Switch to ASCOM guiding from ST4 port guiding?

In the 2.5.0.8 changes you make the statement “SGPro’s recovery mode will no longer attempt to recalibrate your auto-guider under any circumstance. This may not always be good for folks that guide using ST-4 and should be fairly substantial motivation to guide in PHD2 via an ASCOM Telescope connection”. You seem to be saying pretty clearly that ASCOM guiding is preferable. I’ve be using my ST4 port on my Mach1GTO to guide for the past 4 years or so, and since it always seems to work I’ve never given much thought to switching. What are the advantages of guiding through ASCOM rather than through the ST4 port? I should get this figured out since you are now warning us about guiding with the ST4 port in future versions.
…Keith

Hi Keith,

I can clarify that part… there is no need to change from using ST-4 if that is what you are happy with.

However, you should setup PHD2 to connect to the AP ASCOM driver as the Aux Mount. That will allow PHD2 to know which side of pier the mount is on and what the declination is so that recalibration is not necessary and so that PHD2 can adjust calibration under all circumstances regardless of what happens in SGP’s recovery mode.

Here is a summary of the three possible ways to setup PHD2 for your mount:

Mount = On-camera, Aux Mount = None

In your current configuration PHD2 sends guide signals to the camera and the camera relays the signals to the mount via the ST-4 cable. No pointing information is available and no declination compensation is possible – recalibration is needed for target changes.

Mount = On-camera, Aux Mount = ASCOM

In this configuration there is no change to how guide signals are sent to your mount versus your current configuration. Guide pulses are sent exactly the same way via the camera. But with the Aux Mount PHD2 will be reading the declination and side of pier information from the mount when guiding starts. Guiding will take declination and side of pier into account.

Mount = ASCOM, Aux Mount = None

In this configuration guide pulse signals are sent through ASCOM. The ST-4 cable between the camera and mount is not used at all and can be removed. PHD2 will also get pointing information (declination) from the ASCOM driver.

On more thing: you’ll need to calibrate just once after setting up the ASCOM connection (Mount or Aux Mount). Calibrate at a low declination (near dec 0) to get the most accurate calibration. Select the option “Auto restore calibration” on the Guiding tab in the brain; then no need to calibrate any more unless you rotate your guide camera.

Andy

Thanks for the very clear explanation Andy. I actually have been connecting to my mount as an Aux Mount since upgrading to the newer PHD2 development build, so I’d already stumbled into that one. I didn’t realize that was what Ken was talking about with regard to recalibration. I had no idea about Auto Restore Calibration though so that is a big help - I will do a good calibration near Dec 0 and set that option - that’s assuming that clear skies return within my lifetime.

Good to know I can keep running in the configuration I have now or I can ditch the ST-4 cable and run using a single ASCOM connection in the future. I assume that, other than losing a cable, there is no real difference between the last two options? Again, thanks for explaining this so clearly.
…Keith

Keith,
With my G11 I noticed an improvement in my guiding when I switched from an
ST-4 cable to ASCOM pulse guiding. I don’t know if that will be true for an
AP mount, but regardless having one less cable to manage and potentially
fail is a no-brainer to me. I would ditch the ST-4 cable.

It really depends on the mount controller. Some mounts, like AP CP2 controllers are reported to work better with ST4 and not so well with ASCOM. A modern controller like your CP3 will work great with ASCOM (speaking from experience), as does the Gemini2.

Besides the fewer-cables benefit Joel mentioned, another slight benefit of using ASCOM for guiding is that for most modern ASCOM driver /mount controller combinations (including AP CP3) the guide pulse timings are executed by the mount controller: phd2 says “guide north for 10 milliseconds” and the mount does so, precisely timing the 10 ms. With ST4, the PC has to do the timing: telling the camera “guide north signal on”, sleep 10 ms, then tell the camera “guide north off” (*). The Windows OS is notoriously bad at performing precise short duration delays. I only mention this as a full disclosure of the difference between ST4 and ASCOM. In practice the difference on guiding would probably be small and perhaps hard to actually measure, but again, it depends on the controller.

Another difference is with diagnosing guiding problems. When an ST4 cable fails, the indication is failed guiding, and you won’t necessarily know that the cable is at fault. With an ASCOM connection, the ASCOM driver will report guide command failures to phd2 and can often provide information about the source of the failure.

