Curious about how this is happening.

[Kenn Hopkins]

Each time I run the Guiding Assistance I start by checking ‘Clear mount calibration’ then I calibrate on a star that is close to Meridian and 0 declination – East side of Meridian.

On the 3^rd of September I performed a Drift Alignment until there was no star movement for DEC and RA for 15 minutes. I then did a PHD2 Guiding Assistance and received a Polar Alignment Error of 3.4 arc-min with Right Ascension RMS of 0.18 arc-sec and Declination RMS of 0.10 arc-sec. guiding was OK.

September 6 I again ran a Drift Alignment until there was no star movement for DEC and RA for 30 minutes. I then did a PHD2 Guiding Assistant and received a Polar Alignment Error of 1.4 arc-min with Right Ascension RMS of 0.32 arc-sec and Declination RMS of 0.13 arc-sec.

I would have thought the guiding would be better with a longer Drift Alignment, but it seems to of produced result that were not as good. Even the guiding was poor with oblong stars. I use a Losmandy Titan Mount with a C-8 HD imaging scope and 80mm guide scope.

Kenn

[Brian Valente]

Kenn

Please upload your logs for the timeframe you are asking about

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

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Brian Valente

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[Kenn Hopkins]

Following is the link for the log files: https://openphdguiding.org/logs/dl/PHD2_logs_FrX6.zip

Kenn

[Brian Valente]

Kenn

If polar alignment was the issue, then I would expect improving PA would result in improved guiding. However looking at your logs, the constraint to guiding performance is really in the periodic error of your mount

Your overall guiding RMS is low, but RA is higher than Dec. 

Here are a few things I see can can improve your guiding:

1. I would change your PPEC period to 159 seconds, increase your control gain to 0.7 and your prediction gain to 0.8. I realize you have it currently set to 32sec. I don't see anything that suggests it's an issue, but keep an eye on it

2. enable dec backlash compensation. start with a value of 600 and set the max value to 1200ms

I am not sure what version of the Gemini 2 controller you are on, but that 159 second period shoudl be easily addressed by using PEMPro for a mount-based PE correction and the latest L6 firmware 

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/c871f957-07b4-4cba-89f9-e7b091047707n%40googlegroups.com.

[Kenn Hopkins]

10,000 years ago you assisted me with PemPro for my Titian mount and also suggested the following.

I regret but I do not see  PPEC period to 159 seconds, increase your control gain to 0.7 and your prediction gain to 0.8

Kenn

[Brian Valente]

Kenn

yes, you seemed familiar ;)

that 31.9 second error may have worked itself out, but it's worth testing some new settings

Look at this suggestion for revised PPEC

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/d8c567a8-7272-48ef-8958-17e338f242b4n%40googlegroups.com.

[Kenn Hopkins]

Weather will not cooperate for the next few nights but I will try as soon as it is clear to try these different settings.

You have a different setting for Declination, should I try those also?

I ran the Train PEC last night but will also need to wait until a clear night.

Last time I ran PemPro all I received was error messages because of  PemPro not working with ZWO Products, according to PemPro.

I need to install the latest version.

Anyway I will let you know what happens next imaging session.

Appreciate your time.

Kenn

[Brian Valente]

Kenn

do not make any other changes to PPEC or anything else on that screen other than what's pointed out

ZWO products absolutely do work with PEMPro, and you should use PEMPro for high quality PEC.

Just recording it via keypad is probably not going to produce a good PEC for precision imaging. You probably just need to bin your camera in PEMPro, but please take that up over at the PEMPro support forum

Brian

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/d2786ce1-82d8-4483-8666-98f7e96df58fn%40googlegroups.com.

[Kenn Hopkins]

If I may ask a question:

Back in 2018 you suggested I change the Period Length (in the Predictive PEC) to 31.9 but now in 2025 you are suggesting I change it to 159. Has something changed from 2018 to 2025?

I had a 1.5 hours window (9/10/2025) the other night and I entered the changes you suggested and ran the Guide Assistance in PHD2. I did get a better RA RMS of 0.14 px arc-sec and DEC of 0.06 but the Polar Alignment Error was 5.2. On the 7^th having the Period Length of 31.9 the RA RMS was 0.19 and DEC of 0.08 with a Polar Alignment Error of 1.4 arc-min. I have my Titan tripod embedded in cement and I cover it with a Telegizmo cover.

I’ve noticed that even when I run Guide Assistance on the same night the Polar Alignment Error changes each time, even on the same night. Is this normal?

I need to somehow get the RA RMS closer to the DEC RMS in order to obtain round stars. Would PEMPro help with that?

As soon as I get a clear night, I will run PEMPro and see what happens. I will try and update this posting with the results.

Again I really appreciate your time.

Kenn

[Brian Valente]

Hi Kenn

>>>Has something changed from 2018 to 2025?

based on your last logs, it appears yes

>>>>I had a 1.5 hours window (9/10/2025) the other night and I entered the changes you suggested...

please upload those logs, i would need to look at the details

>>>I’ve noticed that even when I run Guide Assistance on the same night the Polar Alignment Error changes each time, even on the same night. Is this normal?

yes, although keep in mind PA in PHD is an estimate. there are other factors that can change it such as flexure. I would not stress about PA too much unless it shows up as negatively affecting your guiding. your Dec RMS is lower, so it's not a constraint or issue

>>>I need to somehow get the RA RMS closer to the DEC RMS in order to obtain round stars. Would PEMPro help with that?

A lower periodic error (e.g., using PEMPro) will likely reduce RA RMS if it's periodic, and iirc yours has a good bit of that. Remember you will need the latest Gemini L6 firmware to get a good PEC

Brian

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