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What's wrong with my guiding?

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Replied by nMAC on topic What's wrong with my guiding?

I now that It was already mentioned here some time ago but it seems the HEQ5 is not supported as the options do not appear on INDI control panel.
The same happens with the Vixen GPD2 I have now, it has a Skywatcher goto kit and I am using it with eqmod, but the options do not appear also.
Last edit: 4 years 11 months ago by nMAC.
4 years 11 months ago #38191

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Replied by nMAC on topic What's wrong with my guiding?


Again I am glad I could really help. It's kind of hard getting the values right. It's trial and error, sometimes, even for the same equipment.. and those 450+ ohhh boy....
I tried that....and it made me nervous :-D
4 years 11 months ago #38192

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INDI EQMod does not support PEC unfortunately, although it is supported in ASCOM EQMod.

Gonzo, you mentioned you were not too happy with something after you rebuilt the mount. I also have an HEQ5 Pro, and I just found I had to make an adjustment to the worm meshing on my RA. It had a little play in it that I could feel by hand, and it made a little knocking noise. The mount has been tuned before. But I move it around a lot.

If your RA worm drive is not meshing optimally, it very well may be the reason your RA guide scatter plot is so elongated. The settings you've worked on may have helped but ultimately, if my presumption is correct, it will have to be mechanically addressed.

www.astro-baby.com/heq5-rebuild/heq5-we1.htm
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4 years 11 months ago #38193

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"elongated" yes, I was watching the RA RMS and it was going up and down from 1" to 1.4" in cycle over and over.
As in an oval shape on the RA while the DE was a circle.

At least now the guiding now is sorted out, very surprise that I had to lower the exposure time on the QHY5, as I mentioned earlier I really thought you needed more exposure. Well that's what I read on many blogs and forums.
4 years 11 months ago #38208

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I have noticed a varying RMS in RA as well depending on the direction in the sky that I am guiding in. In my case this implies a not 100% perfect balance and I know that e.g. the polar scope is slightly offset w.r.t. the center of the hour axis. When balancing the scope in various positions it may not be immediately obvious that there is an imbalance but this may become visible when guiding. Perhaps as a test you could try guiding for, say, 15 minutes with the telescope pointed at different AltAz (i.e. north east at 60 degrees elevation, south east at 60 degrees etc) and see if there is a difference. That way you may be able to determine if imbalance may be a contributing factor.
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4 years 11 months ago #38210

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I've mostly used PHD2 with my belt modded and otherwise slightly tuned (and overloaded, which is why I recently upgraded to EQ8) HEQ5 as its PPEC guiding mode seems to work very well with this mount and routinely got under 1" RMS, usually around 0.8" and at best around 0.5", partially depending on the direction of the target (high DE targets guide better) and noticed that slight imbalance (east heavy) on RA does help quite a lot. I have a fixed remote location so I couldn't shift the weight when meridian flipping, but also the site is such that I would image mostly towards west of meridian so I balanced the rig accordingly. I use the target pier side option to image slightly before the meridian which extends the target area.

I did get the internal guider to work quite well too, but running PHD2 isn't really that much work and did give noticeable improvement as my imaging pixel scale is quite small so I switched to that. Also PHD guiding assistant and guide logs helped a lot in getting the settings tuned with less guess work. I use 0.5x guide speed and 2 or 3s exposures with OAG and Lodestar X2. With faster guide speeds the guiding became quite restless and with slower ones it didn't react quite fast enough to periodic errors so 0.5x was a suitable compromise.
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4 years 11 months ago #38290

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"PPEC guiding mode", I guess that's from using PHD2 right? As eqmod does not have PEC for this mount(HEQ5pro), as far as I know.
www.indilib.org/devices/telescopes/eqmod.html
"PEC/PEC training is enabled in INDI EQMod for mounts which supports it, EQ8, AZEQ5/6, EQ6R too apparently."

From the Synscan manual:
Last edit: 4 years 11 months ago by Gonzothegreat.
4 years 11 months ago #38298

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Yes, it's one of the RA guiding modes in PHD2, Predictive Periodic Error Correction, where PHD2 "learns" the periodic error frequencies during guiding and gradually starts to correct them already in advance. This starts to help after one worm period, before that it behaves as normal hysteresis mode.
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4 years 11 months ago #38299

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Are there ballpark numbers for how much PPEC improves guiding? For instance, I have two setups: an 80 mm F/5 refractor on an HEQ5 and a 203 mm F/5.4 RC on an EQ6-R. The first has a pixel size of about 1.7", the second om 0.7". If I can reach 1.0" guiding RMS on the HEQ5 then I wouldn't need the PPEC, right? On the second I usually have around 0.7" and better guiding RMS so perhaps there it could improve the RMS?


Wouter
4 years 11 months ago #38300

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For ballpark numbers my purely anecdotal experience is that on a typical night before the PPEC starts to work I usually get around 1" RMS and it gradually drops to around 0.8". This is with a similar setup as you have (8" TS RC with reducer, though my pixel scale is 1.02"/pix) but HEQ5 instead of EQ6-R. The most noticeable visible improvement in my case was that shape of stars is better thanks to less oscillation in RA direction due to PE. My DE error is small to begin with as I have fixed setup with good PA.
4 years 11 months ago #38302

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Having a read through that PHD2 best practice pdf openphdguiding.org/PHD2_BestPractices.pdf
They are talking about long exposure, 2s to 4s, when I tried that my mount didn't like it at all...
4 years 11 months ago #38307
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I typically use 2.0 sec exposures on both my setups and get the numbers I stated in an earlier comment. It truly seems that one's mileage may vary...
4 years 11 months ago #38314

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