GUIDING ANOMALIES

[David Miller]

In general, my guiding seems fairly good, usuallyjust a fraction of a pixel compensation (though SNR is never very high)  but the graph shows a vast number of short dips and peaks and I'm curious what I can do to improve this, or if I even need to. The log is attached - I tried to upload a log file but the two from last night did not appear in the list. Is there some way to find them or is this txt file adequate? Thanks for any suggestions. -dm

[Brian Valente]

Hi David

we'll need to see a guidelog, not a debug log

You can open the log folder from PHD's menu and you should see what's available there, but it's best to use the built-in log uploader

https://openphdguiding.org/getting-help/

Brian

On Mon, Dec 13, 2021 at 12:56 PM David Miller <dhay...@gmail.com> wrote:

In general, my guiding seems fairly good, usuallyjust a fraction of a pixel compensation (though SNR is never very high)  but the graph shows a vast number of short dips and peaks and I'm curious what I can do to improve this, or if I even need to. The log is attached - I tried to upload a log file but the two from last night did not appear in the list. Is there some way to find them or is this txt file adequate? Thanks for any suggestions. -dm

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Brian Valente

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[David Miller]

Okey doke - here is a link to tongit h's session: https://openphdguiding.org/logs/dl/PHD2_logs_CyPB.zip

Happy to entertain any suggestions and thanks for the help.

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[Bruce Waddington]

Hi David.  Can you give us some info on your overall setup?  Are you guiding with a separate 550mm focal length refractor or are you using an OAG?  What is your main imaging scope?  This is critical to interpreting your guiding results.  You’re working with a calibration that is 5 months old and looks like it was done with a different guide speed setting in the mount.  So you should fix your EQMOD settings to match this document:

 

https://github.com/OpenPHDGuiding/phd2/wiki/EQASCOM-Settings

 

Then do a fresh calibration and send us a log with some 15-20+ minute guiding sessions using the new calibration with no adjustments to any of the parameters.  The guiding tests should be run near Dec=0 and at least 45 degrees above the horizon.

 

Regards,

Bruce

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[David Miller]

OK, will do that next clear night. My setup is a Skywatcher Esprit 100 ED on a Skywatcher AZ-EQ 6 Pro mount using an ASI290mm mini as a guidescope. EQMOD, ASCOM, Sequence Generator Pro, PhD2...More to follow.

Thanks,

Dennis

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[mj.w...@gmail.com]

Hi Dennis

"using an ASI290mm mini as a guidescope. "

The  ASI290mm mini  is a guide camera.

As Bruce requested, what focal length guidescope are you using ?

Michael

Wiltshire Uk

[David Miller]

Whoops - sorry about that - (late night). It's a 50mm Televue scope. The biggest question for me is whether the peaks and dips in the log/graph are issues of concern. I just integrated the work from the other night and it looks reasonably decent... my processing skills will be the big limitation here. So how do I know if I actually have a problem or actually can get superior results? I don't have enough experience to know that what I get could be better... 

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[Bruce Waddington]

Hi David.  We don't seem to be making any progress here.  We're asking what is the FOCAL LENGTH of the guide scope - not the main scope but the guide scope.  You've said it's a 50mm Televue scope but I can't find such a thing on the web so I can't know what its focal length is.  You'll have to tell us what that number is - don't guess at it, we need to get it right.  We're pounding on this because the guiding results don't look particularly believable to me, suggesting that you've perhaps mis-configured the focal length setting in the PHD2 profile and the reported results aren't right.

Bruce

[David Miller]

Sorry - my lack of experience. Stellarvue 50mm guide scope

210 mm https://www.stellarvue.com/1-50-mm-photographic-guide-scope-black/

Thanks for the follow-up.

