How long does it take for PHD to calibrate for you?

[White Rabbit]

Hi Guys.

I'm delving into the world of guiding (Joy).
I've set it up before and got it working using PHD/Eqmod a microsoft web cam taped to my 32mm eye piecethough my 8" newt, dont laugh.... hey, I said dont laugh it worked just fine.

Last night i thought I'd try and tape the web cam to the finder scope, (hey I said dont laugh) and see if I could get it to guide.

After much futsing around with the calibration in the brain I settled on about 8500, default is 750 he he he. It would calibrate but man it would take about 15 minutes. The more I increased the calibration the longer it would take. I assume this is because the magnification is smaller and therefore the movement is smaller.

So my question is how long does it take you to calibrate phd on a star?

thanks

[dugnsuz]

Haven't timed it, but at a guess about 60 secs to do RA and Dec.
Doug

[leon]

As Doug mentioned unless it, the scope is pointed pretty close to the SCP, it can take a little longer, but usually about a minute or even less.
15 minutes is just to long.

Leon

[gbeal]

It will also depend on the exposure time. On bright stars I sometimes use .5 second, and when this is going I can be done in way less than the minute my two colleagues suggest.

[AlexN]

Indeed.. it depends of a few things.. as gbeal, leon and doug mentioned..

In my experience, anywhere between 30 seconds and 90 seconds is normal depending on exposure time, calibration rate, guider focal length etc etc..

[dugnsuz]

Timed it!! 70 seconds dead!
Doug

[mick pinner]

l assume it could also depend on the processing speed of the laptop/computer?

[g__day]

Depends on the step size - I beleve a smaller step size, with longer exposures would give you the best guiding. However I often use 2.5 - 3 second exposures with 300 msec steps - which might take a few minutes (less than 5). The longest I ever tried was 5 sec exposures on 150 mssc steps - no guide easily found in the frame around the Helix nebulae - wasn't much of a success.

[celstark]

8500 ms is WAY TOO LONG!

Remember, what PHD is doing is taking a picture, moving the mount, taking a picture, moving the mount, etc. Each motion is "calibration step size" long. So, you're moving the mount at guide speed for 8.5 seconds each time.

I'm going to suggest something here that I've suggested to a number of users. PHD isn't actually moving your mount and you're not actually calibrating. Drift and/or PE are faking a calibration (PHD doesn't know if it moved the star or if something else did -- it's smart, not psychic). Use the Manual Guide dialog to make sure your signals are really getting through to the mount (I can hear my motors change pitch for example). On my 250 mm f/l guide scope I run a second or two for the cal step size and that's probably as long as you should ever need to go on it.

Craig
PS - I'm the author of PHD.

[mill]

I normally get PHD do calibration in 14-15 steps in each direction.
This means that if i am calibrating near the pole i just set the calibration steps longer (eg 1700ms instead of 750ms).
You dont want PHD to go for 35 steps because i found out that it will not guide better or worse than with say 15 steps.
The way to make the guiding better is to set the sliders on the RA/DEC so the graph line doesnt oscillate up and down.
This is all with a DSI pro on a 600mm f/l guide scope.
So it all depends on f/l and guide camera and position in the sky.
As soon as you have to use more than 2 seconds there must be something wrong.

[h0ughy]

well there you go -and all this time i thought it was done with smoke and mirrors:D;) . Thanks Craig for the detailed explaination:thumbsup: . I have found it not to take no longer than a minute or so, then it was off happily guiding away.

On a side note - do you browse IIS much:)

[White Rabbit]

Hi Guys.

I fixed my problem, allthough not all my guiding problems. I can calibrate in about 25 steps now, but guiding is still off. If the weather ever clears up I'll be able to refine what I'm doing....I hope.

Here is what I did for anyone else that suffers the problem.

In EQmod, hit the display window until the "Pulse Guide Monitor" is displayed. If you increase the pulse width PHD calibrates much faster. Although I'm sure If I'm just moving a fundimental problem with my set up around.



Thanks

Sandy

[Geoff45]

Sliders? Which sliders are these?

[keppar]

All
On the subject, my calibrations do take about forty steps.
This dosent bother me too much but now I have a problem that every time it goes to guiding I get the flashing red signal saying Low SNR. It want even guide for more than a couple of seconds. Star seems bright enough and calibration even though a little long ,there's no problem.What am I doing wrong?
Thanks if anyone can give me help Kepp

[TrevorW]

In all honesty I can only think that your Polar alignment is out or you've got a dicky mount.

