54 replies to this topic

[OzAndrewJ]

Gday Damo

I think I'm turning into a PEC addict

Nahhh, its just another diagnostic tool in the arsenal ( as is FFT analysis ).

If you can pro actively remove the bulk of the errors before guiding, it makes a the guiding a lot easier.

I always suggest people do a long duration plot with PEC off then on to get a baseline, then enjoy yourself.

At a later date, ,if something looks odd, just redo the plot and compare to earlier datums to get a hint of what might have changed.

 

I've run the new curve through PEMpro and If I understand this correctly I think I'm now getting 4.3 arcsecs pk-pk with the PEC on.

Yes and no, as it changes between each tooth, which is normal for the gearing Meade uses.

I replotted your data without it being overlayed by period as it gives a different view.

( you can see a scale at the top that shows the worm periods as a guide )

I see you still have a small high freq ripple in your data and that wont guide out at the frame rate you are using.

If you use the full range of the FFT window in the viewer, you will see this actually shows at 90x the worm period

and based on your gearing, this indicates the gear on the motor is eccentric.

Its only about 1arcsec pk-pk, but swapping motors might give a better result, but its a pain to do :-)

Just a game of chasing diminishing returns

 

Andrew Johansen Melbourne Australia

 

 

 

 

[Damo19]

Thanks Andrew,

 

The Pempro log viewer looks to be a very useful / powerful tool, especially when you know what you are doing

 

Below is a snapshot of the PHD guide graph while the PEC is active. I was imaging M81 (bode galaxy) at the time so Its a bit of a cheat as this galaxy is close to the celestial pole, but even so achieving a total RMS 0.4 arc-secs was not possible before without the help of the PEC. Not too shabby at all for an LX85  

 

 

 

[Menocchio]

Cheers again! After updating PEC for a few nights now, it has easily made at least an arcsecond of difference, and along with incorporating the multi-star guiding in PHD2's dev build, I'm rarely seeing my graph go beyond the 1" mark. I had no idea the LX-85 was even capable of this kind of precision. That one patchette of code has been a game changer lol. 

Edited by Menocchio, 27 April 2021 - 03:25 AM.

[OzAndrewJ]

Gday Menocchio

Good to hear.

If you have a reasonably good gearbox, then the PEC will be repeatable and if smooth as well

a PEC model can really help.

When its a moonlit night, whats always fun is to turn PEC off

and start a PHD log with guiding turned off ( via the brain )

Let it run for 2 -4 revs of the worm, then turn PEC ON and do another 2-4 revs.

Load it into the PEMPro viewer and overlap by period to see how consistent it is.

Andrew Johansen Melbourne Australia

[Andynator]

Anyone willing to do this mod for $$ if I mail them my Audiostar handset?