PHD Guiding will not calculate

[Dennis G]

Having difficulty getting the PHD Guiding program to calculate.
details. LX90 8 inch scope. modified Meade finder scope as the guide scope. DMK21AU04 as guide camera. USB RS232 to 505 connected to HBX.with all the recommended drivers.
order of set up. check the Com Port number. set the camera. connect the camera. focus the star. stop. box the star. press PHD target. Box turns green, crosshairs orange. box remains locked to the star but moves away from the cross hairs to the right very very slowly and a wee bit down. no calculations no green cross hairs, not guiding .
Appreciate help for success.
Dennis G.

[mill (Martin)]

Dennis you have to let it go and do it's thing.
It is calibrating.
After going to the right it will go to the left and then up/down.
When finished the lines will turn green and guiding begins.

Martin.

[bmitchell82 (Brendan)]

you are using the finder guider im assuming and in which means your star will take a long time to calibrate the required 25 steps (thats what it was last time i used it). bump up your calibration step size remembering I think its in milli seconds 1000 milli seconds = 1 second. Also if i remember correctly my calibration for the finder guider used to take me 3-5 minutes and hence why i cracked it and moved to maxim but thats a whole new ball game!

[Peter.M]

If your trying to guide your lx90 with a finder I would suspect that the results will not be great anyway. At 2000mm focal legnth the imaging camera is going to see far more movement than the guide scope can detect.

[mithrandir (Andrew)]

You'll need to increase the step size in the "brain" to get PHD to calibrate in a reasonable amount of time. The secret is to pick a size that takes about 12-15 step in each direction. For your finder you'll probably need something of the order of 1500 to 2000.

At the bottom of the PHD screen it shows how far it wants the target to move and how far it has moved since calibration started. My rig (500mm guide scope, Atik 16ic as guide camera) wants the target to move 25 pixels, so if the change isn't around 2 pixels each step I know the step size is not big enough. If it was more than say 2.5 the size would be too big.

Be aware it is ***much*** harder to calibrate on targets near the celestial pole than on those near the celestial equator.

Brian, if you were using 1000 it probably wasn't enough.
Peter, PHD does sub-pixel guiding so it will work better than you expect, but I'd agree a longer guide scope would be an improvement.

[Dennis G]

Originally Posted by mill

Dennis you have to let it go and do it's thing.
It is calibrating.
After going to the right it will go to the left and then up/down.
When finished the lines will turn green and guiding begins.

Martin.

Thanks Martin for your reply it provides encouragement to continue and may I assume then that all is working? Just one question. The box moved sufficiently to be parted from the cross hairs. Is this stil OK?
Reading Peter and Brenden's reply I assume I must increase the exposure or what? a little more info would be helpful and thanks to all who gave their time to reply.
Dennis G

[Dennis G]

Originally Posted by mithrandir

You'll need to increase the step size in the "brain" to get PHD to calibrate in a reasonable amount of time. The secret is to pick a size that takes about 12-15 step in each direction. For your finder you'll probably need something of the order of 1500 to 2000.

At the bottom of the PHD screen it shows how far it wants the target to move and how far it has moved since calibration started. My rig (500mm guide scope, Atik 16ic as guide camera) wants the target to move 25 pixels, so if the change isn't around 2 pixels each step I know the step size is not big enough. If it was more than say 2.5 the size would be too big.

Be aware it is ***much*** harder to calibrate on targets near the celestial pole than on those near the celestial equator.

Brian, if you were using 1000 it probably wasn't enough.
Peter, PHD does sub-pixel guiding so it will work better than you expect, but I'd agree a longer guide scope would be an improvement.

Andrew I missed reading your reply. I will check it all out. and many thanks for your help.
Dennis G

[mill (Martin)]

Dennis you have to increase the calibration time to about 2000 ms because if you use a finder guider it won't move much.
Once the box is moved outside the line it will starting to move back untill it will be in the center again and then it will move another direction and then back to the center again, guiding will begin at that moment.