Poor guiding with CEM120 after firmware upgrade

[Jeff Squires]

Hello.  I have been experiencing terrible guiding two nights in a row with my CEM120 since upgrading to the newest firmware and Commander 7.0. Does anyone have a clue what can be causing this? I see a definite pattern in RA that was never there before. I checked balance, recalibrated, polar alignment, etc. Equipment is C14, focal reducer, OAG, ASI2600MM.  If someone can help point me in the right direction in would really be appreciated.

[Jeff Squires]

Here is a better picture of my guiding graph.

[Jason Schella]

Hey Jeff,

You'll need to upload your guide log in order for the people on the forum to help you. You can't tell anything from just a picture. 

Best of luck, 

Jason

On Sun., Nov. 7, 2021, 6:54 p.m. Jeff Squires, <squire...@gmail.com> wrote:

Here is a better picture of my guiding graph.

--
You received this message because you are subscribed to the Google Groups "Open PHD Guiding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to open-phd-guidi...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/open-phd-guiding/01af0895-387b-4a2a-b465-161f2b7aa280n%40googlegroups.com.

[Bryan]

Jeff

Best way to upload the logs is https://openphdguiding.org/getting-help/

Bryan

[lmcl...@umich.edu]

Hi Jeff,

I'm seeing the same thing with my CEM120 -- guiding has deteriorated from what it was with the older firmware.

Nothing has changed at all except upgrading the firmware and Commander 7.0.

Lamar

[lmcl...@umich.edu]

Hi Jeff,

I went back to the previous firmware and Commander 6.331 and I'm back to getting really good guiding with PHD2.

HC V2  : 200110

Main   : 191120

RA     : 190820

Dec    : 190820

Catalog: 150429

I'm going to wait until I see that iOptron has made some type of corrections to the firmware before I'll try upgrading again.

Lamar

[Noah Lambert]

As someone who has a CEM120 on the way to solve a guiding issue with my EQ6R-Pro, how do you like the guiding? How can I also avoid some of these issues? 

[lmcl...@umich.edu]

Hi Noah,

I think this new update from iOptron was mostly to correct problems with the EC and EC2 models.  But just as Jeff has mentioned, the guiding was much worse with this new firmware/ASCOM version for our CEM120s.

I'm using an OAG with an ASI174mm Mini guide camera and imaging with an ASI2600MC Pro at about 2413mm focal length with a Meade 12" LX850 ACF on the CEM120.  For PHD2, I usually set the exposure time to 3 secs, sometimes going to 4 secs if the seeing is not steady.

Make sure to set both guide rates to 0.90.  For Dec, I use Resist Switch with Aggressiveness 60 and MinMo 0.40, of course changing the MinMo based on the seeing.  For RA, I use Predictive PEC with Predictive Weight 85, Reactive Weight 70, and MinMo 0.20; again adjusting based on seeing.  I start the Period Length at the 239.45 and have Auto-adjust period checked.  You'll have to experiment with this some because sometimes it might be better to not have that checked.

I usually get an average of 0.40 total RMS, sometimes down to 0.30 but always below 0.50.

Lamar

[Jeff Squires]

Hi Lamar.  I'm glad to hear that I am not the only one experiencing this!  I would love to try reverting back to the old firmware but I only see the most recent release on the iOptron website.  How did you do it?

Thank you for taking the time to respond.

Jeff

[Jeff Squires]

Nevermind I found the archived firmware link on iOptron.com.  I will attempt to revert back to an older version and will report back with my findings.

Jeff

[lmcl...@umich.edu]

Hi Jeff,

iOptron has the archived firmware for the CEM120 at this link:

https://www.ioptron.com/Articles.asp?ID=322

I also had previously saved the ones I was using (V20200110-HC and V20191120-Mount).

And flashing to these "older" firmware and hand controller requires you to also go back to the previous ASCOM Commander 6.331.

Now unfortunately, I don't see that available on the iOptron site.  I do have it saved from before when it was the current version.

Send me a direct message if you don't have it and I can send it to you -- it's about 25MB.

