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Old 18-09-2019, 10:08 AM
Startrek (Martin)
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PHD2 PPEC on Low end mounts

Other than improving the mechanical efficiency of my HEQ5 mount with Rowen Belt mods, replacement of bearings etc... is there any advantage using the PPEC algorithm in PHD2 over hysteresis to improve guiding. Iíve read a few posts on CN where people have only improved their error by 0.1 or 0.2 arc sec using PPEC whereas other didnít see any improvement at all. I guess each mount is different and each night is different but being a predictive algorithm it should improve guiding slightly one would think. My guiding has been ok considering I have a newt on board with 67% payload capacity but I would like to get it a bit tighter. I use the guiding assistant sometimes but most times I can read my mount fairly well and tweak the settings according to conditions and performance
I like to get some feedback from members who use PHD2 PPEC on low end mounts

Thanks in advance
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Old 18-09-2019, 05:00 PM
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peter_4059 (Peter)
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I'm using it and I think it works well. There is no downside.

Last edited by peter_4059; 21-09-2019 at 12:33 PM.
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Old 18-09-2019, 07:56 PM
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ChrisV (Chris)
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I tried it for a while and then went back to hysteresis. And I don't remember why. I can't see that anyone has done a comparison of the different algorithms. Be nice to see ...
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Old 18-09-2019, 08:29 PM
Startrek (Martin)
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Thanks Peter and Chris
Next time Iím out Iíll try it on my HEQ5
From memory the worm cycle period on my HEQ5 is around 638sec so Iíll use that in the Period Length
If I find no improvement after a few nights out using PHD2 , I might try PEC training through EQASCOM and EQMOD
For my other mount , the EQ6-R , does anyone know the worm cycle period ( sec ) ? as I might try PHD2 PPEC on it too.
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Old 18-09-2019, 08:56 PM
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billdan (Bill)
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The older EQ6-Pro worm cycle is approx' 478.7 secs. Not sure if the R version has a different gear in it though.
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Old 19-09-2019, 07:21 AM
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doppler (Rick)
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Another thing that can cause issues is drive motor speed, I have a suspicion that mine runs a smidge fast, this was noticeable when I was only tracking, not guiding.
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Old 19-09-2019, 10:18 AM
Jasp05 (Aaron)
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What kind or RMS Error are you getting on an average night with your Heq5?

I've got mine down to around 0.6-0.8 on a good night and no more than 1.2 on bad seeing. I've also got the belt mod and replaced the bearings etc.

But I haven't applied PPEC to my mount as yet. Been meaning to try it out also.


I'm not convinced that PPEC will get the guiding that much lower than it currently is with the HEQ5 internals.
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Old 19-09-2019, 11:31 AM
Startrek (Martin)
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Rick,
I run my mount tracking unguided on Sidereal for a minute or 2 and can still get decent star shape
After 30 minutes itís only drifted off the bullseye at 2 x zoom on BYEOS a small amount
So I think sidereal tracking is sort of ok , but polar alignment plays a big part too

Aaron
My guiding error on most nights with the HEQ5 is 1.20 to 1.40 arc sec
Iím finding that dithering is knocking the DEC around a lot and recovery / settle is taking up to a minute even on a low Dither
Iíve never got it down to 1 arc sec or below
Most posts Iíve read where members have done the Rowan belt mod and / or bearings etc are guiding below 1 arc sec error
Your balance and payload is a big factor as well, Iím carrying a 6Ē f6 newt , DSLR, guide scope , finder scope , dew heater bands etc.....so roughly about 9kg , so my payload is up there ( it should really be no more than 7.5kg on these mounts )
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Old 19-09-2019, 02:40 PM
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doppler (Rick)
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My rms is usually around 0.4 arc secís on the dec and 0.8 on the ra and averages at 0.7 total. It rarely goes over 1. I think you need a pretty regular wave in the ra drive for pec to work. My ra errors are mostly a bit random so pec training hasnít done much good on my setup. Having the mount on a pier makes good polar alignment easy, as well as increasing payload capacity.
Rick
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Old 19-09-2019, 07:51 PM
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RobF (Rob)
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+1 what Rick said

You'll get most benefit if you PEC curve for RA isn't too wild. Remember there can be signficant inter-mount variability for chinese mounts.

My HEQ5Pro seems to have reasonable and predictable peak to peak PE and I feel PPEC helps, especially if you image a few nights in a row.

My belt modded EQ6 has some steeping PE moves in its RA worm, so still benefits, but little harder to predict exactly when the worm is approaching that steeper period.


For large gear mounts like EQ8 you would think there would definitely be benefit, as Peter has said.
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  #11  
Old 19-09-2019, 08:08 PM
Startrek (Martin)
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Thanks Rob
Next clear night in Sydney Iíll try it on my HEQ5 and when Iím down at my dark site next Iíll try it on the EQ6-R mount too

In regard to doing a future belt mod to my HEQ5, do most people buy direct from Rowan Engineering in the UK or through a vendor in Australia ?
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Old 19-09-2019, 08:40 PM
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RobF (Rob)
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I got mine from Rowan astro UK without issues some years ago.
Be curious if others have bought from Aus ok.

Should have also mentioned, arcsec tracking is ultimately all relative around your imaging scale of course. I'm often tracking around 1.2" RME but very happy on nights it settles around 0.6-0.9" on the HEQ5Pro.

I'm normally imaging at 2.1 arcsec/px though.....
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Old 19-09-2019, 09:01 PM
Startrek (Martin)
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My image scale is oversampled on both rigs
The 6Ē f6 newt with HEQ5 is 0.98 arc sec / pixel
The 8Ē f5 newt with EQ6-R is 0.88 arc sec / pixel
Iím imaging with a canon 600D with pixel size of 4.3um

One thing I forgot to mention, when Iím away down the coast at my dark site using the 8Ē f5 newt and EQ6-R mount Iím usually guiding on good nights between 0.75 and 1.20 arc sec error which is a huge improvement on the HEQ5 in Sydney where I canít get below 1.20 arc sec error
The belt driven DEC on the EQ6-R must make all the difference plus better bearings and worm drive etc...on the bigger more expensive mount
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Old 19-09-2019, 09:24 PM
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RobF (Rob)
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Yes, people seem to generally comment that the average Skywatcher mount performance has continued to improve in recent years, particularly the later belt driven mounts.
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  #15  
Old 19-09-2019, 10:15 PM
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doppler (Rick)
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I also got mine direct from the UK, took a bit over a week.
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