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Measuring periodic error.


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I have a mount review coming up and would like to look at the various options for accurately measuring PE. I have one or two ideas in mind but if anyone has any good suggestions or software recommendations I will be all ears...

Thanks in advance,

Olly

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You don't need fancy software to measure the PE Olly. With a properly polar aligned scope turn off the corrections but run a tracking log. Easiest if the tracking log is reporting the error in arc seconds and not pixels!. You can then plot the graph yourself from the results or transfer to Excel and it will do all the plotting for you.

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I've just measured the PE in my NEQ6 using the log from PHD guiding. I then read it into the free EQMOD PECPrep program which picks out the periodic error signal from the log data. It isolates various harmonics that can be linked to each part of the worm drive and much more. There are some youtube videos to help:YouTube - Broadcast Yourself.

Hope this helps

Mark

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If you have K3CCDTools, the Drift Explorer function will give you a visual plot of RA and Dec wobbles (of a centered guide star) and also reports underlying systematic drift. You can set it to auto-guide and save the corrections log, but I mention it mainly for its usefuleness in producing a real-time plot that lets you watch what's going on.

(Goes without saying that the smoothness and consistency of the PE curve is at least as important as amplitude when it comes to autoguiding.)

Adrian

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Thanks guys. Trouble is, I don't have either Maxim or EQ mod so I really need a freeware that will do it or this review will cost me a bomb! But maybe PHD will do it on its own?

Olly

Unfortunately many folks seem to be under the impression the "EQMOD software" is only for synta mounts when in actual fact it is only the EQMOD ASCOM driver, EQASCOM, that is mount specific. EQMOSAIC, EQTOUR, ASCOMPAD, PECPrep, Perecorder etc. are not specifically tied to a particular mount/equipment types and all are free.

PECPrep is a comprehensive Periodic Error analysis tool and it is able to import data from a whole host of different sources including many freeware guiding apps such as PHD & MetaGuide. There is also a generic template based import mechanism for other text based data formats.

PECPrep

Chris.

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