Lamar

[lmcl...@umich.edu]

Hi Jeff,

Here is the link of the archived ASCOM driver and Commander SW:
https://www.ioptron.com/Articles.asp?ID=337

Lamar

[Noah Lambert]

Lamar,

I am very glad to hear that because I plan on running a Edge 925 with a 294MM Pro which is 2350mm FL. Those settings you started, are those like "gospel" or just settings you have come up with? I truly do not understand PHD2 settings and just scape by with my EQ6R-Pro. I also do not know much about the CEM120 because there is not much documentation on it. 

[lmcl...@umich.edu]

Hi Noah,

No the settings are definitely NOT "gospel".  Just values and settings I've learned over the years from others with CEM120s and info from this forum.

The CEM120EC and EC2 apparently did have problems with sending corrections too quickly; supposedly that may have been corrected in the latest firmware.  I don't believe the CEM120 has that issue but since it tracks fairly well, you don't need to be sending corrections very fast anyway.

Lamar

[Noah Lambert]

There is a good chance I will be reaching out when mine comes in! For now, I might just copy those settings you posted as a starting point! 

[J L]

All, I recently received a refurbished CEM120 (non-EC) from iOptron. It came installed with the newest firmware (I believe it's the newest); Mainboard 210605, RA 210420, DEC 210420. Most of the time, I'll see decent guiding (not great guiding, because seeing and wind have both had an impact in the last few weeks). I've been shooting at 540MM focal length (1.44 arc-sec per pixel), and guiding with a 240mm FL guide scope at 3.2 arc-sec per pixel. I haven't had much time at night to fine-tune PHD2 yet, but a few things stick out. 

I've been seeing DEC oscillations (a few times up to ~10 arc-sec peak to peak, but usually less, around 5 arc-sec peak to peak) a few times per night. When they happen, it's usually a few tens of seconds after guiding is started or after dither settles (I use NINA and guide with PHD2). During the DEC oscillation, the RA stays relatively flat, so I wouldn't think it's a wind gust causing the problem. 

Example:  

Additionally, I do see some large DEC excursions (likely due to backlash), but they are not an oscillation. I got the oscillations both with and without PEC turned on. 

Is anyone else using the newest iOptron firmware with the CEM120 (non-EC) and getting these DEC oscillations? 

I saw above that Lamar went back to an earlier version of the firmware... Is that still helping? 

I can post my PHD2 logs if anyone wants to look at them. 

John

[lmcl...@umich.edu]

Hi John,

Yes, going back to the earlier firmware has really helped me to get back to good guiding.  Haven't had a lot of clear nights since I switched back. But the last time it was clear I was getting several 2 hour and longer runs with total RMS of 0.34", 0.39", and 0.43".  And I'm imaging at 2413mm focal length with an ASI174MM Mini on an OAG.

Lamar

[Noah Lambert]

I too have been testing out the CEM120. I normally get guiding at 2350mm with a 174mm on OAG of .5-7" rms. However, last night I could not get below 1.00" to save my life. I really am confused and was hoping tinkering with guiding was over. Here is a night of good guiding 

and here is a night of bad guiding:

most the night the guiding was 1" or above RMS and the peaks were getting very high too

[Bryan]

Noah

How was the seeing on the various nights?

Bryan

[lmcl...@umich.edu]

Noah,

As I mentioned back in the November 9 post, make sure your guide rates are 0.90.  I think yours are still at the default 0.50.  That will help PHD2 to correct more quickly.

And also your first plot was using Predictive PEC for RA, while the second one was using Hysteresis.  Not necessarily anything bad with that, it's just a difference.

And Bryan is right to ask about the seeing.  I've had some nights where guiding can be in the 0.5" to 1.0" and it can almost certainly be attributed to bad seeing.  But fortunately guiding is more times than not below 0.5".  The best you can do is relax the MinMo so you aren't chasing the bad seeing.

