Re: PEC Does Not Improve Periodic Error - What should I expect in improvement?

Nov 5, 2015



#56410 Nov 5, 2015

I was wondering what kind of improvement I am supposed to get with the PEC function turned on.�� I am currently at the following level of measured Periodic Error as measured utilizing PemPro.

Peak to Peak PE:3.56 Arc-SecsCurve Fit��- RMS Error: 0.109 Arc-SecsMax Error:0.28 Arc Secs

I utilized PemPro to program the Gemini unit yet, I actually don't get any improvement.�� My limited measurements this go around and the last time I tried this, actually show a small degradation of performance to say 3.75 Peak to Peak.�� Am I just at the limits of performance and PEC just does not work that well or have I done something wrong?�� What is the expected PEC improvements at the level of PEC that I have.


#56411 Nov 5, 2015

3.5 peak to peak doesn't sound bad at all before PEC! ��How many worm cycles of data did you collect before programming?��

RMS value indicates that fit error is very low (0.109 arcsec) that's an indication that PEC should be able to correct most of the error, as it's truly periodic with the worm cycle.

The fact that you don't see much of a change after programming PEC indicates that perhaps PEC was not programmed, or that PEC was not turned on after programming. Another possibility is that you didn't run the calibration wizard prior to doing the analysis/programming.

My experience with Pempro is that it either doubles my periodic error (in which case I need to invert the curve before programming) or reduces it significantly.��


�� �� -Paul


#56412 Nov 5, 2015

You need to turn PEC on in the Gemini controller after each power up unless you are using ASCOM to drive in which case you can this automatically.... IMHO it should default to ON if you have saved a PEC profile, but sadly it doesn.t. ��Dave From: [] Sent: 05 November 2015 18:42To: Losmandy_users@yahoogroups.comSubject: [Losmandy_users] PEC Does Not Improve Periodic Error - What should I expect in improvement?


#56435 Nov 12, 2015

Thanks again Paul,

I had to go out of town and was not able to look at this reply.�� I ran about seven or so cycles for the PEC.�� I also took apart the mount cleaned everything and put it back together before I tested.�� I had not tried to polar align again prior to testing.�� I have now polar aligned again and for the first time every, utilizing pempro I have no error in azimuth.�� I am going to for the altitude correction tonight weather permitting.Then I am going to test everything again.�� The error should be about the same.�� I am going to focus on seeing what I can do with the PEC turned on.

Thanks for the input.�� It does seem like the PEC is not turning on.�� I will also check it tonight.

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