Setting for EQ8r to improve RA Guiding

[sirharry3921]

Hi there,

I did recently upgrade from my AzEQ6 to an EQ8R Mount.

While I had on the "6" constantly arount 0,6" guiding accuracity, I face some problems getting better results with my "8" especially with RA axis (same equipment loaded around 15kg, OAG with 10" carbon newton).

I tried almost every combination of MinMo, agressivity pulse and hysteresis.

The shown values have been the best I could optimise.

I guess there is room for improvement, can you give me a hint please?

Most recent log is here:

https://openphdguiding.org/logs/dl/PHD2_logs_UfzN.zip

Thx in advance

Harald

[Brian Valente]

Hello Harald,

Looking at your longest run of 1 hour 18 minutes (segment 21), your RA is the primary constraint to lower guiding at a total of 0.73" RMS, or about 2x what Dec is reporting

the largest contributor to this is around 200 seconds, this is the uncorrectable residual error (in other runs it's around 202 seconds)

I suggest you try PPEC algorithm for your RA with the settings shown below. That should help quite a bit

In addition, fpr Dec decrease your min move to around the same as RA 0.4 and make sure your dec backlash compensation has large enough max, i pointed out two settings that should work for you there.

FYI on that same run (pier side East) it looks like all corrections in dec are in one direction (south), which suggests something has shifted in your equipment. you should check that out and ensure everything is tight, watch for it in future

Brian

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Brian Valente

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[steve]

Hi
EQ8r: We use PPEC for RA with a fixed period of 198 which corresponds to the worm period.
Works well.
HTH and CS

[Bruce Waddington]

I suspect you have more basic problems, not just tweaks to settings, so I will offer some additional comments.  Overall, you were getting way too many lost-star events, assuming you weren't working with cloudy skies.  When guide stars were found, they often had HFD values of 7 or 8 pixels.  That suggests to me that perhaps the guide camera isn't well-focused on the OAG.  That said, things were better in the middle of the session, so I don't know what happened.  You're also continuing to use a calibration that produced very poor results.  Did you use the Calibration Assistant for that?  You need to use it every time you calibrate and if you can't get a result that is at least 'acceptable', you're not likely to have much success guiding.  It sounds like you made the common mistake of thinking that changing a bunch of guide algorithm parameters - somewhat wildly in your case - would somehow fix your problems.  It won't, your problems are with the your gear.  You should start over with a new PHD2 profile and leave all the algorithm parameters alone - including the use of ResistSwitch on Dec.  I recommend that you bin the guide camera to improve your ability to get usable stars - this will not impact your guiding results.  As you did before, set the 'reverse dec output after meridian flip' option to true, that is definitely needed for the GSServer driver. Then concentrate on getting a sharp focus of the guide camera using whatever tools will give you quantitative feedback on focus - the Star Profile tool, SharpCap, whatever. It looks like this may be your first experience with an OAG, so the initial focusing can be tedious - but it's critical and should only need to be done once.  Then use the Calibration Assistant and work to get an acceptable or good calibration.  Don't ignore calibration alerts and poor results, they will come back to bite you.  Problems with the computed "rates" for example, point directly to problems with the mount. Then run the Guiding Assistant in that same sky location and let it make recommendations for appropriate min-moves - don't pick numbers out of the air.  Let it run the Dec backlash test and accept its recommendations.  Even if the GA produces a result that over-estimates backlash, that will quickly be corrected once guiding actually starts.  If you do all this, you should look for smoother guiding results with no lost stars.  At that point, you can try using PPEC for RA guiding while setting the period length to the worm period as suggested earlier.  In your case, you were operating with a measured RA calibration rate that was barely 1/2 of what it should be, so PPEC isn't going to work well until that's fixed.

Good luck,

Bruce

[Michael Waring]

Hi Harald.

I noticed you have different RA and Dec guide rates set in the mount :

RA Guide Speed = 10.5 a-s/s, Dec Guide Speed = 12.0 a-s/s, Last Cal Issue = Rates,

Michael

Wiltshire UK