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[bw_msgboard]

Hi David.  Ok, this is what I suspected.  When you set up your PHD2 configuraton profile, you said the guide scope focal length was 550mm - I don't know why you did that.  If the correct focal length is 210mm, that means the guiding/tracking errors in the log are being under-reported by a factor of 2.6x.  I think you need to start over and do some baseline testing to determine how your mount is actually behaving.  That will mean going about things carefully and methodically, starting with setting the EQMOD settings according to this document:

 

https://github.com/OpenPHDGuiding/phd2/wiki/EQASCOM-Settings

 

Then you need to create a new PHD2 profile with the correct settings - notably the correct focal length - using the new-profile-wizard.  The best approach is to follow the steps in the document:

 

https://www.dropbox.com/s/os1thorvswmzaul/How%20to%20create%20a%20baseline%20for%20guiding%20results%20using%20OpenPHD2.pdf?dl=0  

 

Once this is done, your subsequent guide logs can be analyzed correctly and we can probably answer your original questions.

 

Good luck,

Bruce

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From: open-phd...@googlegroups.com [mailto:open-phd...@googlegroups.com] On Behalf Of David Miller

Sent: Wednesday, December 15, 2021 4:07 PM

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[David Miller]

Great, Bruce - thanks for the info. I could see something was up but didn't catch the bad configuration. The only question I have is whether my guiding for my imaging sessions has actually been bad or bad enough to impact my sequencing, The image I captured at 180 x 30" exposures this week was quite nice. But maybe better guiding will allow me to use longer exposures - 120" is about the max to date. So that will really be the big issue when I redo the settings.

Thanks again for staying up on this and for the suggestions. Very helpful indeed. -d.

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[David Miller]

Things fairly well blew up this week. Logs are here:

https://openphdguiding.org/logs/dl/PHD2_logs_kh23.zip 

I tried to follow the suggestions given to me and started with modifications to my EQMOD settings. I couldn't find all of the parameters that were recommended on the documents. EQMOD interface photo is attached IMG_7461

So then I tried to calibrate and I got a repeated message that I did not have enough steps. I used the Mount setup area and changed the steps from 600 all the way down to 20 - on several occasions, when I changed the value in the Calculator (second) window, the value in the Guider Settings for Cal step did not change. With a value of 20 I still got the error message "not enough steps" - the max I could get was 4, so the calibration was probably not successful. (see IMG_7464, which shows the original error).

When I did accept the calibration, I got additional error messages, including one that said RA and DEC angles computed are questionable (IMG_7473), but there were no suggestions about how to correct this - how would I correct this?

Finally, when all was said and done, I got an error saying PulseGuide command to mount has failed (IMG_7464), even though the mount was unparked and all the cables were fine and I was able to move the mount manually using EQMOD. I could not detect any error. 

At this point, the values are pretty terrible and I don't know if I could guide at all. A shame, with two clear nights ahead. 

My goal is to be able to guide up to 3 or 4 minutes - equipment is Skywatcher AZ-EQ6 Pro, so I believe that is possible. Would really appreciate any help - this is Priority One on my en,.  

Thanks much

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[Dennis Miller]

Sorry - here's the pulse guide error...

[Brian Valente]

Hi David

Your calibrations are still not good, so your guiding results are going to be compromised until you sort this out

a quick look at your guidelogs here's what i see:

- your mount guidespeed is still all over the place. your rates for RA and Dec should be around 7-15, and you are at 55. If you aren't clear on how to proplery configure your mount or EQMod, i suggest you contact one of the relevant user groups to do this.

- You should not be manually adjusting the step size or # of steps. this is calculated for you. If it's not producing the correct results, it's pointing to a problem elsewhere that you need to address (likely the guidespeed issue mentioned above)

Despite these issues, your two long-ish guide runs from 12-19 seem perfectly reasonable with total RMS around 1.15". 

If you enable dec backlash compensation it should improve a bit more. 

Given your image scale (at least for the guider) this should give you relatively tight and round stars. Was that the case?

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[Dennis Miller]

Thanks very much for the info, Brian. Very much appreciated. 

 

- your mount guidespeed is still all over the place. your rates for RA and Dec should be around 7-15, and you are at 55.

* I thought the correct DEC and RA speeds were supposed to be somewhere above .5, up to around .8 or .9... Are you referring to the ASCOM PulseGuide Rate value that is set in EQMOD? 

 

If you aren't clear on how to proplery configure your mount or EQMod, i suggest you contact one of the relevant user groups to do this.

*I'm just not clear which problems need to be addressed in which software - I can get around both PhD and EQMOD, but not sure where to perform the corrections that PhD is suggesting... DEC/RA axis angles, for example. 

