PHD help needed

jjjnettie (Jeanette) · #1 19-11-2009, 08:46 PM

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 (Chris Malikoff) · #2 19-11-2009, 09:00 PM

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 (Marc) · #3 19-11-2009, 09:03 PM

Quote:

Originally Posted by 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?

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 (Marc) · #4 19-11-2009, 09:04 PM

Quote:

Originally Posted by 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.

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

jjjnettie (Jeanette) · #5 19-11-2009, 09:09 PM

It's never simple and straight forward is it.

Omaroo (Chris Malikoff) · #6 19-11-2009, 09:09 PM

Quote:

Originally Posted by multiweb

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

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:

Quote:

G/S (Guide Setting)

This function allows you to select the speed at which the motor moves when corrections are made via the hand controller. Once the drive is activated, the default setting is .3 times sidereal rate. Press the button to change the guiding rate. The sections are .3x, .5x, 2x, 4x, 8x, and 16x sidereal rate.

For guiding, use either the .3x or .5x setting. These two rates allow optical use with auto guiders. For auto guiders, use 2x-4x setting for calibrating and .5x for playback. The faster settings of 2x, 4x, 8x, and 16x are perfect for positioning objects within the field of view.

jjjnettie (Jeanette) · #7 19-11-2009, 09:10 PM

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

multiweb (Marc) · #8 19-11-2009, 09:13 PM

Quote:

Originally Posted by Omaroo

No Marc - that's wrong. Even Losmandy mentions this on the Yahoo forums. With the SSAG this is the recommended method.

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 (Jeanette) · #9 19-11-2009, 09:15 PM

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

multiweb (Marc) · #10 19-11-2009, 09:16 PM

Quote:

Originally Posted by jjjnettie

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

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 (Marc) · #11 19-11-2009, 09:16 PM

Quote:

Originally Posted by jjjnettie

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

Nah... very unlikely.

Omaroo (Chris Malikoff) · #12 19-11-2009, 09:18 PM

Quote:

Originally Posted by multiweb

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?

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 (Jeanette) · #13 19-11-2009, 09:19 PM

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 (Marc) · #14 19-11-2009, 09:19 PM

Quote:

Originally Posted by 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:

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.

Omaroo (Chris Malikoff) · #15 19-11-2009, 09:20 PM

Quote:

Originally Posted by jjjnettie

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

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 (Chris Malikoff) · #16 19-11-2009, 09:23 PM

Quote:

Originally Posted by multiweb

oh... is this specific to the digital drive?

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 (Marc) · #17 19-11-2009, 09:23 PM

Quote:

Originally Posted by 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.

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 (Chris Malikoff) · #18 19-11-2009, 09:30 PM

Quote:

Originally Posted by 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.

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?

From Stark Labs site:

Quote:

In PHD Guiding, all calibration is taken care of automatically. You do not need to tell it anything about the orientation of your camera, nor do you need to tell it anything about the image scale. The automatic calibration routine takes care of this for you. Odds are you won't ever need to set a single parameter. Just select your star and hit "PHD Guide" and let the software take care of it.

Omaroo (Chris Malikoff) · #19 19-11-2009, 09:33 PM

You confused yet Jeanette?

multiweb (Marc) · #20 19-11-2009, 09:35 PM

Quote:

Originally Posted by 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?

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.