and you can concentrate on the rest of the system. 

 

Rgrds-Ross


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#6 Rexcat

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Posted 14 September 2019 - 10:25 AM

All right, thanks for the ideas everyone!

 

I'll check things out and see what I can find.

 

 

Paul




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