Calibration question.

[Larry 1969]

Hello again!

You're probably getting tired of hearing from me so thank you all for your patience.

When I launch PHD2 and it does a calibration I get a message something like "calibration completed to too few moves. Accuracy could be affected".
I see in the user guide that it should take between 8 to 14 moves but mine completes in about 4 or 5. What setting do I need to change to get it to
make more moves? Maybe I should bin 2x2? Would that make any difference?

Thanks!

Larry

[JayTee]

What is your calibration step size and your mounts guide rate?

From PHD2 manual regarding calibration step size:

You can adjust the value depending on whether the guide star is moving too quickly or too slowly during calibration. As a general guideline, it is good to calibrate within about 30 degrees of the celestial equator (declination = 0), and to use a calibration step size that will result in 8-14 steps in each direction. The 'Advanced...' button to the right of this control will launch a dialog that can help you compute an appropriate value (see below)

Also, what recommendations does the GA make after a successful calibration?

JT

[dritter]

I agree that the calibration step size is probably the first place too look. Specifying smaller steps will result in more steps and that should clear up any warnings.

Failing that, another approach might be to slow down the guide rate in the mount. If you are guiding at 1X sidereal, then maybe slow it down to 0.75x or 0.5x. This will cause the mount to move less distance during the time specified in the calibration step size. The end result should be more steps to move the same distance. The guide rate is usually a mount parameter and it is set in the hand controller or in EQMOD if you're using that.

Having said that, if you are already at 0.5X guide rate or slower, probably best to just leave it alone and go with a smaller calibration step.

And also note that a slower guide rate usually means the mount will take longer to fully make a correction during normal use. This is not wholly bad though since it can help keep the mount from thrashing around (aka chasing the seeing) when the seeing conditions are less than optimal.

[JayTee]

The current wisdom from the writers of the PHD2 software is to run your mount as fast as it will go for your guide rate. I always run my mount at .99 sidereal. Using a slower guide rate for your mount just handicaps the software.

The best way to keep from chasing the "seeing" is to use a longer guide exposure, anywhere from 2 to 5 seconds based on how bad the seeing is.

Cheers,
JT

[UlteriorModem]

Yep, step size is too large.

[Larry 1969]

Thanks for the replies!
I'm brand new to guiding. I didn't run guiding assistant. The step size is whatever the default is. I never changed it.
I read on here under Guiding Tips to use .9X speed so I set that.

I have much to learn and few clear nights to do it...

I did have some success last night though! I'm just changing too many things at one time. New mini PC, new install of APT beta 3.85, new install of EQmod and just added PHD2. Getting all of the settings right took me most of the night but I did finally get it all working.

I will work on PHD2 next although I was guiding last night and it seemed to be working.

I was only able to get 4 X 180" on M51 before it got too high in the sky.

I switched to M13 and got 25 X 120" on it and I was growing tired at 3:00 AM. Shot some darks and bias frames and went to bed.
I'll shoot some flats (which is also new for me) today and see what I got.

I'm just super relieved that everything is working!

Thanks again!

Larry

[UlteriorModem]

I have much to learn and few clear nights to do it

Yep, welcome to the world of AP and good luck

[Larry 1969]

Thanks for all your help!
The default step size was 1000 so I figured if I want to double the steps I should reduce the size by 1/2 so I set it to 500 and it worked!
Calibration completes with no warning message! I must say the guiding graph looks terrible but it appears to be working well. Probably
because of my rough polar alignment.

Larry