Interpreting calibration diagram from PHD2 log viewer

[StuartT]

Can anyone explain what this is telling me? I can't seem to find any documentation on this (Andy Galasso's Analysing PHD2 guiding results doesn't include calibration)

Thanks

[The Admiral]

That would be useful to me too!

Ian

[michael8554]

Hi Stuart

1. Those dozen or so lines in the GuideLog are setup info - which items would you like explained  ?

The graph shows outward steps as blue W1, W2 etc, and red N1, N2 etc.

These should ideally be evenly spaced, groups of pairs show backlash and/or stiction.

Bunching at the start of the N run would show you hadn't cleared Dec backlash before staring the Cal.

And the faster return steps are colourless E4 to E0 , and N4 to N0.

2. But for info on how effective the Cal was, you should look at the report at the start of the next item in the GuideLog,  "Guiding begins at......... "

Michael

[StuartT]

6 hours ago, michael8554 said:

Hi Stuart

1. Those dozen or so lines in the GuideLog are setup info - which items would you like explained  ?

The graph shows outward steps as blue W1, W2 etc, and red N1, N2 etc.

These should ideally be evenly spaced, groups of pairs show backlash and/or stiction.

Bunching at the start of the N run would show you hadn't cleared Dec backlash before staring the Cal.

And the faster return steps are colourless E4 to E0 , and N4 to N0.

2. But for info on how effective the Cal was, you should look at the report at the start of the next item in the GuideLog,  "Guiding begins at......... "

Michael

Apologies. I shouldn't have included the text. I was meaning the diagram. Thanks for explaining. Does it matter that the red and blue lines are not aligned with N and W? does that rotation just indicate that my guide cam is rotated relative to the meridian and equator?

[michael8554]

PHD2 doesn't mind if the guidecam isn't oriented with N/W.

It all gets accommodated by the Cal.

The red and blue lines not a 90 to each other is a problem called Orthogonality.

If it's too far out PHD2 will advise.

Michael

 

[geoflewis]

Do these links to PHD2 documentation about calibration help...?

https://openphdguiding.org/man/Basic_use.htm#Automatic_Calibration

https://openphdguiding.org/man/Tools.htm#Calibration_Details

[knobby]

@StuartTAre you using an off axis guider ? as your focal length in PHD2 looks about correct for a 150ED / Reducer.

Focal length in PHD2 should be of the guide scope.

[The Admiral]

14 hours ago, michael8554 said:

The red and blue lines not a 90 to each other is a problem called Orthogonality.

If I may hijack the thread, can I ask whether this is allied to the mount itself, and therefore not correctable, or is there something in the set-up that causes this? For that matter, does it matter?

Ian

[StuartT]

19 hours ago, geoflewis said:

Do these links to PHD2 documentation about calibration help...?

https://openphdguiding.org/man/Basic_use.htm#Automatic_Calibration

https://openphdguiding.org/man/Tools.htm#Calibration_Details

Thank you! Yes they do. 

19 hours ago, knobby said:

@StuartTAre you using an off axis guider ? as your focal length in PHD2 looks about correct for a 150ED / Reducer.

Focal length in PHD2 should be of the guide scope.

Yes, I am using an OAG. Hence I used the FL of the scope (and reducer - which is spelled incorrectly in the profile 🤣)

[knobby]

8 hours ago, The Admiral said:

If I may hijack the thread, can I ask whether this is allied to the mount itself, and therefore not correctable, or is there something in the set-up that causes this? For that matter, does it matter?

Ian

Not 100% sure but I know poor polar alignment can cause the non 90 degree appearance as can backlash.