Lamar

[Noah Lambert]

Im not sure what the seeing was, but the HFR was pretty large on my images so would go with poor seeing. As for Predictive PEC vs Hysteresis,  I was just testing various algorithms. When I do get bad seeing, is MinMo the only thing to change? I try not to chase my tail by changing various settings. 

[J L]

Lamar, thanks for your response. At least I have some hope that I'll be able to make some corrections, and hopefully get better performance. 

Also, do you PEC programmed into your mount? If so, did it help guiding? 

This afternoon I received this response from iOptron (regarding the DEC oscillation). 

{{{ DEC Guiding:

Those are not oscillation. Most likely caused by meshing of bearing stiction. You try:

1.       Adjust DEC meshing. You may need to release a little bit: https://www.ioptron.com/v/Support/iOptron_Gear_Switch.pdf

2.       Check DEC belt tension when gear switch is engaged http://www.ioptron.us/Support/CEM120_Belt_Tension_Adj.pdf

3.       Increase DEC guiding rate 

4.       Try with turning off DEC fast switching in PHD2 }}}

These suggestions will be fairly easy to implement, so I'll plan to try these first and see what happens. Hopefully I'll get a clear night soon so I can check them out.

If all else fails, I can go back to the prior version of firmware and try that too. 

Thanks,

John. 

On Wednesday, December 1, 2021 at 10:25:25 PM UTC-5 lmcl...@umich.edu wrote:

[lmcl...@umich.edu]

Hi John,

I recently did try making a PEC curve using the trial version of PEMPro.  Once I figured out how to do it and program it back into the mount, I have tried it out only a couple of times since we haven't had any many clear nights recently.  I have enabled PEC and it seemed to work fine with the guiding from PHD2.  I can't say for sure that it has helped with guiding or not; I haven't had a big enough sample size.  I'm thinking it must be helping because when I look at my raw RA in PHD2 Log Viewer I see P-P numbers I never would have gotten before.  For example, on the last night it was clear and with a 2 hour run with total RMS of 0.34", the highest period was at 525.8 seconds and the P-P was 2.6".  At 236.9 seconds (close to the worm gear cycle) the P-P was 2.1".  When analyzing the selected frames, the highest peak was at 134.5 seconds and PHD2 had corrected the P-P down to 0.2"!  All other frequencies were even lower than that!

If you do try it, make sure to enable PEC and let it run for a good long time so the Predictive PEC of PHD2 can fully adjust to it.  Same thing if you then disable PEC -- give the PHD2 guiding routine time to adjust before thinking something is wrong.

I am glad to see iOptron got back with you about the DEC oscillations.  The DEC meshing adjustment document in number 1 seems to be new, with more details of the mechanism used.  I have done that (as I'm sure most CEM120 owners have) and it definitely makes a difference.  Depending on how cold things are, you definitely need to make that adjustment.  I still get some weird noises from the stepper motor/belt in RA when the temperature gets cold.  But it doesn't seem to affect performance.

Number 2 (DEC belt tension) is really involved for RA but not too bad for DEC.  But I would still wait to see if the other three options work first.

Number 3 is definitely recommended; set both RA and DEC guide rates to 0.90 and leave them there.

Number 4 is new to me and intriguing.  I had always wondered if when you get oscillation in DEC if it's simply trying too hard to quickly return so it overshoots.  If I see strange behavior in DEC, I may give that one a try sometime.

Lamar

[Bruce Waddington]

Hi guys.  The last suggestion by iOptron is bogus.  The “fast switch” option only means that PHD2 won’t wait for another 2 guide camera frames after a very large Dec excursion.  It has no effect on the size or number of guide commands that are subsequently issued, it isn’t trying to “go fast” to restore the guide star location   At the point this “fast switch” option is used, the damage has already been done.  If you are using an appropriate MinMove size for Dec – similar or equal to what the GA recommends – there is no danger of changing Dec guiding directions unnecessarily.  If you start fiddling around with guiding parameters with a mount that has poor mechanics, you will almost certainly create a big mess.

 

Bruce

To view this discussion on the web visit https://groups.google.com/d/msgid/open-phd-guiding/7d083a7e-7ae7-4700-9cb7-a480bee9bcc7n%40googlegroups.com.

