PHD settings for a short refractor?

[photosinferno (John)]

Hi ppl
I've got a william optics 72 megrez running on an HEQ-5 mount, me and another IIS member was trying to get PHD 'guiding' last night and it just wouldn't dec/ra struggling. Have a basic polar alignment and the system is balanced -thanks to another IIS member for getting me this far!
So my question is does anybody have a starting set of 'numbers/settings for PHD with a similar set up?
Just throwing this out there and hoping someone might throw an answer back

Many thanks
John

[pluto (Hugh)]

The numbers are going to depend on your guide camera (sensor size, pixel size) and focal length of your guide scope, or if you're using an OAG.

In my experience you need a very good polar alignment and good balance otherwise PHD will be all over the place.

You can use PHD to drift align though which makes it a fair bit easier, I use the technique described here:
http://njstargazer.org/PolarAlignment.asp

[Merlin66 (Ken)]

http://openphdguiding.org/

Have a look at PHD2 - it has a pretty good calibration procedure.

[photosinferno (John)]

Pluto/merlin,
Thank you for your replies.

Pluto - I'm guiding with an Orion SSAG -and the Orion 50mm -162mm focal length guider.

Merlin, yes I had thought of downloading PHD2 so you 'tipped' me over the edge and I did so today.

My findings thus evening are that PHD2 allows you to set the focal length of your guide scope - so for the first time in a long time PHD seemed to be 'driving' the mount, however the guiding was off by miles.
Polar lignment was 4degrees out -but still the mount should gave guided for longer than 5secs I feel!.

Ho hum...test test test....

John

[MrB (Simon)]

In my opinion 4 degrees is far too much error. Guiding is not a cure for poor PA.
It should be relatively quick and easy to get the PA much closer than that.

[mithrandir (Andrew)]

The numbers PHD2 estimates need the declination of the target. The closer to the pole the longer the maximum guide pulses need to be. If you are using pulse guiding it can get the info from the mount. With an ST4 connection you have to tell PHD2 - at least until they add mount communication alongside "On Camera".

With an SSAG on a 400mm guide scope I set max calibration step around 1500. With your shorter guide scope you might need to make it bigger. You want calibration to take around 12-15 steps in each direction.

You should use PHD2's drift align to improve the mount alignment. If it loses the guide star that fast you are way off.

[pluto (Hugh)]

Originally Posted by MrB

Guiding is not a cure for poor PA.

Amen to that!