PHD Calibration advise - Help Please

[AlistairW]

Hello,

I (think) I am having issues with PHD2 calibration. First some background ....

- Polar alignment is about 1 arc-minute

- Balance of OTA is good. (80mm frac on HEQ5).

I get PHD2 to select a candidate guide star (p.s. I have a dark library on my guide camera a QHY5l-II), I then select calibration. I have a 210mm FL guide scope and have allowed the brain to calculate the steps (about 1150 I think).

Anyway the problem is this :

The West steps go to a distance of about 25 in 13 or so steps, before reversing direction and doing the East Steps. Backlash is then cleared, and the West steps to a distance of 25 in 13 steps. Now, when it reverses, the South steps, make very little change to distance. So on the screen I will actually see something like ....

South Step 13 - Dist 25

South Step 12 - Dist 25

South Step 11 - Dist 25

South Step 10 - Dist 24.7

As you can see is hardly budges in South !

I have tried ASCOM pulse guided and ST4. I have changed the cables, but the situation is still the same. Always an issue in South ....

I have attached an example PHD Calibration log. Does this log look correct  ? - The graph shows the clustering in the South direction for DEC.

Calibration doesn't actually fail and guiding does start. But I can't workout is this is correct behaviour or not, - or even if the logs match the screen output I am seeing. I have attached a log below the image.

Thanks

Alistair

Log of this graph is below :

 

PHD2_GuideLog_2016-11-30_222138.txt

 

[Thalestris24]

Hi

Normally I think that's caused by backlash, but with a belt mod you have to make sure the belt is tight and the mount is accurately balanced without being east heavy. Also, you can still have worm gear mesh problems (see Astrobaby's excellent guide)

Louise

ps your calibration looks ok to me

pps another thing might be the fast re-center setting

[geordie85]

On both my old eq5 and new Neq6 I have always had problems with south calibration but my guiding has always been spot on. My Neq6 always tries nudging in south aswell. just check your subs for star trails. if you get none then don't worry about it.

[msh1]

yep looks like mine as well ,see how the stars look are they round thats all that counts

[AlistairW]

Interesting - i never tried the proof of the pudding and took an image - lol - just assumed an issue. I shall make amends and take an image. Louise I did notice that fast recenter after calibration - that threw me initially too - as the steps would jump ( from 13 to 6 ) for example. 

I am wondering if the way this works is that most of the calibration is done in one direction anyway - so reversing the calibration is not gaining a lot more - hense the step jumps.

Thanks

Alistair 

 

 

 

 

[kirkster501]

12 hours ago, geordie85 said:

On both my old eq5 and new Neq6 I have always had problems with south calibration but my guiding has always been spot on. My Neq6 always tries nudging in south aswell. just check your subs for star trails. if you get none then don't worry about it.

^^^^This.  All that matters is that your subs have round stars.  Rest assured, without guiding you'd be throwing half your subs away.