Which PEC?

[Drac0 (Mark)]

Hi all. I My mount (AZ-EQ5) supports PEC & Permanent PEC (PPEC). Along with that I use PHD2 which has Predictive PEC. I've been wondering which setup could give me the best guiding. I've been trying to get time to test things out but constant clouds/rain has really been restricting time over the last few months so am now seeking advice.

Of course PEC & PPEC are pretty much the same, PEC running off a file loaded by EQMOD & PPEC being stored by the mount. PHD2 Predictive PEC works without any PEC enabled for the mount itself but is also supposed to work with mount based PEC active.

So has anyone any experience using either mount based PEC, PHD2 Predictive PEC or a combination of both.

TIA

Mark

[Cyberman (Rob)]

Mark, I have only used PEC so I can’t comment on the others. With PEC my error has reduced from .8 to about .6. You just have to remember to park the mount after each session so PEC doesn’t get out o sync with the mount. Good luck, Rob

[Drac0 (Mark)]

Thanks Rob - apparently that's the main difference between PEC & PPEC, with PPEC you don't have to remember to park the mount, it stores the position.

Cheers,
Mark

[Startrek (Martin)]

I reduced my guiding error on both of my EQ6-R mounts 18 months ago by doing the following-

Re oriented the camera from 45deg top facing to bottom straight under the OTA pointing down the front tripod leg on my Newts

Rebalance rig slightly east heavy in Ra
Ensure Dec balance is spot on

Fine tuned Ra and Dec worm gears to minimise backlash

Adjusted Ra and Dec drive belts

Use PHD2 PEC algorithm ( I’ve never gone back to using Hysterisis )

On average I would previously guide around 0.75 to 0.85 total

After the above I guide on average around 0.65 to 0.75 and with good nights 0.45 to 0.55 total

PEC training won’t guide you out of trouble on average to poor nights of seeing , Mother Nature is always the winner

Unless your worm drives are pretty bad and you have fairly noticeable PE definitely go for PEC training especially with fully geared mounts ( no belts ) but I’d opt for the above procedures first and see how you guide over many nights in different seeing conditions first.

2 nights ago I was imaging M104 Sombrero Galaxy , guiding was 0.75 to 0.85 early on at low altitudes around 30 to 35 deg , 3 hours later up at 60 deg I was guiding at 0.50 rock solid until the meridian

Guiding error is so dependent on the ever changing atmosphere.

Cheers
Martin

[Drac0 (Mark)]

Thanks Martin - have been working on getting the balancing right & backlash down (currently sub 500ms).

One thing I have decided while imaging tonight is to NOT use PEC/PPEC and PHD2's predictive PEC at the same time. I found that on a number of occasions PHD2 was trying to correct in the wrong direction, RA would start to drift some but instead of issuing pulses for the opposite direction it was doing them in the same direction, making things even worse. The graph was getting well above the 4", even 6" line before it would start to try & pull it back. Needed to stop & restart the guiding to get it back to normal. Not good at all.

Now using PPEC with Hysterisis and currently guiding below 0.7 so I'm happy with that for this mount. Will keep this setup for a few (rare) nights out and see how it goes & maybe test just predictive PEC on it's own at a later date.

Cheers,
Mark

[Drac0 (Mark)]

Given up on all versions of PEC, at least for now. I find that with the mount based PEC my guiding would go to hell when on the opposite side of the pier to where it was trained - probably due to the change from setting up east heavy which becomes west heavy after a flip. And with PPEC in PHD2 I found a similar issue with it issuing guide commands in the wrong direction on occasions making things worse rather than better.

So just back to the basics at least for now.

Cheers,
Mark