PHD help needed

[jjjnettie]

Ok, so I've done a drift align, and everything looks good.
Now Phd is saying it can't callibrate because my star isn't moving enough.
What the???
I thought that was the idea of drift aligning?
Any ideas what the problem may be?

[Omaroo]

I take it that you've finished drift aligning by this stage Jeanette. What guide rate do you have temporarily set whilst the actual calibration phase is taking place? I set mine to 4x while the process is going on, and as soon as calibration has concluded I set the rate back to 0.3x (default on my mount) when guiding starts. Unless you up the guide rate during calibration it will complain the way it has for you.

[multiweb]

Hi JJJ, that's got nothing to do with your alignment. If you've drift aligned you're good to go. Depending where your guide star is you might have to bump up the calibration steps. So click on the brain and set your calibration time to 2000ms to start with. See if your star moves. If it goes too fast reduce it, if it still doesn't move enough increase it. Don't have to change your guide rate on the mount. The lower the smoother your guiding.

[multiweb]

Chris you have to keep the same guide rate as the one you used for calibration.

[jjjnettie]

It's never simple and straight forward is it.

[Omaroo]

Plenty of mentions about this on the Yahoo forums Marc - so I'll disagree with you! LOL! With the SSAG this is the recommended method as far as I've read. As far as I know, calibration has nothing to do with velocity, but rather direction. PHD is discovering what angle the camera is set to so that it can compensate if not square.

From the Losmandy site:

[jjjnettie]

No go guys.
Maybe my drift align wasn't good enough.

[multiweb]

:shrug: First I have heard of... hang on a sec, we're talking about the guide rate x0.2 sidereal to x0.8 sidereal on the mount right? I don't understand why it has to be changed when you're actually guiding. The point of calibrating is PHD sending pulses to the mount and checking how far the mount moves right? If you then decrease the guide rate wouldn't the mount move less for the same pulse length?

[jjjnettie]

If my guide cam isn't square, could that cause this problem?

[multiweb]

If your drift align was wrong your star would move fast without guiding. Is PHD actually moving the mount? Have you tried to bump it manually? Everything's connected ok?

[multiweb]

Nah... very unlikely.

[Omaroo]

I thought the point of the exercise was to see where it moves... i.e. to be able to compensate for the camera not being mounted perfectly square to RA and Dec axes.

[jjjnettie]

Yes, PHD was talking to the mount.
I'll go back to the beginning.
Check my alignment. I'm notoriously lazy with this aspect. Phd doesn't like trying to catch up with my stars.

[multiweb]

oh... is this specific to the digital drive? With the Gemini I have two modes. Visual Mode and Photo Mode. I guide in Photo mode. But I don't change the guide rate. Mine is set to x0.5 and doesn't revert to x0.3 when guiding. Not that I know of anyway. :question:

[Omaroo]

That's the whole selling point of PHD - you don't need to square the camera to better than 15 degrees or so. Of course, you can "eye-ball" to better than a couple of degrees without really trying. The calibration process finds just how much out of square you are and then compensates for this in software.

[Omaroo]

Yes, I think it is if I remember. The reason I mentioned it to Jeanette is that it's something that she can actually try on her hand controller. The principles are the same - just to see it it works. I know that if I don't temporarily up the rate during that phase I get the same error as Jeanette - with everything set to defaults in PHD anyway.

[multiweb]

I think PHD doesn't care about the orientation of the camera. I remember Craig Stark saying that in one of his posts a while ago. That's the best thing about it. It doesn't care where North, south East or West is in the camera FOV. I'm pretty sure though that calibration is to know how far the mount moves for a known pulse time. pemPRO calibration works exactly the same way. The program needs to know how far the mount is going to move so then it can scale the pulses for known deviations while guiding. That's my understanding of it anyway.

[Omaroo]

I read that too, and from it read that the PHD user doesn't have to care, as such (which is the best thing about PHD) - but PHD certainly does. How else is the software going to issue an instruction to the mount to move in +/-RA or +/-Dec in reaction to star centroid movement if it doesn't know exactly where the axes are on camera? :shrug:

From Stark Labs site:

[Omaroo]

You confused yet Jeanette? :lol::lol::lol:

[multiweb]

Yeah you're right he does recommend to square the camera to the scope, so in increment of 90 is ok. NSE or W doesn't matter. I remember guiding once with a big offset like 30 degrees. I think it calibrated ok but I can't remember the guiding . Will have to try again. ;)

Re:guiding rate I checked your post again and it looks like the stepper vs. servo might work differently so may be the guiding rates available are diferent and the way to do it is different too for the digital version. Makes sense now. :)

[multiweb]

Yeah sorry Jeanette. We're probably confusing the hell out it now. It was Chris fault though, he started it! :lol: ... or did I? :P

[Omaroo]

Yep - that's cool. I've just been reading and it looks like the guide rate is upped on the Digital Drive (and other GEM mounts/controllers) with PHD so that the movement during calibration is exacerbated - in order for the camera to be able to clearly show the software how it's oriented by analysing large movements. Otherwise, it'd take several minutes longer to calibrate.

[Omaroo]

It was an evil ...plot.. :whistle:

[jjjnettie]

Damn computer crashed.
start again.
might work better this time??
Guiding is a good as I'm going to get it in the mood I'm in.
Good enough.

[multiweb]

One thing I've noticed with PHD, if it starts doing stupid things. Shut it down. You don't have to reboot your PC, but disconnect the USB on the guider, then replug the camera. Restart PHD and voila! It should start working fine again. :thumbsup:

[jjjnettie]

It crashed when I disconnected the LPI.
But don't get me started on the lpi and k3.
I think a good stiff drink will be in order once I get this up and running.

[jjjnettie]

:D And we're guiding.
Thanks heaps guys.
I really appreciate it.
Now....any suggestions as to where to point my camera?:question:

[multiweb]

Very cool! :thumbsup: Orion should be up soon.

[jjjnettie]

He's just clearing the roof of my house now.
I'm thinking M45 for a couple of hours then hit the Flame nebula.

[jjjnettie]

And if I'm still up for it, I might even drag out the 8" and have a go at Mars.

[multiweb]

Now you're a tease. All I can see from Sydney tonight is the cloud nebula. Been stearing at it for over a week now... :P

[jjjnettie]

Damn clouds. They spoiled my evening last night.

[mithrandir]

Drift aligning can come later. First you need to convince PHD it knows what's going on.

Did you check in the brain settings that:
"Dec guide mode" is right? Auto is probably best unless your mount is spot on.
"Max dec duration" is big enough? 2000 is usually a good value.
"Calibration step" is right for your focal length. 2500 works well on my 500mm guide scope

The pulse length is the maximum PHD will use. If a smaller amount works, it will not use the maximum.

Once you get it to calibrate, fire up "Tools->Enable Graph" and see how well it is tracking. A small sawtooth is normal. A big one means your alignment is not as good as you though it was.

If the camera is square with the mount, you can drift align by turning off the Dec motor, turning PHD's grid on, selecting "loop for frame and focus" and watch where the stars go. It takes some practice (I'm not that good at it), but does work.



PHD wants to work out which in direction RA & Dec movement commands move the stars. It doesn't care what the orientation is. If moving the mount only in RA causes the stars to move at 45 deg, that's probably fine. Making it square to the mount just makes it easier for you to make sense of. After all, how would you make an off-axis guider work if you could not find a star without using some strange orientation?



If PHD won't shut down disconnect the guide USB and try again. If it still won't die, kill it from task manager.