Meridian flip with OAG - is there a way?

169 views
Skip to first unread message

sar...@gmail.com

unread,
Apr 16, 2024, 4:45:11 PM4/16/24
to Open PHD Guiding
I've been using PHD2 successfully for a few years. I use an OAG on a Celestron C8 with 2032mm F.L.  At f/10 prime focus the OAG has a field of only about 8' . I have written software to pre-select a good guide star and pre-compute the position angle of the OAG necessary to catch that star.  Often there is only 1 good guide star.  So when I cross the meridian, I rotate the OAG (and camera) 180 deg to re-capture the guide star.  I have a home made position angle scale on the OAG, but I think I can rotate it with an accuracy of a degree or so.

My problem is that I haven't been able to find any way to avoid doing another calibration after the meridian flip.  I tried using the meridian flip wizard - it is never satisfied. I've tried explicitly telling PHD2 to flip Dec. or not.  Does my practice of rotating the whole tail piece 180 deg. preclude  having PHD2 handle this the way I want?  I guess both axes are reversed.  (I am using a ZWO AM5 mount with ASCOM interface and NINA+PHD2.)

bw_m...@earthlink.net

unread,
Apr 16, 2024, 6:16:53 PM4/16/24
to open-phd...@googlegroups.com

This isn’t going to work unless you have a way to connect PHD2 to a rotator or otherwise report what the rotator angle is.  It sounds like you are rotating the guider assembly by hand, is that correct?  If so, there’s probably a way to avoid the re-calibration.  Connect PHD2 to the ASCOM rotator simulator and use the simulator UI to specify what the angle is.  In other words, stop guiding, meridian flip, rotate the OAG by hand, enter the new angle into the rotator simulator UI, then re-start guiding. That’s how we test various rotator functions in PHD2 without actually having one.  As it is, PHD2 has no way to know that you’ve manually rotated by 180 degrees.

 

Bruce

--
You received this message because you are subscribed to the Google Groups "Open PHD Guiding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to open-phd-guidi...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/open-phd-guiding/98a97a3d-748d-4014-9058-8d4f53a796a5n%40googlegroups.com.

sarg314

unread,
Apr 16, 2024, 7:16:31 PM4/16/24
to open-phd...@googlegroups.com
Yes I rotate the guider AND the camera by hand (camera is mounted on the OAG).
So, you are saying that PHD2 can use a real mount and real guider and a simulated rotator simultaneously?



--
Tom Sargent

bw_m...@earthlink.net

unread,
Apr 16, 2024, 7:28:40 PM4/16/24
to open-phd...@googlegroups.com

Yes, but you have to take responsibility to enter the correct angle into the ASCOM simulator UI.  You have to use the ASCOM rotator simulator, not the built-in simulator that’s part of PHD2.

sarg314

unread,
Apr 16, 2024, 11:00:12 PM4/16/24
to open-phd...@googlegroups.com
I've know the ASCOM built-in simulator.  How do I access the rotator simulator you are referring to.?



--
Tom Sargent

Brian Valente

unread,
Apr 16, 2024, 11:11:39 PM4/16/24
to open-phd...@googlegroups.com
it's in the equipment setup under More Equipment...

image.png



--

sarg314

unread,
Apr 17, 2024, 1:27:30 PM4/17/24
to open-phd...@googlegroups.com
Great, thanks. I'll try it.



--
Tom Sargent

sarg314

unread,
Oct 30, 2025, 6:59:49 PM (7 days ago) Oct 30
to Open PHD Guiding
I had trouble with this issue in Apr. 24 and got distracted and am trying to get it to work again.  I added the rotator simulator as you indicated to the existing profile.  It says it connects.  But I don't see any rotator user interface appear where I can enter a rotation angle.  When I first tried this back in 2024, I recall seeing a rotator user interface, but not now.  Looks like a step backwards.  I thought maybe I was missing an ASCOM driver, but the right simulator appears in the drop down list, so I think that indicates it is available.
phd2RotSim.png

Bruce Waddington

unread,
Oct 30, 2025, 8:39:24 PM (7 days ago) Oct 30
to Open PHD Guiding
You haven't sent us any log files so I have no way to know what release of PHD2 you're using.  What I can tell you is that it works fine on 2.6.13dev7 and probably on the older releases (I just tested it).  PHD2 doesn't control the appearance of the ASCOM rotator simulator window - it is automatically launched when PHD2 connects to that simulator and will show up on the Windows taskbar.  Obviously, you must have PHD2 connected to the rotator simulator. Perhaps you were running with a dual display setup last year and no longer have that - then the ASCOM simulator window might be bound to the missing display.  Or perhaps it is simply minimized and you need to click on the taskbar icon to view it. Or perhaps it is just lying underneath all these other windows you have floating around.  In any case, I would say that any "step backwards" is probably happening on your end.  If you want to be absolutely safe, update to the 2.6.13dev7 release of PHD2 and then you'll be running with the same software I just re-tested.

