EQ6-R Phd2 guiding and backlash issue

[Icesheet]

I haven't guided for some time now but I was recently out guiding for the first time with my new EQ6-R.  The first night I used an Orion mini guider with Altair GPCAM2 and the guiding I was averaging  was 1.7"RMS. I spent most of the night trying to work out why as I had routinely guided sub 1"RMS with this on my old HEQ5. In the end up I only managed 40mins imaging time. However, the stars looked good albeit probably bloated.

I had read about the PPEC function on the EQ6-R so the next night I decided to run AutoPEC on EQMOD to generate a PEC curve and load that to the mount so I could use the PPEC function and hopefully improve my guiding. I also used my main imaging set up of Esprit 100ED and ZWO ASI1600mm to give me the highest resolution I could achieve at 1.43"/px. I have loaded the PHD2 graph and log below. As you can see the first hour or so was used to record AutoPEC on EQMOD. This averaged 1.22"RMS error. When I switched to PPEC this dropped down to 1.02"RMS which although better still left me disappointed given that my HEQ5 gave better results and that was just a push the button and go job.

I then ran the guiding assistant which I have never used before. Screenshots attached from that below. The main take home from it is that my mount seems to have excessive DEC backlash of  over 7sec!

I have to admit that I am no expert with this so I'm hoping someone with experience can look into this and advise. Is this backlash the main source of my poor guiding or is there anything else going on here? Can this be solved by optimising guiding parameters and perhaps balancing my set up better to counter it or is this backlash severe enough that it requires some mechanical attention? I'm really reluctant to get the tools out for such a new mount.

As always any help or advice appreciated!

 

Edit to add:

•Not entirely sure what seeing was but at least average probably better  

• I believe there was a focus issue with the GPCAM the first night so that probably contributed to the poorer guiding the first night  

PHD2_GuideLog_2019-11-11_011955.txt

Edited November 12, 2019 by Icesheet

[Icesheet]

I have received some good feedback from the Phd2 group on this. It seems I haven’t set up things properly and that may be exaggerating the backlash issues. Just need to wait for another clear night to see!

[Ryan_86]

Hi oal, just read you post. 

May I ask,  didi you resolve it? 

My Eq6r pro just reported 3.7 sexonds of dec backlash. I tinkered with my deca and ra worm adjustment because I could wobble axis. However there's lots there, so not sure whether to adjust mechanically again or isnit a guiding setting 🤔

Here's a pic of graoh, 10 ga. 

Total rms 0.6 with strong winds 😳 No images though, as half of my shutter wouldn't open lol. 

Thanks

Ryan

[Icesheet]

Hi,

I did get sub arc sec guiding in the end but I’m afraid I can’t remember what I did now. Also, I no longer have that mount. I recommend going onto the PHD2 group. The people there were very helpful and responsive.

https://groups.google.com/g/open-phd-guiding

If you’re guiding at 0.6” RMS I wouldn’t worry too much! Just get the shutter sorted and you’re good to go 👍

[Clarkey]

9 hours ago, Ryan_86 said:

However there's lots there, so not sure whether to adjust mechanically again or isnit a guiding setting

I would suggest that 3.7 seconds backlash is excessive for the guiding to deal with. You shouldn't be able to feel any play in either axis. There are plenty of guides on line regarding the worm gear tuning. Basically, keep tightening until it binds, then back it off slightly. With my HEQ5 and AZ-EQ6 I can get the backlash below 1 second. I don't know how old your mount is, or whether it has been serviced, but I would strongly recommend giving it an overhaul if you can. I have stripped down and rebuilt both of mine and they perform much better now.

[Ryan_86]

Thanks foe your replies guys. 

 

Yes Clarkey, I've adjusted the dec and ra worm gear meshing because i could feel some play in both axes. After lot's of adjustments I'm pretty certain there's no backlash or binding. Also the belts move precisely when moved at 0.2x via the hand controller. Also I've adjusted plastic casing where the counter weight shaft goes through and the ra nut behind the polaracope. Balancing is spot on and really smooth.

My guiding was consistently at 0.6rms that night even with really strong winds. I'm wondering whether the winds effected it along with my balance on the 3rd axis not being good enough as it does pull to the left when parked and clutches are released. 

I was unable to take any subs due to my shutter being stuck closed. I'll try these and go again. 

Does this calibration graph look ok, Indone thia bwfore running thw guide assistant. 

Sorry guys I've been out of the game for 3 years so am a bit rusty 😬😂👍🏼

Thanks again guys 

Ryan

[michael8554]

Hi Ryan

I would expect PHD2 to have put up a warning about the Cal ?

Along the lines of "RA and Dec rates differ" and "Cal too high in Dec"

Cal at  +/- 20 degrees of Dec = 0 if possible.

But if PHD2 accepted the Cal, then you're good to go with a GA run.

Michael

[Ryan_86]

Hi Micheal, 

No there were no warnings following calibration bwfore running a GA. 

Next time I'll calibrate as close to 0 dec as possible, I can get within 20deg for sure. 

I didn't manually clear the backlash prior to running PHD2, I'll try that also. 

Maybe I'm going a bit OTT with this but was a bit taken back by the backlash as I've adjusted the meshing and cant feel any play or binding.

Much appreciated 👍🏼