Andy

(*) there are exceptions to this too. Some guide cameras, like the Starfish guide camera, can do the timing of the ST4 pulses.

Andy is right about using Windows timers to do the timing, they are vulnerable to other activity on the PC. However using an ASCOM driver isn’t a guarantee that an on mount timer will be used. With the Celestron driver the older motor controller versions don’t have an on mount guide control so PC timing is used. Later mounts do have on mount timing.

The trick is to make sure that the PC is fairly powerful, isn’t busy and that not too much other telescope activity is going on at the same time. I try to prevent additional commands, such as reading position during a guide, being sent.

Chris

This is a really helpful discussion Andy, Chris and Joel. It’s no problem for me ditching the ST-4 cable - as you say Joel, it’s one less thing to worry about. My only concern with regard to my computer not being busy Chris (it’s a 1 year old Intel Core i7 with 8GB RAM so it is powerful enough I think) is that I use an ICRON Ranger link to my observatory through a single Cat5 cable so all traffic (guiding with a QHY5 & 60mm guidescope, mount control, 2 imaging cameras, focusers and FW) runs through the one cable. I suppose that’s as much a problem for the ST-4 as for the ASCOM mount controller? But given my setup, do you still recommend changing to ASCOM control of my CP3 Mach1GTO mount?
…Keith

@MicroAstro My apologies… re-reading my post, I did not mean to imply that you should ditch ST-4 guiding if it works for you. Usually the reasons people don’t use ASCOM based guiding via PHD2 are:

  • Mount supports only 1 connection and SGPro has it (in this case use the Telescope Hub driver)
  • ST-4 works better for you (use the aux ASCOM mount as described above)

My point was that, because of the way in recovery mode works in SGPro you might want to consider using only the “on camera” setting for the mount.

Communication traffic is not an issue. If it were you would be getting hard errors from your devices, like camera disconnects or hangs.

PC timing accuracy is not an issue for you either since you’ve already said you are satisfied with your current guiding.

The argument in favor of changing would be to remove the cable as a source of potential failure. The argument against changing: “if it ain’t broke don’t fix it.” Totally your call, no big deal either way. If you want to run an experiment, just try it (mount = ASCOM, aux mount = none); no need to physically remove the ST4 cable to try out guiding over ASCOM.

Andy

Thanks Andy. This is definitely an “ain’t broke don’t fix it” issue for me. However, as you say there is little downside to trying out ASCOM-only guiding so I will give that a run. I will also give the “Auto restore calibration” a try as well.

Thanks again to all for explaining this so well - I never really understood the ST-4 vs ASCOM guiding issue before this thread.
…Keith

1 Like

I was running what is now an elderly laptop with a singe core Celeron. Guiding was fine until the email program woke up and started downloading email…

I’m currently using a Core i5 with 4 Gb and it seems perfectly happy guiding, running SGP and CdC and surfing the web.

Chris

Im having serious trouble communicating… this should read "because of the way in recovery mode works in SGPro you might want to consider not using only the “on camera” setting for the mount.

Ha, funny Ken. Yes, after reading your response I thought of writing “Now I’m more confused than ever” but I decided to let it drop. Now everything is clear!
…Keith

Tonight, I eliminated the ST4 connector and started using only the ASCOM driver in PHD2. However, SGP errors saying that it cannot detect PHD2… PHD2 is guiding very well. I turned off the SGP guider but am still guiding no problem. For some reason, SGP tried to start the guider at the start of the sequence and before centering the target. I’m still trying to work this issue. I’m using SGP 2.6.0.25.

Regards,

Charlie

Here is a segment of the log.