[lmcl...@umich.edu]

Hi John,

Ross is right from the iOptron group, you're backlash compensation is way too high; 2.685 seconds.  I hadn't noticed that earlier from your screenshot.

My backlash usually is measured around 375ms.  When you run the Guiding Assistant let it also measure your backlash, it should be much less than the 2685ms you have set.  PHD2 will continue to adjust the needed backlash and that can take a few times.  So you can see a small oscillation when it works to dial that in.  But if you start with values closer to correct, it won't take it long and you won't see these large jumps.

And also as Ross mentioned, PEC has nothing to do with DEC, only RA.

Lamar

On Wednesday, December 1, 2021 at 1:06:21 PM UTC-5 jli...@gmail.com wrote:

[J L]

All, thanks for your inputs. As mentioned, I've been chatting over in the iOptron forum, and getting some good suggestions there too. 

I've posted my log files. 
https://openphdguiding.org/logs/dl/PHD2_logs_mSHD.zip

I just took off the DEC motor cover, and the belt seems to be at a reasonable tension. I have no point of comparison, so I hate to mess around with it. It definitely doesn't feel loose. 

In the logs, you'll see that the backlash measured during the two nights where I did guiding assistant were different. Not sure what that means. The optical setup was the same for all three nights (weights and positioning of items on the scope). There may have been minor differences in balance, polar alignment, seeing, and wind. 

When you look at the logs, notice the many DEC "excursions".  Sometimes the DEC corrects quickly, even when changing directions. Other times, all of sudden DEC jumps, and takes many cycles to correct back to zero. 

Even if the DEC issue is fixable, the RA was never "great". Which is definitely disappointing...

 

I'll appreciate and further comments you have. 

Thanks, 

John

[Rick Cohen]

I have a GEM28.  My DEC backlash was over 1 second.  The DEC belt felt pretty tight.  But I went ahead and made it tighter.  I got the backlash down to 350ms.

[J L]

Thanks. You gave me the courage to go ahead and tighten the belt a bit. (and, iOptron told me to do it!)

It's definitely tighter, and the DEC axis slews fine. However, I can't do any measurements of backlash again until I get clear skies. 

Hopefully soon. 

[Antoine R.]

Hi Lamar,

I need your help! I'm responding to this old thread as I am having issues flashing my CEM120 to the older firmware per your instructions.

I got the older firmware from the iOptron website and I am trying to flash it using the iOptron Upgrade Utility v2.23 and it keep saying "Invalid file!". I'm at a loss on how to proceed.

I could not find an older version of the upgrade utility on iOptron website... Could that be the issue?

I did install the previous iOptron Commander driver 6.331 but I cannot communicate with my mount that has the latest firmware.

Thanks!

[lmcl...@umich.edu]

Using the latest Upgrade Utility v2.23 could be the problem.  I don't specifically remember but I always save previous versions of the firmware, Commander, and upgrade utility.  I may have used v2.01 (I see it here on my HDD.)  That was the only other upgrade utility that I have ever had.

You can get v2.03 from this link:  https://www.ioptron.com/v/firmware/iOptronUpgradeUtility.exe

The filename doesn't specifically say the version but it is v2.03.

If that doesn't work, let me know and I can send you v2.01 that I have.  It should be on iOptron website, you just have to search a lot.

Since none of this is directly related PHD2, I don't want to attach it here -- it is only 98K.

Lamar

[Antoine Ribaut]

Thank you very much Lamar. I’ll try this later tonight.

If you could send me directly the firmware in case of have it, you can here : aspe...@gmail.com

Thanks again for your help 👍🏻

You received this message because you are subscribed to a topic in the Google Groups "Open PHD Guiding" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/open-phd-guiding/6lLhd-yKkIY/unsubscribe.
To unsubscribe from this group and all its topics, send an email to open-phd-guidi...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/open-phd-guiding/1ce94d33-b3a7-4c8e-8f00-a74049afe1b8n%40googlegroups.com.