Regards,
Bruce

sarg314

unread,
Oct 31, 2025, 7:56:21 PM (6 days ago) Oct 31
to Open PHD Guiding
I apologize for not following through on this back in 2024.  Any step backward is certainly mine.  I didn't attach a log file yesterday because I thought I hadn't caused any log-able events to happen, but I didn't think about version info. Both yesterday's log and todays are attached. I tried doing a PHD2 update yesterday and it told me I was up to date.

I never used a dual display with ASCOM or PHD2 - always just  a laptop.  I've checked under every window and in every workspace.   In the past I've had programs that insisted on opening in the first workspace, so I would miss them.  Today when I did the connect-all it ALSO opened a text terminal (see attached screenshot). If I look in the task manager I see an entry for ascom.alpaca.simulators, which I assume is connected to the terminal window.  (Maybe that terminal was minimized in the taskbar yesterday but the terminal itself just wasn't open for some reason and I didn't notice.) I don't know what to do with the terminal window and assume I'm not supposed to do anything with it.  If you look in yesterday's screenshot you will also see a tiny window in the lower left which says "ASCOM.ASCOMOmniSim.CameraDriverServer".  It's not a GUI. If I expand it it says it's a server.  I wish I'd captured the whole screen yesterday - it would show the task bar.  So I still can't find a rotator simulator GUI.

If I tell PHD2 to disconnect all it displays an error message at the top of its window that says "ASCOM Driver problem -- Cant get rotator position. (Driver error preparing to call Position)  The RPC Server is unavailable".  An attempt to connect all again produces the same error.  If I terminate PHD2 and restart it, then I can do that first connect all with no error message, but only the first one.

I opened ASCOM diagnostics and it offered to update me from platform 7.0 to 7.1.  I've suspected there might be a ASCOM issue, so I updated it.  After that PHD2 behaves as before, connecting to the rotator, the task manager still shows ASCOM.ALPACA.Simulators.   PHD2 says the rotator simulator.NET is connected.  But now there is no alpaca terminal window opened (nor minimized)  and still no rotator GUI anywhere I can find or rotator icon minimized in the task bar.  However, I do note that now I can disconnect all and connect all in PHD2 repeatedly with no error messages.  So maybe there was something wonky with my ASCOM installation.

I'm pretty sure this is something about my operating environment, but I'm up to date on ASCOM and PHD2.  I don't know where to look next or what to re-install (maybe install PHD2 anyway?). Thanks for your help.

PHD2_GuideLog_2025-10-31_154216.txt
PHD2_GuideLog_2025-10-30_143732.txt
Screenshot 2025-10-31 155503.png

Michael Waring

unread,
Nov 1, 2025, 6:39:09 AM (5 days ago) Nov 1
to Open PHD Guiding
You've sent the experts two empty GuideLogs labelled  14:37:32  - you weren't guiding that afternoon !

And no DebugLogs,.

Follow the Upload instructions in the Help menu.

Michael
Wiltshire UK

  .


sarg314

unread,
Nov 1, 2025, 12:42:37 PM (5 days ago) Nov 1
to Open PHD Guiding
So sorry.  I never think of the debug logs.  
PHD2_DebugLog_2025-10-30_143732.txt
PHD2_DebugLog_2025-10-31_154216.txt

Bryan

unread,
Nov 1, 2025, 3:31:24 PM (5 days ago) Nov 1
to Open PHD Guiding
It really is easier for everyone, including you to use the built-in log uploader as others have suggested.  Then you can ensure that you pick a date when issues arose as well as endure that Guide and Debug logs are uploaded.

Bryan

Bruce Waddington

unread,
Nov 2, 2025, 12:47:48 AM (4 days ago) Nov 2
to Open PHD Guiding
I'm traveling at the moment and not in a position to do a lot of debugging.  I think you've inadvertently driven into the ASCOM Alpaca swamp which includes a rewrite of the Rotator simulator and, evidently, a new UI paradigm that uses a separate control window on the Windows toolbar.  The debug log show the Rotator simulator has not been started even though PHD2 has connected to it.  I won't be able to look at this until I get home and can install ASCOM 7.1 in a software "sandbox" that won't screw up the highly reliable previous ASCOM release I'm using.  If you want to work on this yourself, try to find some ASCOM documentation about how this thing is supposed to work or, better still, download and install the older Rotator simulator and use that.

Bruce

sarg314

unread,
Nov 2, 2025, 11:30:31 PM (3 days ago) Nov 2
to open-phd...@googlegroups.com
Bryan:
OK, I'm looking into installing the previous version of the alpaca simulator.  I looked around and found that I presently have alpaca version 0.5.  I was able to find alpaca version 0.4 and downloaded the zip file from the ASCOM github.  I only use windows to run and PHD2 and NINA, so I don't really know much about operations like this on windows (I normally use Linux). The ascom.alpaca.simulators.net80.zip file which I downloaded from github appears to have the same stuff in it as the existing directory
C:\ProgramFiles\ASCOM\OmniSimulator\.  

The windows control panel uninstaller seems only to offer me the option of uninstalling all of ASCOM 7.1, so I'm guessing I shouldn't try to uninstall the rotator simulator.  Should I just make a new OmniSimulator\ directory and unpack the zip file into that?  No installer or uninstaller action?



--
Tom Sargent
Reply all
Reply to author
Forward
0 new messages