[Beginner help] Strange PHD2 calibration warning

[choochoo_baloo]

Last night was my first attempt at PHD2 run guiding.

I've been careful to do as much preparation beforehand:

• make the piggybacked short refractors as rigid as possible with clamshell clamps, stainless socket head bolts, tidy cabling etc.
• Built the guide camera dark library.
• Slightly defocused the guide scope to avoid "saturation" warnings - I never had a star lost warning, and the SNR remained ~>15 throughout

My next step is to analyse the guide log file files to hopefully diagnose improvements e.g. I reckon my DEC balance is way off.

My first questions that I'd like help with are:

1. Why did I get this type of warning, seen below, after each new calibration having slewed to a new part of the sky?
2. How do I fix this issue?

Thanks in advance.

 

[almcl]

I am not an expert in PHD2, but the calibration looks OK from the screenshot.

You got the message because it was different from the previous one - guide camera at different angle is a possibity but could also be the parameters in the setup dialogue.  I think the cause in this case was the declination rate, why that's changed is something you may be able to work out (leaving the dec clutch loose is a favourite of mine).

If you are happy with the calibration, check the box 'Don't show calibration alerts of this type' and then click on 'Accept calibration'. 

[Pompey Monkey]

What declination are you calibrating at?

If it it's too far from the celestial equator then error sare more likely creep in.

[Stub Mandrel]

It may simply be because it's a significantly different part of the sky, but more likely it's a change in balance combined with a degree of backlash.

Once you have PHD working and chase  better results, you will probably want to 'tune' your mount and balance.

[michael8554]

You have a nice 90 degree Cal graph with very nearly  equal steps in both axis, despite the huge difference in ra and dec guide rates.

Are you letting PHD2 auto select the guide star? That star won't  be saturated.

The PHD2 guys don't recommend defocusing the guide star unless the stars are very tiny ones from short FL guidescopes, yours isn't.

Are you ST4 guiding, using the third ST4 socket on the guidecam?

In that case PHD2 won't know where the mount is pointing each time you Cal, so will report the difference if you Cal at a much different Dec.

If you are Pulse Guiding you should Cal at zero Dec and around the meridian, and then PHD2  will have the ra and dec readings from the scope and can compensate when you move in ra and dec to the target.

Guiding at 1sec exposure might be too fast, resulting in "chasing the seeing" (air turbulence).

Michael