Guiding with PHD2 on CPC 8 alt-az without equatorial wedge but with derotation (falcon rotator)

[VerBaL]

Hello everyone, I think I have read enough in the PHD2 documentation and on the OpenPHD guiding groups but I can't find the issue in my case. Indeed, I noticed when using the manual commands in PHD2 that the telescope does not move as requested.

Clicking on North or South, my telescope points only downwards, and clicking on East or West, the telescope only moves towards the west... So it's impossible to complete the guiding assistant. I would like to point out that I have tested 2 different straight ST4 cables (the one provided with my Player-one Ceres-C and another one bought new) but the results are exactly the same.

The guide scope has a focal length of 180mm and the pixels of my guiding camera are 3.75 micrometers. Here are the screenshots of the settings made in PHD2:

I also verified the telescope's behavior via the display of RA/Dec coordinates visible in a submenu of the telescope's control handset. Here are the photos of the results after clicking on each of the manual PHD commands. We notice the same thing. There are only two possible movements out of 4:

1 Initial State:

2 After clicking on East (1000ms):

3 After clicking on Ouest (1000ms):

4 After clicking on North(1000ms):

5 After clicking on South(1000ms):

If anyone has already had this type of problem, I am interested in a solution !!! Thanks in advance

Sincerely
Charles

[Brian Valente]

Hi Charles

See this thread:

https://groups.google.com/g/open-phd-guiding/c/FKf3tyh37xg/m/dH_lB5tgAQAJ

In particular, Bruce's comment here (the mount in the thread above is a PW l-series, but same applies to your situation)

PHD2 doesn't explicitly support alt-az guiding so it doesn't try to convert RA or Dec commands into Azimuth/Altitude adjustments.  That can't even be done using the pulse-guide command because the ASCOM standard specifies that pulse guide directions are east, west, north, or south.  PHD2's responsibility is to transform from the camera sensor coordinate system into the east-west-north-south coordinate system.  That happens during PHD2 calibration.  I don't have any way to know what the PW driver or mount firmware do when handling pulse-guide commands when the mount is in alt-az mode and whether the behavior changes in the presence of a rotator.

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Brian Valente

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[Bruce Waddington]

You might also want to take a look at these links.  I can't vouch for their accuracy but they seem credible to me.

https://www.cloudynights.com/topic/697479-guiding-alt-az-mounts-with-phd2/

https://telescopemount.org/guiding-the-panther-alt-az-mount-with-phd2/

https://telescopemount.org/short-exposure-alt-az-astrophotography-learn-how-to-get-great-results/

In the future, if you need help please follow the instructions in the 'Getting Help' discussion rather than posting a bunch of screen-shots.

https://openphdguiding.org/getting-help/

Cheers,

Bruce

[Mike Gilchrist]

Charles-  I too have a 8" CPC, and I am a novice.  I have yet to get a good calibration or successful guide.  But, I have seen that the best way to connect to a celestron scope is through their CPWI software.  First, open the CPWI program, then open PHD2.  When connecting to equipment in PHD2, enter your camera, and in the "Mount" box, use "CPWI (ASCOM)".  There should be no connection between the camera and the mount.  Just the camera to the PC, and the hand control to the PC.  And obviously, the hand control is connected to the mount.  Further, I don't believe the  "Manual Guiding" control in PHD2 works unless the software is actively guiding on a star.  I hope this helps.   

[mj.w...@gmail.com]

Hi Charles

You have the mount on a wedge, and have switched the mount setting to Polar/Equatorial  Mode ?

 So PHD2 should be happy guiding.

Unfortunately the ST4 Protocol is far from being a standard.

Here's how some makers think the wring should be:

You should find out the pin connections for the mount and for the camera and wire accordingly.

As Mike G suggested, ASCOM Pulse driving is a better solution ,and does away with this ST4 confusion.

Michael

Wiltshire UK