ST4 mount and aux mount?

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Alf Jacob Nilsen

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Oct 7, 2021, 11:16:33 AM10/7/21
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Hi guys,
I have the new AstroTrac360 (non ASCOM) mount installed.  The mount has to be connected to PHD2 via ST4-cable and guide camera.  According to PHD2 manual, you should select "On Camera" for mount set up and so select an ASCOM driver (e.g. AstroPhysics GOTO V2 Mount) as the "AUX mount".   I use WIN 10 from my PC laptop.

I can connect without problems to "On Camera", but when I try to connect the AUX-mount, obviously PHD2 cannot fint the mount as it is not there so an error message is displayed. 

Obviously I am doing something wrong. I have treid various ASCOM-drivers for the "AUX mount" (Celestron, iOptron, Meade), but same thing. 

Should the "aux" connection be left unconnected? Any suggestion would be greatly appreciated...

Thanks :)
best
Alf J.

Brian Valente

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Oct 7, 2021, 12:57:00 PM10/7/21
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Hi Alf

what guide camera are you using?

I haven't done this type of connection in a while, but usually it's guide camera connected to PHD2 via ascom, and then the mount connects to the ST-4 port on the camera and you choose "on camera" for mount type. In other words, PHD is communicating to your mount via the camera

aux mount is for ascom-compatible mounts. if you hover your mouse over AUX it will give you a pop-up explanation

Brian



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Brian Valente

Alf Jacob Nilsen

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Oct 7, 2021, 1:06:45 PM10/7/21
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Hi Brian….

I am using ASI178 for guiding. The mount is a non-ASCOM mount (https://www.astrotrac.com/) and the camera connects to the mount directly by the ST4-cable. The camera also connects to the laptop via USA. No problem here. For non-ASCOM mounts the mount selection in PHD2 should be “On Camera”, but the manual says that one should also select an AUX-mount connection, here is the text:

 

The "Guide-port" interfaces use a specialized, hardware-level control port available on most mounts.  To use this type of interface, there must be another device in the link between PHD2 and the mount:

  1. Any of the guide cameras which have an ST-4 compatible "on-camera" guider interface. Use the 'on camera' mount choice for these setups.
  2. Any of the Shoestring GP-xxx devices
  3. A supported AO device with a guide port interface

With this style of interface,  PHD2 guide commands like "Move west 500 mSec" are translated by the intermediate device (camera, Shoestring box, AO) into electrical signals necessary to drive the mount motor for the correct length of time.  

Aux Mount Selection

If you have selected an ST-4 style of guiding in the 'mount' section, that interface cannot be used to query the pointing position of the telescope.  As a consequence,  guider calibration won't be automatically adjusted for declination, nor will it be automatically flipped when the side-of-pier changes.  You can restore these features by specifying an "aux" mount connection that will be used to get the telescope pointing information.  An example is shown below:

Graphical user interface, text, application

Description automatically generated

For Windows users, the "aux" mount can use any of the ASCOM-compatible mount drivers, while Linux users can take advantage of INDI drivers.  The "aux" mount choice will be used only if the primary mount interface cannot return pointing information - it will otherwise be ignored.

 

 

The problem is that when I set this up, I cannot connect to the AUX-mount as there is no ASCOM mount present (obviously).  So I am wondering how to get around this problem or if the AUX should be left unconnected??

 

Best

Alf J.

 

 

Alf Jacob Nilsen
Reinferdalsveien 18
NO-4432 Hidrasund
NORWAY

ajni...@online.no
+4791384214


www.biophoto.net

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Brian Valente

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Oct 7, 2021, 1:10:12 PM10/7/21
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Alf

Read that section again - it says you can use AUX if you have an ascom-compatible mount. you don't, right?

the use of AUX here is really an enhancement that allows you to get pointing information so you can reuse calibrations. 

In your case, you will need to guide via ST-4 with on camera, and no aux mount. This means you should recalibrate guiding for each target, particularly when you change side of pier

Alf Jacob Nilsen

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Oct 7, 2021, 1:37:00 PM10/7/21
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Hi Brian….
Ok, thanks!  I’ll test this out as soon as it clears up and select “none” for the AUX-mount…. and I shall have to recalibrate guiding often, but that is OK and unavoidable with my set up….

Thanks again!

AJ

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