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No permanent PEC

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#1 Kenny2004

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Posted 25 June 2009 - 07:46 AM

On my HEQ5/Sirius mount there is no permanent PEC. Always puzzling to me why most mounts don't seem to have this feature. I guess I need to buy a higher end mount? ;)

#2 UniversalMaster

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Posted 26 June 2009 - 02:02 AM

On my LXD75 I have to remember to "park" the mount, otherwise it will not remember the PEC index and you have to retrain the mount. I'm also puzzled why they make this, it makes the feature completely useless IMO.

#3 neptun2

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Posted 26 June 2009 - 02:33 AM

It is not useless if you have permanent setup. At least in synscan the pec training is made with reticle eyepiece under high power (>300x) and the hand controller just records the corrections that you make to keep the star in the center of fov and plays them back during the tracking. I suppose that when you make the training this way you are trying to correct not only the periodic error but the erros in balancing, polar alignment and any occasional events like seeing and wind. When you are not working with permanent setup next time you observe the balance and polar alignment will be at least slightly different as wel as the occasional events so if you play back the old corrections the result will not be good. If you make the pec training with software and camera the results should be much better. I don't know if you use for example eqmod with it's tools for pec training if you can load the pec later again (so it is kinf of permanent pec) but i think that it should be possible. so maybe this is the reason.

#4 Anand Rajiva

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Posted 26 June 2009 - 04:17 AM

Hi all,

It is not useless if you have permanent setup.

I fully agree to this. A PEC training is time consuming and if it has to be done again and again it is, IMHO, useless.

I do not know why most controllers do not have such feature, but the Gemini System and the controller I use have a permanent PEC. With my setup I even do not have to park the mount as the controller supports Autoparking.

I suppose that when you make the training this way you are trying to correct not only the periodic error but the erros in balancing, polar alignment and any occasional events like seeing and wind.

This is true and that’s why PEC Touch Up was born. PEC TouchUP is a system that allow you to improve the last PEC training without doing a complete new and time consuming training. Maybe EQMod do support something like PEC TouchUP as well.

When you are not working with permanent setup next time you observe the balance and polar alignment will be at least slightly different as wel as the occasional events so if you play back the old corrections the result will not be good.

If the saved training is good or not depends mostly on how much time you invested with the training and the alignment of the mount. Also it depends on how the training is done. Most controllers supports the training of only one period that limit the accuracy a lot. If you can train the PE over several worm periods the end result is much better because errors that not apply to the PE will mostly not occur in the same position of the worm.

If you make the pec training with software and camera the results should be much better.

I think this is not true as the pulses of a software, driven by a camera, are in most cases to fast. There are not to many PEC Table entrys to hold that much corrections of such system. Also the camera brings a lot other problems, like seeing, into the system. I suggest to always do a maunal training, specialy then when you can’t do a PEC TouchUP or the training is limited to one worm period.

The best results, it almost eliminate the PE completely and no training is needed at all, is to use a encoder driven PEC. The Meade TDM (a external box that uses the ST-4 connector for corrections) or EPEC (a similar feature but without a external box) uses this techique. A encoder measures the PE in realtime, or with the Meade system the encoder position is compared with the elapsed time, and the controller eliminates the PE. For such a system just a encoder in the RA axis and some electronic that supports that encoder is needed. The encoder driven PEC (EPEC) do not only eliminate the worm PE, it also eliminates all other errors appearing in the reduction gear boxes etc.

CS

#5 rmollise

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Posted 26 June 2009 - 08:51 AM

On my HEQ5/Sirius mount there is no permanent PEC. Always puzzling to me why most mounts don't seem to have this feature. I guess I need to buy a higher end mount? ;)


I'm not too convinced PEC is much necessary with these mounts. Their errors are generally smooth and regular, and autoguiding is usually enough. If you do want PPEC, just get goin' with EQMOD. It's better than the HC in many other ways as well, and will also enable you to use Pempro.

#6 Chris Curran

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Posted 26 June 2009 - 09:32 AM

Pempro

yum, yum... good stuff.

#7 Anand Rajiva

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Posted 26 June 2009 - 01:04 PM

I'm not too convinced PEC is much necessary with these mounts. Their errors are generally smooth and regular, and autoguiding is usually enough. If you do want PPEC, just get goin' with EQMOD. It's better than the HC in many other ways as well, and will also enable you to use Pempro.

yes, but all this solutions require a PC and a lot extra equipment like a extra power supply. If you have to move to get to a dark sky this is a lot stuff to handle. But you are right, if autoguiding with a PC comes into play there is no need to even think about PEC.






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