Problem with calibration PHD2 Open PHD Guiding project PHD2 · IvaoSpace_Max · ... · 17 · 691 · 0

Hello to everyone,

I'm writing here cause i have a problem with PHD2.
My setup is composed:

EQ3 OnStep (I know, it's a bad mount, i'm at the limit of paypload for astrophotography but i'm waiting the new mount)
Tecnosky 72/432 FPL53 with reducer 0.8
Player One Uranus-c PRO (2.9 micron)
Ultraguide 32/128
Asi 120MM-S (3.75 micron).

The first light of this setup was on 11 August. The procedure has been:
- stationing the mount
- balance the setup
- Aligniment with NINA
- Point the double Perseo cluster
- Open PHD2, create profile with the focal (128) and micron guide camera, generate dark and i didn't touch any other parameters.
- I chose the star guide e started the calibration –> all ok. A good guided star rounded.

Yesterday i had a terrible night with PHD2!

I followed the same procedure, pointed with NINA the galaxy IC 342, opened PHD2, chose the automatic selected guide star, started the calibration and boooooom…..after the firs step west, the star exit from the box of PHD2 and i got the message "Star lost" then it continued with the other steps and without successfull.

I put a part of the LOG i obtained.The focus was enough, i used the tool inside sharpcap….(If you need a full log, i can upload it)

"Calibration Begins at 2024-08-22 22:11:56
Equipment Profile = test
Dither = both axes, Dither scale = 1.000, Image noise reduction = none, Guide-frame time lapse = 0, Server enabled
Pixel scale = 6.04 arc-sec/px, Binning = 1, Focal length = 128 mm
Search region = 15 px, Star mass tolerance = 50.0%, Multi-star mode, list size = 12
Camera = ZWO ASI120MM, gain = 48, full size = 1280 x 960, no dark, defect map in use, pixel size = 3.8 um
Exposure = 2000 ms
Mount = On-Step (ASCOM), Calibration Step = 1700 ms, Calibration Distance = 25 px, Assume orthogonal axes = no
RA Guide Speed = 15.0 a-s/s, Dec Guide Speed = 15.0 a-s/s
RA = 3.82 hr, Dec = 68.1 deg, Hour angle = -8.68 hr, Pier side = West, Rotator pos = N/A, Alt = 27.8 deg, Az = 18.8 deg
Lock position = 1232.268, 210.654, Star position = 1232.268, 210.654, HFD = 4.74 px
Direction,Step,dx,dy,x,y,Dist
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
INFO: STAR LOST during calibration, Mass= 0, SNR= 0.00, Error= 2, Status=Stella persa per SNR basso
Guiding Ends at 2024-08-22 22:12:56"

I'm not expert with it, but i didn't change nothing from the first night so i was confidant that all was ok. (The only difference between yesterday and the last time are the dark, yesterday  i didn't take!)
If i active the camera with sharpcap i can see more stars than PHD2…..

If you need other information, let me know ;)

Thanks for the help!
Massimo

In this scenario, I would have suggested simply re selecting a guide star which will likely result in PHD2 picking a star closer to the center of the frame, then redoing the calibration.

I would try to "unbalance" the mount a bit. In DEC the backlash could be to big to handle for PHD2. I had to do this with my HEQ-5.

Hi Massimo! I too sometimes find PHD2 a little unforgiving at times, especially when the atmosphere is very turbulent. A few more steps to try:
- in addition to using the calibration routine with your scope pointed close to Dec~0deg.
- check and research any calibration error reports. I had a problem with Dec backlash due to a loose worm gear - PHD2 helped me find that (my mount is different from yours, but also could be suspect).
- make sure your guide scope/asi120mm are in good focus.
- maximize FWHM as much as possible. Dependencies: focus, seeing/atmospheric turbulence.
- are your guide scope and imaging scope focal ratios about the same? If the f-ratio of your imaging scope + reducer are significantly different from your guide scope, then this might cause tracking issues.

That’s all I can offer. But don’t give up! There’s a solution to every problem - it just hasn’t yet been found!

I really do not think the problem here is your mount. Your mount is very possibly inadequate - but this is not what is causing the problem you have described here. From the log, it is simply that PHD2 is choosing a star too close to the edge of the frame. Depending on the angle of the guide cam with respect of the RA and DEC movement, this can sometimes cause the star to move out of the frame during calibration. This is what is happening here, and evidence that your mount is not the problem is given by your statement that you had a successful run the night before with the same setup.

If you are trying again today, I suggest the following. Run Calibration Assistant:

https://openphdguiding.org/man-dev/Tools.htm#Calibration_Assistant

Click on the Slew Button, the scope with then slew to the optimal location for calibration. Then click calibrate. PHD2 should successfully calibrate (assuming that where the scope slewed to has open sky not blocked by trees or buildings). Note: It is important to NOT change the orientation of the guide camera after calibration, either directly or through rotating the focuser if using an OAG.

