What constitutes good guiding in PHD2

[beamer3.6m]

I think my guiding is very good in PHD2 with 10 minute subs no issue at all.

My question is when looking at the graph what numbers/results do I need to interpret to see how good my guiding accuracy actually is and what is a good number to achieve?

[Shelster1973]

I would not obsess on the graph....you will go mad if you do.

As you have said, teh end image of 10 min subs is working so take that as you have guiding nailed in PHD2...proof of pudding etc etc

[MattJenko]

The scale is all important. If you have plugged your guiding rig specs into PHD2, then you get a guide graph in arc secs which you can then translate into performance for your main imaging rig. Say you have a guide graph oscillating between +/- 2", then you are looking at a 4" wobble of the main image. You then look at your imaging specs to see the impact. In my setup, I use a reduced ED80 with an Atik 414ex, which gives me 2.6 arc secs/pixel, so a wobble of 4" would mean my stars are wobbling just under 2 pixels on average for each sub. This might well give me perfectly round stars if the wobble is uniformly random, but they would be spread out more than they could be and I would be losing potential resolution.

[MattJenko]

This is why as the focal length increases, good guiding becomes harder, as the arc secs/pixel ratio drops. A +/- 1" guide graph on my rig is excellent, but if I had a scope at 2000FL (like a native C8) with my Atik, I would be looking at 0.65"/pixel and a +/- 1" wobble would mean stars moving more than a pixel around the place in all my images.