Re: PHD2 Guiding issue on AP1100

Roland Christen

Expand the ASCOM driver window and you will see more functions including the com errors. I doubt that you are getting any. Use the ASCOM driver to move the mount in RA. If you can do this, the mount is ok and the problem is elsewhere.


-----Original Message-----
From: Bruce Donzanti <donza2735@...>
To: main <>
Sent: Sat, Dec 7, 2019 11:54 am
Subject: Re: [ap-gto] PHD2 Guiding issue on AP1100

Also, can you tell me where I would find the communication error display in the AP ASCOM driver window?  I was told that a  window will display the number of transmit and receive errors it gets on the mount connection.

On Sat, Dec 7, 2019 at 12:30 PM uncarollo2 <chris1011@...> via Groups.Io <> wrote:
If you have a CP4 you have 4 input choices for sending guide data (1 USB, 2 serial and the guider port). It may be that the one you are using has a fault. You can try one of the other inputs. If you have a planetarium program attached to one of the inputs, you can try sending a move command, slew or centering, to verify that the mount is moving. This will tell you whether the mount controller is functioning and that the input you are using for guiding may be faulty.


-----Original Message-----
From: Bruce Donzanti <donza2735@...>
To: main <>
Sent: Fri, Dec 6, 2019 9:14 pm
Subject: Re: [ap-gto] PHD2 Guiding issue on AP1100

Thanks but my guiding has been fine for months.  I should have stated I am in a permanent pier observatory so I do not keep re-calibrating.  Also, I did try to create a new profile but since RA will not respond, it will not create a new calibration curve.  So, I am stuck. 

On Fri, Dec 6, 2019 at 10:06 PM OlivDeso via Groups.Io <> wrote:

I never faced any guiding issue with the AP1100 so far since years (I have the serial #10) and GTO CP3

But as far as I understand, it is very unlikely that the issue comes from an defective USB cable nor the RS232 cable if everything works well except the AD guiding.

I would rather suspect a PHD or AP Ascom driver wrong setting.

How is PHD calibration ?  -> calibrate once on the ecuador close to the meridian at the begening of your observing session and then slew to the target.

Of course if you have a fixed setup and don't remove your guiding camera, you only have to calibrate PHD once forever.

So first of all review PHD calibration data. A good calibration is really a keep point to get a good guiding.

The verify the AD agressivity and the AD MnMo :

AD agressivity should be higher or equal 50%. 70% is a good starting value for average conditions.

MnMo in the threshold under which PHD will not correct the guiding error : It should be set to a value corresponding to about half of the main camera pixel size. 
But the unit value is pixels of the guide cam, so you have to do so basic maths to calculate it from the main cam pixel sampling.

For instance if your main cam has a sampling of 1" per pixel and you guide cam a sampling of 3". You would like to set the MnMo to 0,5".
So 0.5" is equal to 1/6 of the guide cam sampling -> so you would set the AD MnMo to 1/6 = 0.17

Concerning the DEC, I use to set the MnMo to the double of AD MnMo and agressivity to about 30% -> this is to avoid guiding in 2 directions in DEC which is the second keypoint to get a good guiding.

In the AP driver, verify the guiding speed and maybe the PEM state. try disabling the PEM if enabled.

Example of what I am curently geting right now form a remote EQ8 in Chile (I am in France) : the EQ8 is not as good as the AP1100 in AD tracking (from far) but the tuning principle remains the same.
Look at the graph : you can see that the DEC stays at one side of the axis and then on the target you can also see that the hits are located only at te uper half and well grouped in DEC at least.
The main limit of this EQ8 is the AD

(the star is a little bit saturated and has a triangle shape, but the guiding is good enough for the moment....until we replace the EQ8 by an AP one day)

Image en ligne


Le samedi 7 décembre 2019 à 03:30:52 UTC+1, Bruce Donzanti <donza2735@...> a écrit :

I have been guiding just fine on my AP1100 mount for a few months but the other night RA stopped responding.  I have been chatting with the folks on the PHD forum and they looked at my logs.  They are suspecting a bad USB cable.  I changed the cables on both the guide and image cameras which connect to a powered USB hub on top of my scope which then runs down the pier to my laptop.   I also changed that USB cable as well.  I then cleaned the RS232 cable from the CP4 box which also runs to my laptop.  To see if this was an issue, I removed it and tried the autoguider cable instead.  Anyway, I continue to have the same issue.  So, just asking if you have ever heard of this problem and if I am missing something else to try.


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