Slew to your imaging location, then run Guiding Assistant:

https://openphdguiding.org/man-dev/Tools.htm#Guiding_Assistant

Ensure "Measure Declination Backlash" is checked. This will likely take several minutes, but Declination Backlash need not be measured every session. Accept the recommendations for guiding parameters (including backlash compensation) made by the program.

You should now be good to go. Let us know how this goes. There may be specifics  around Declination Backlash for your mount that are different than what Guiding Assistant provides, but it is a good starting point. As others have stated, the PHD2 forum is a good place to post technical quesitons.

Massimo let me stress the point that you have to calibrate close to the crossing of the meridian with the celestial equator, NOT anywhere in the space. If you use the calibration assistant, as suggested by Aron above, you are forced to do that.
Secondly: if you have not changed the position of the guide scope vs the main tube, you do not have to re-calibrate each night.

Ciao, Mau

Hello to everyone!

Thanks for the other advices, so appreciated!
Yesterday I had another little session to check the problem.

Firstly, i optimized the focus of the guide camera. I positioned  the scope in one place where I was able to point to dec=6,5° and RA=20.26h.

With calibration assistant, it started well the process (Little victory). I mean that i didn't get the error "STAR LOST" so for me it's an improvement.
But now, during the calibration (Maybe during West steps or East Steps) i get the message 

"The guided is failes, because the scope is starting to move"
This is translated in the log in this way:

"Calibration Begins at 2024-08-23 23:50:58
Equipment Profile = AstroMax_128
Dither = both axes, Dither scale = 1.000, Image noise reduction = none, Guide-frame time lapse = 0, Server enabled
Pixel scale = 6.04 arc-sec/px, Binning = 1, Focal length = 128 mm
Search region = 15 px, Star mass tolerance = 50.0%, Multi-star mode, list size = 12
 Camera = ZWO ASI120MM, gain = 90, full size = 1280 x 960, have dark, dark dur = 2000, no defect map, pixel size = 3.8 um
Exposure = 2000 ms
Mount = On-Step (ASCOM), Calibration Step = 850 ms, Calibration Distance = 68 px, Assume orthogonal axes = no
RA Guide Speed = 15.0 a-s/s, Dec Guide Speed = 15.0 a-s/s
RA = 20.26 hr, Dec = 6.5 deg, Hour angle = 0.60 hr, Pier side = West, Rotator pos = N/A, Alt = 51.9 deg, Az = 194.6 deg
Lock position = 297.383, 216.588, Star position = 292.752, 216.740, HFD = 3.96 px
Direction,Step,dx,dy,x,y,Dist
West,0,0.000,0.000,288.016,216.171,0.000
West,1,4.380,0.444,283.636,215.726,4.402
West,2,9.340,0.826,278.676,215.345,9.376
West,3,13.986,1.081,274.030,215.089,14.028
West,4,18.846,1.384,269.170,214.787,18.897
West,5,23.468,1.494,264.548,214.677,23.516
West,6,28.140,2.242,259.876,213.929,28.229
West,7,32.758,2.457,255.258,213.714,32.850
West,8,37.176,2.890,250.840,213.280,37.288
West,9,42.149,3.159,245.867,213.012,42.268
West,10,46.923,3.436,241.093,212.735,47.049
West,11,51.564,3.926,236.452,212.244,51.714
West,12,56.117,3.991,231.899,212.179,56.259
West,13,60.745,4.452,227.271,211.719,60.908
West,14,65.683,5.389,222.333,210.782,65.903
West,15,70.020,5.782,217.996,210.388,70.259
West calibration complete. Angle = 4.7 deg, Rate = 5.510 px/sec, Parity = Odd
East,6,70.020,5.782,217.996,210.388,70.259
East,5,74.983,6.135,213.033,210.036,75.234
East,4,79.410,6.365,208.606,209.806,79.665
East,3,84.366,6.403,203.650,209.768,84.609
East,2,88.837,6.902,199.179,209.268,89.104
East,1,93.621,7.301,194.395,208.870,93.905
East,0,98.552,7.668,189.464,208.503,98.850
Backlash,0,0.000,0.000,189.464,208.503,0.000
Backlash,1,4.464,0.292,184.999,208.212,4.474
Backlash,2,9.407,0.810,180.057,207.694,9.442
Guiding Ends at 2024-08-23 23:51:47
INFO: SETTLING STATE CHANGE, Settling failed"

Maybe the problem is some parameters that need to be modified?
Now i write also in PHD2 Forum maybe other person.
So today, i'm going to have the third round !

Massimo

Hi everyone!
great news finally! Calibration done 😁💪🏻!

Excellent news and so happy for your success!

Calibration step size is too high my guy. Go back into phd2 settings, make sure your scope details are correct and reset. Should return a value under 1000ms.

Enjoy!