Mount Periodic Error

Hi Bill!
PE is an issue you can handle.
First of all there are software solutions to correct this (periodic error control) and furthermore to record the errors and permanent correct them.
If you do guiding the PE is just one more error within the whole system, which is corrected by the guider.

I combined both with my EQ6R (EQMOD) and Phd2 and I am happy with it.

To face PE by hardware would mean you need perfect parts installed in the mount which is really expensive.

Cheers
Mike

Bill,

I own a Mach 1. I  think its native PE was ~ +/- 3" Peak to Peak. I used PEMPRo to reduce it to around +/- 1" Peak to Peak. Recently, I changed the chip on my CP3 which would  cause the mount to lose its  PE curve. What I find is that there is no difference in the guiding performance when I didn't use PE correction.

I too upgraded the chip in my AP1200 and have to redo the PE. Also using PemPro for this. Very nice and simple program that walks you through the process and also has a very good polar alignment program in it for fine tuning down to sub arc sec. My PE peak to peak was 2.8 ARC-SEC before I started but clouds moved in before I could finish. I'll let you know how it turns out.
Scott

With my EQ6R-pro and WO GT81iv+OAG, my first experience with recording a PEC curve left me with a random spike at the overlap point where the cycle began to repeat. I noticed it in the guiding every time it came around again so I removed the PEC training and figured I would retry it another night, but clear nights have been rare here lately so I haven't been able to try again without wasting imaging time.

After cleaning/re-greasing the tapered roller bearings, reducing the bearing pre-load to be less than stock, and adjusting the backlash, my typical guiding is already about 0.5-0.65"rms depending on seeing/altitude of the target. My absolute worst guiding can be in the 0.8-0.9" range, and my best so far (for only about 30mins) was ~0.35"rms, so I'm already well into the range where I'm pleased with the mount without PPEC enabled.

I'm usually shooting with the GT81 at 385mm so obsessing over achieving <0.5"rms feels kind of pointless, and though I do have a 6SE which could probably benefit from better guiding, I wasn't going to bother changing anything until I came across a program called "PECprep"(that I'm assuming is equivalent to PEMpro). It lets you import PHD2 logs, aligns different individual periods of guiding time, identifies specific mechanical harmonics, performs signal analysis and conditioning, and lets you export a conditioned curve to be used for PPEC training.

I imported my last imaging night's PHD2 logs and according to the "auto filter" analysis, my peak PE was +1.09" to -1.08". If the correction works as expected, it's estimating my residual PE to be +/-0.45" for PHD2 to deal with. It was extremely easy to set up(assuming it works and I didn't overlook something haha), so I figure it's worth a try. All that's needed is to choose your mount from the list or enter its parameters manually, *import your PHD2 log file, hit auto-filter, save the EQMOD output file, and train the mount. I've got it trained for my next night of imaging to see if I notice any changes in my guiding(hopefully positive ones). If not, I can just disable PPEC and try again another night.

*forgot a step