PHD guiding trouble

[Sammyb]

Hello - I tried my first night of autoguiding on monday night and it worked really well. I was using the SPC900NC with the finderscope of my SW200P Newtonian.

I tried again last night and for some reason it just wouldn't accurately guide. It went through the calibration OK (although it took a while) and then said it was guiding OK. So I started imaging (300s subs) and found I was getting star trails.

I did notice the guide star was deviating a little from the cross hairs on PHD - is this usual?

Also something I noticed when it finished calibrating for the first time was an error flashed up about being "unable to calibrate in Dec" or something. Not quite sure what it was as I didn't have chance to read it as the message disappeared but the software said I was guiding OK.

I'm confident I wasn't guiding on a hot pixel!

Any help you can give me would be appreciated.

Thanks,

Sam

[Stephen]

Well as you state there, it sounds like the calibration failed.

Make sure PHD can move the mount in RA and DEC (bring up the manual guide window) and ensure the mount moves (motors whir) when you press all 4 direcitons.

Then check the cables and connectors

[jgs001]

Something else to check, if the calibration failed, what value do you have defined as the calibration step ? Click the brain. The default is too low for a 400mm ST80, let alone a finder scope. Increase the amount to say 2500 and try again.

[Sammyb]

OK thanks for the input. I'll try again. I'm sure I'm connected OK.

Somethings I've been mulling over are:

(a) I had to scout about a bit with the finderscope for a suitable guide star. Could the finder be sufficiently off axis or...

( I don't think I had sidereal tracking activated in EQMOD.

Could these be a factor?

[jgs001]

The first shouldn't be, but if the mount hasn't been told to track, then I'd also not expect you to hear any noise from the motors.