On the other hand how long have you set the PHD exposures.

Calibration now for me usually takes about 20-25 steps

I've only ever had a couple of problems using PHD and they have resulted from either picking the wrong type of star to guide on, leaving the mount unattended or my polar alignment was out

[keppar]

Thanks
Is polar alignment important, My mount is "roughly" polar aligned and my mount is working fine. It was guiding ok for a while, this problem has just started. Cannot guide at all. Keep getting Low SNR

[mill]

Hi Geoff.
Pictures say more than words :)
First pic is where to press the button to get to the RA and DEC fine adjustments, these settings have to be set back to 100% everytime you do a new calibration, or else the pulse guiding makes the calibration steps the percentage you have the sliders on. :eyepop:

Second pic is the sliders you have to move to smooth the guiding out.
Experimentation is to be done here.

Third pic is what you get when you press the settings button.
Always put the pulseguide sliders on 0.90 here when calibrating or else calibrating will take very long as with the RA and DEC sliders not on 100%.

[celstark]

Kepp,

Can you take a screencap or do a File, Save and dump the raw sensor data to a file? Remember -- too bright is as bad as too dim. Big fat guide stars are poor choices (as they've likely saturated the CCD)

Craig

[keppar]

Ill try craig.
Also I cant seem to be able to change the sliders on shot 3 Where is the settings button
thanks Kepp

[keppar]

One more question When calibrating and PHD you do have sidereal running?

[h0ughy]

yes

[keppar]

Martin How do you change the sliders on EQMOD it wont let me Where is the settings button?
Kepp

[keppar]

Craig
Here are a few screen shots of my attempts at guiding last night. Camera is a QHY5 using a EQ6 which has been just replaced with a new one as old one was sent back because of same guiding problem. All leads have been replaced.Calibration seems to be alright but as soon as guiding starts I get LOW SNR I have tried numerous times changing parameters within PHD only to get same result. You will notice that Dec does not want too begin guiding and RA starts off quite a drift When I first started guiding (6 months ago) there was no issue,this problem has just started, to a point where I cannot guide at all. I believe the stars I am using are neither too bright nor too dull. Any thought Camera maybe ???
Thanks Kepp

[keppar]

Sorry try these

[keppar]

Craig here is a log file from that night

[White Rabbit]

How do you make a graph using Xcell with the log file? I've had a stab at it but cant figure it out. Does anyong know how to do it?

Thanks

[leon]

I just can't get a grip on this, and why PHD is such a pain for you guys.

I actually do nothing more than find a moderate Star, set it a 1.5 always, regardless of conditions, and walk away, it has never to this day failed me, unless of coarse the clouds roll in. :shrug:

leon :thumbsup:

[TrevorW]

I don't use PHD with the associated Ascom platform just inatall the PHD drivers connect up and away it goes

By the way Keppar are these actual screen shots while tracking because if they are then the reason you are getting Low SNR is because you are capturing an image at 2/10 and 5/10 of a second per exposure.

Trevor

[keppar]

Trevor
Yes this is tracking. I have got it going ok now by changing the settings in the "brain" to -Min motion set at .05 . Still using .5 sec exposure with no problems, did try 1.5 -2 sec exposure when I was having problems that did not fix it
Kepp

[mill]

Kepp, just click the boxes above the sliders so they have a "v" in them.

[pjphilli]

Hi Leon
I'm with you - PHD works like a dream for me and I have never had any problems once I set up my QHY5 imager to get decent guide stars.
To answer the original question, I usually try 1 second images for a start and I find that PHD goes about 12 steps E then 12 steps W then about 2 steps to get over the DEC backlash then 6 steps N and a few S before it decides to get into the guide mode. Less than one minute in all. I am using a QHY5 guider on a Mak100 at f6 and usually 1 or 2 second guide images. I polar align accurately and set PHD for Auto DEC guiding. My guiding is usually under +/- one pixel. It infrequently strikes a period when it goes up to say 3 pixels in RA for say 6 guide pulses then settles back down. All other things being equal I think this is when it may strike a rough patch on my HEQ5Pro mount gears? Any comment Leon?
Cheers Peter