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Yikes spikes!


Mike Hawtin

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Anyone come across this sort of thing before?  It's an autoguiding trace of an AZ-EQ6, the following thirty minutes had three more RA spikes at wide but random intervals but the curious thing is all of the excursions including the sole Dec one had very similar profiles, the same duration and amplitude though in different directions.  The mount was running on a large capacity deep cycle battery and using PHD2 with ST4 guiding, I tried two cables to eliminate that factor.  I could return the mount but it is a replacement for a duff IEQ45 PRO and I don't want to put the dealer to unneccessary expense shipping mounts back and forth to Cyprus so I would rather do all I can here to get to the bottom of the problem.

TIA

Mike H

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While it could be an inherent fault in the mount I'd expect that problem to be external to it. Those are truly enormous spikes. I don't use PHD but it will presumably have a parameter to limit the maximumum movement it will impart in any single guide input. Is this value set nice and low? If it isn't it could be the guide input itself that is launching the spike.

You're quite certain that there is no possibility of cable snag? Or other physical impediment?

I'd also be thinking about power supply but I know little about batteries. Can they produce surges? Expert needed!

And if this is an original type Lodestar the ST4 connection is awful. However, when it fails you normally see a slow drift off target, not and out and back spike.

Olly

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A daft question first off Mike - There was no dithering enabled?

After that I have no idea, but thought I'd check that first!

Sara, no dithering here, me perhaps but not the guiding!

Olly, I don't think it's cable snags, RA and Dec would spike together and the RA excursions go in both + and - directions.  The guide camera isn't a Lodestar and the guide set up used runs my Atlux with no problems.  I suspect it's an electronics issue but as you say it needs an experts input.

Mike

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Mike & myself have discussed this via PM and I believe the mount has a similar mechanical fault to the original AZEQ6 I was supplied, my RA axis would also perform huge spikes while guiding seemingly at random. I didn't spend anytime investigating the cause as my dealer was FLO who immediately whisked it away to be replaced by a spanking new one that worked perfectly.

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How did you arrive at those RA settings ? 50 and 0 look a bit strange

Dave

Dave I set aggression to 50 to stop overcorrection and  Hysteresis to zero to avoid clouding the mounts performance with another variable, in normal use and in the absence the spikes I would fiddle and tinker with the setting a lot to get optimum performance.

Mike

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Michael, I have only captured single excursions so far and the sub seemed ok but there are times when I get multiple excursions during a ten minute period which is my normal sub length for broad band.  The trace in my first post has three excursions in a six minute period and is reasonably typical, I would expect these to be visible but will have to wait for clear skies before I can check, however the forecast is not good for the next week here.

Mike

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Thank you all very much for your suggestions folks, problem solved, a chap over on Cloudy Nights suggested I update the firmware for the m/c control board and sure enough it has worked a treat, two hours guiding so far without a single blip, Bliss.

Mike

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Isn't the astro internet wonderful!  :smiley:

Yes Peter it certainly is.  I would probably have thrown the towel in long since without the help and support of people happy to share their hard won experience via the internet, it renews your faith in the essential kindness of people.

Mike

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