- You should not be manually adjusting the step size or # of steps. this is calculated for you. If it's not producing the correct results, it's pointing to a problem elsewhere that you need to address (likely the guidespeed issue mentioned above)

* I tried to change the step size because I was getting the error The calibration was done with a very small number of steps... Consider Reducing the Size of the Calibration Step. I assumed I needed to lower the step manually. Isn't that correct?

 

Despite these issues, your two long-ish guide runs from 12-19 seem perfectly reasonable with total RMS around 1.15". 

* Things crashed following those 12/19 runs when I tried to do the calibration. So  I think I am in much worse shape at present.

If you enable dec backlash compensation it should improve a bit more. 

* Will try that tonight.

Given your image scale (at least for the guider) this should give you relatively tight and round stars. Was that the case?

* I have had success before 12/20 with decent guiding, but at the moment, I'm not sure what I will get. Will try tonight.  

Also, any idea why a PulseGuide command would fail if all cables/etc. are secure? And would I adjust the RA and DEC axis angles in EQMOD? I'm not connected right now so I can't check if there are settings for those - would you happen to know?

Thanks again and best for the holidays.

-d.

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[mj.w...@gmail.com]

Hi David

To add to what the experts said:

You finally got a normal looking Calibration on your final Cal attempt at 21:13.

It only took 4 steps instead of 12, but that was with a different Equipment profile "Equipment Profile = esprit" - did you swap equipment during these sessions ?

Very confusing.

Try again with the esprit profile,  but with the PHD2 Calibration Step Size back from 5000, to 600 that PHD2 had calculated with the earlier equipment profile NEW PHD 12_21

Or if NEW PHD 12_21 was with different equipment, best to start yet another Equipment Profile with the correct settings.

Your EQMOD ASCOM Pulse Guide Setting in your screen grab is x0.70 which seems sensible to me. 

But you have the mount guidespeed set to only "RA Guide Speed = 4.5 a-s/s, Dec Guide Speed = 4.5 a-s/s,"

Needs to be at least 7.5 as/s as Brian stipulated.

Michael

Wiltshire UK

[Dennis Miller]

Thanks very much, Michael. Sorry, but where are you seeing the RA Guide Speed = 4.5 a-s/s, Dec Guide Speed = 4.5 a-s/s," setting and/or where do I adjust that?

I started a new profile as part of the calibration as recommended here... I only have the one mount, the AZ-EQ6 Pro... (Esprit is my OTA...) Confusing for sure... 

Will start over tonight but,I'm not clear how/where to make a few of the adjustments recommended by PhD including the RA/DEC axis angles or why I would get the PulseGuide command failed message... . I posted a note on the EQMOD forum and will see what transpires.

Thanks again.

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[mj.w...@gmail.com]

Hi David

Apologies, I was looking at your logs in time order, I didn't notice the dates were different, so my replies were rather erroneous I'm afraid.

To correct myself:

NEW PHD 12_21 had a mount guide speed of RA Guide Speed = 10.5 a-s/s, Dec Guide Speed = 10.5 a-s/s      -    that's good.

And Calibration step size was Calibration Step = 600 ms,      -    stick with that if your inputs to the Equipment Profile  were correct.

But the measured rates were still high  Norm rates RA = 56.8"/s,  Dec = 56.9"/s;  that could be the EQMOD ASCOM PulseGuide Setting too high, or a setting in SGP ?

Michael

Wiltshire UK

[Dennis Miller]

Thanks for the update, Michael. I'm still challenged by some of the errors/values for which I don't know the fix. For example, I am at a loss how to modify the RA and DEC axis angles, which PhD reports are very much out of wack... I haven't found a setting in either EQMOD or PhD. Also, as noted earlier, when I tried to do the calibration, PhD reported that it completed the cal, but only using too few steps, so it suggested I change (lower) the step size. I moved it from 600 all the way down to 20 in steps and I still only got 4 steps with the cal. Is that good enough? And can PhD save multiple profiles with different calibrations, or only revert to the most recent one? I'd like different settings without risking any good data that I might have in the profile.... 