01/19/18 19:48:47.560][DEBUG] [Sequence Thread] Dispatch loop: Received SGM_RUN_SEQUENCE…
[01/19/18 19:48:47.570][DEBUG] [Sequence Thread] GuiderCheck: Checking auto guider status…
[01/19/18 19:48:47.570][DEBUG] [Sequence Thread] GuiderCheck: Auto guider is not connected, attempting to connect…
[01/19/18 19:48:47.571][DEBUG] [Sequence Thread] GuiderCheck: Starting guider and connecting guider equipment for guider profile…
[01/19/18 19:48:47.586][DEBUG] [Auto Guider Equipment Connection Thread] PHD2: PHD2 is already open…
[01/19/18 19:48:47.588][DEBUG] [Auto Guider Equipment Connection Thread] Connecting to PHD2…
[01/19/18 19:48:47.595][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:48:47.595][DEBUG] [PHD2 Listener Thread] Attempting to connect to PHD2…
[01/19/18 19:48:48.596][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:48:48.603][DEBUG] [PHD2 Listener Thread] Failed to establish client connection to PHD2 using port 4400: No connection could be made because the target machine actively refused it 127.0.0.1:4400
[01/19/18 19:48:49.597][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:48:50.597][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:48:51.598][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:48:52.598][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:48:52.605][DEBUG] [PHD2 Listener Thread] Failed to establish client connection to PHD2 using port 4400: No connection could be made because the target machine actively refused it 127.0.0.1:4400
[01/19/18 19:48:53.599][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:48:54.599][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:48:55.599][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:48:55.606][DEBUG] [PHD2 Listener Thread] Could not etablish a connection to PHD2! Aborting…
[01/19/18 19:48:55.607][DEBUG] [PHD2 Listener Thread] PHD2 connection terminated…
[01/19/18 19:48:55.607][DEBUG] [PHD2 Listener Thread] Exiting PHD2 listener…
[01/19/18 19:48:56.600][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:48:57.601][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:48:57.601][DEBUG] [Auto Guider Equipment Connection Thread] Failed to connect to PHD2. Could not establish socket connection…
[01/19/18 19:49:02.605][DEBUG] [Auto Guider Equipment Connection Thread] Connecting to PHD2…
[01/19/18 19:49:02.606][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:02.606][DEBUG] [PHD2 Listener Thread] Attempting to connect to PHD2…
[01/19/18 19:49:03.607][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:03.609][DEBUG] [PHD2 Listener Thread] Failed to establish client connection to PHD2 using port 4400: No connection could be made because the target machine actively refused it 127.0.0.1:4400
[01/19/18 19:49:04.608][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:05.609][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:06.610][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:07.610][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:07.612][DEBUG] [PHD2 Listener Thread] Failed to establish client connection to PHD2 using port 4400: No connection could be made because the target machine actively refused it 127.0.0.1:4400
[01/19/18 19:49:08.610][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:09.611][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:10.611][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:10.612][DEBUG] [PHD2 Listener Thread] Could not etablish a connection to PHD2! Aborting…
[01/19/18 19:49:10.612][DEBUG] [PHD2 Listener Thread] PHD2 connection terminated…
[01/19/18 19:49:10.612][DEBUG] [PHD2 Listener Thread] Exiting PHD2 listener…
[01/19/18 19:49:11.611][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:12.611][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:12.611][DEBUG] [Auto Guider Equipment Connection Thread] Failed to connect to PHD2. Could not establish socket connection…
[01/19/18 19:49:17.598][DEBUG] [Sequence Thread] GuiderCheck: Could not start auto guider, aborting…
[01/19/18 19:49:17.616][DEBUG] [Auto Guider Equipment Connection Thread] Connecting to PHD2…
[01/19/18 19:49:17.616][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:17.616][DEBUG] [PHD2 Listener Thread] Attempting to connect to PHD2…
[01/19/18 19:49:18.618][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:18.619][DEBUG] [PHD2 Listener Thread] Failed to establish client connection to PHD2 using port 4400: No connection could be made because the target machine actively refused it 127.0.0.1:4400
[01/19/18 19:49:19.618][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:20.620][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:21.621][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:22.620][DEBUG] [PHD2 Listener Thread] Failed to establish client connection to PHD2 using port 4400: No connection could be made because the target machine actively refused it 127.0.0.1:4400
[01/19/18 19:49:22.621][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:23.622][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:24.622][DEBUG] [Auto Guider Equipment Connection Thread] Waiting for socket connection to PHD2…
[01/19/18 19:49:25.622][DEBUG] [PHD2 Listener Thread] Could not etablish a connection to PHD2! Aborting…
[01/19/18 19:49:25.622][DEBUG] [PHD2 Listener Thread] PHD2 connection terminated…

I think that somehow, the enable server became unchecked. @$*##%$!!!

Regards,

Charlie