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Strange guiding with A-P 1200 GTO and PHD

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#1 PGW Steve

PGW Steve


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Posted 29 April 2009 - 11:43 AM

Last week I was out doing some imaging and the guider was running fine, the graph function had the normal wave look to it in RA and Dec, this was when the scope was on the east side. Later on I did a flip and was imaging on the west side of the mount and noticed that the Dec axis was spiking in a very extreme, but uniform way. It was late and I decided to pack it in, I chalked it up to maybe a weak power pack.

I went out again the other night and was imagaing and guiding without problem on the east side of the mount. I did a flip, and again recalibrated PHD. Same thing when it was guiding, it was cycling north and south by a fair bit. Now it had my attention. I checked for loose bits on the mount and guider, all was well. I purposly changed my perfect balance to load against the Dec worm. Still no change. I then dug around in the keypad for the backlash settings and had '2' for the RA and '3' for Dec. I remember a long time ago setting these per the procedure in the AP manual. I increased the number for the Dec and the graph went really bad....so wrong way....tried level 2, 1, and 0. Now the mount is tracking properly, or so it seemed for the 10 mins I let it run.

It appears that the change I made corrected it, is someone able to help me understand what was going on, and what I did wrong? Attached is a pic of what the graph looked like before I changed the backlash numbers.

*edit* I'm using a SSAG and V1.9 of PHD

Attached Files



    True Blue

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Posted 29 April 2009 - 01:23 PM

The backlash on the AP's should be set at zero. Anything else would mean an adjustment was needed.

#3 nik hodges

nik hodges

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Posted 29 April 2009 - 02:41 PM

agreed, there are a number of threads on the AP yahoo tech group that discuss the same thing and this is what Roland and others recommend

#4 Aquatone


    Ranger 4

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Posted 30 April 2009 - 08:31 PM

Yes I have experienced exactly the same thing with my AP1200. Set the backlash to zero.


#5 PGW Steve

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Posted 30 April 2009 - 10:30 PM

Thanks for the tips, I can't wait to try it out again!!

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