I also received an error that PhD could not send a GuidePulse, that the rates for RA and Dec should be around 7-15 but are at 55 (from Bruce), etc.) - just a slew (no pun intended) of problems that I don't know how to correct. If/when you have a moment, I'd like to get your advice (or that of others) on this.  I'm pretty sure my current settings are a showstopper until I get this sorted.

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[Brian Valente]

Hi Dennis

>>>For example, I am at a loss how to modify the RA and DEC axis angles, which PhD reports are very much out of wack... I haven't found a setting in either EQMOD or PhD.

You don't directly modify the orthagonality angle. Instead, it's a resulting measure of other problems in your setup. 

During calibration, all the measurements are strictly in the camera coordinates because PHD doesn't know yet how to map those into the RA and Dec axes.  So when PHD is issuing calibration guide steps on one axis or the other, it has to assume that the guide star movement it sees is a reaction to those commands and the movement is along the axis we’re measuring.  In other words, it assumes the guide star will mostly “stand still” on the other axis.  Obviously, this can’t happen exactly, which is why PHD tries to move the star a long distance in a short time on the axis it's measuring.

In that case, the unwanted movement on the “other” axis should be substantially smaller and will have minimal effect.  For mounts that are working at all, the measurement of the RA axis orientation should be fairly accurate because the Dec motor isn’t running at all.  But if the polar alignment error is huge, there could still be large drift in Dec that will be interpreted as RA movement.  Conversely, if PHD is trying to measure the Dec axis orientation and the mount has a giant periodic error, some part of that error will be interpreted as Dec movement.  In other words, tracking errors on one axis can “bleed” into the measurement results for the other axis.

Common causes of orthogonality errors are
bad polar alignment,
large declination backlash, or
large periodic error in RA.

In your case, it may be one or more of the above, but your measured guide rates are so out of whack, it's hard to know what is going on. I suspect EQMod or your mount driver may not be configured correctly (or both). I really think you should be taking this to EQMod user forums to sort out your guide rates.

>>>Also, as noted earlier, when I tried to do the calibration, PhD reported that it completed the cal, but only using too few steps, so it suggested I change (lower) the step size.

I'm not sure what "it" you mean by "it suggested you change the step size". In your case, i would not be fooling with the step size. something else is causing too few steps, likely the overly fast guide rate (in the neighborhood of 50as/s as I recall?) 

I think once you sort that out, everything else should fall into place

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[Dennis Miller]

Thanks, Brian. Clear night tonight so I am back on the case.  I have posted this stuff at the EQMOD forum and am trying to collect the info from both here and there. Want to focus on a few things for tonight.

1. I plan to do a new profile after using Drift Align to correct PA. Is there a PA accuracy value/threshold that PhD is happy with? I believe the PA accuracy shows up in the Guiding Assignment results, correct?

2. I want to be clear on where to modify the "measured guide rates..." Are those the ASCOM Pulse Rate Settings? If not, are the measured guide rates settings that I can control or are they just shown as the result of one of the processes I performed in PhD? What would suitable values be for PhD guiding?

3. After drift aligning. I'll do a calibration, then a guiding assistant, then enable Predictive PEC (from Bruce's video talk) to try and get back in business. If there is anything else specific that you can recommend, please let me know.

And thanks very much for your help... Much appreciated. 

-D.

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[David Miller]

I think I have crossed the threshold into decent guiding... Started with a manual drift align, then a calibration, then a Guiding Assistant, and my session went fairlyy well. Best SNR I have ever seen (what is the "ideal range"?) and very low .2 - .5 pixel adjustments, although the graph looked very active.  

Log is posted here https://openphdguiding.org/logs/dl/PHD2_logs_hmB3.zip    

and I would be very curious for any suggestions or just a general response to what anyone finds there.  

One thing - I built a dark library during the calibration and when I quit PHD it told me that the dark library did not match the guide camera... I only had the guide camera connected when I did the calibration, but I do have two ASI cameras... not sure what that message was about or if I had already disconnected the guide camera when the error was reported. I did not see it during the guiding session - when does PhD2 access the dark library? And on a side note, when it is dtaking darks, since I can;t cool the guide camera, does it matter that it might be warmer when I satrt and build the library than it is during the next few hours while guiding?

Huge thanks for all the help.
-D