Plate solve with sync turns off PEC playback on my CGX mount

[lowenthalm]

This is not in the bug section for reasons that will become apparent below!

I have been having trouble with PEC ever since I got my Edge 1100 and CGX mount (controlled with CPWI). PEC just didn't seem to be helping a lot of the time. I finally realized (very recently) that PEC playback was actually turning itself off after I performed certain actions. I missed this because I don't often need to go into "Config Mount" in CPWI very often, which is the only place that will tell you if the PEC is no longer playing back, as CPWI gives no indications in its main interface window about the state of PEC playback. With some experimentation, checking PEC playback status after each of my normal nightly operation steps when controlling the mount, I zeroed in on the cause: syncing the mount at the currently centered object's known coordinates.

If I plate solve with recenter only in SharpCap (set in SC settings), all is well. But, if I plate solve with recenter and sync mount, PEC playback is turned off. This is not a SharpCao bug, as far as I can tell: I did a plate solve with recenter only in SharpCap and then went to another app I use called AstroPlanner and used it to send the sync on object to the mount. Only the latter step turned PEC playback off. The great irony is that sync mount doesn't move the mount at all, so there is no reason for PEC playback to be knocked off-line.

Has anyone else had this problem? I can fix it once its happened by going to CPWI and opening config mount, turning PEC off, closing config mount, reopening config mount and turning PEC back on again (sure would be nice if there was just a "Seek Index" command! Not exactly useful in an automated workflow though, no? I have half a mind to have Celestron PECtool always running during a session so I can just use its magically simple "Seek Index" button to speed recovery after PEC playback has turned itself off - I'll try it tonight! I now suspect there are other events that can cause this problem so I will be keeping an eagle eye on PEC playback state from now on. I will report here if I find other cases where it turns off.

I think I saw a user reports somewhere of PEC seeming to be off when they thought it was on, and dismissed it to CPWI turning PEC off after a restart or some other anomalous event. I haven't had luck finding someone reporting exactly this though. My suspicion is that this may be a widespread problem, but that aggressive guiding is hiding the issue for many users. I am going to report this to Celestron (I have an open bug report on my poor tracking issues), but was hoping someone might have had a similar experience, or might try it out themselves to see if it happens on their mount too. It would be helpful when talking with Celestron to let them know its not just me.

[admin]

Hi,

interesting... I wonder if internally the mount tracks the PEC based on the RA value, and the code is not smart enough to handle a jump in RA caused by the 'sync' command being sent? I suspect if that's the case (or something similar) then the PEC is being turned off inside the mount firmware and the ASCOM driver (CPWI) doesn't know anything about it, so keeps the box ticked.

Just to be sure that I am understanding correctly - when you say you plate solve with recenter only, am I right in thinking that refers to setting the plate solve action to 'Offset the mount position to recenter the target', yes?

cheers,

Robin

[lowenthalm]

Hi,

interesting... I wonder if internally the mount tracks the PEC based on the RA value, and the code is not smart enough to handle a jump in RA caused by the 'sync' command being sent? I suspect if that's the case (or something similar) then the PEC is being turned off inside the mount firmware and the ASCOM driver (CPWI) doesn't know anything about it, so keeps the box ticked.

CPWI absolutely knows PEC playback is no longer active. I just have to open CWPI's "Configure Mount" dialog to see that its in this state. Its the only place to check for PEC playback status. The PEC enabled box checked is still check in this dialog box, but the status just below this is "Index not found" rather that "playback active". This is the state you see when you first turn on the mount and you have your saved pointing model loaded, but not synced yet - which ironically is what restarts PEC playback in the first place! I wonder if this might be a clue to how to sync the mount without destroying PEC playback...Hmm. I should try resyncing the mount on a star in CPWI after I already have the pointing model synced on a star and see if it zaps playback there too. If this doesn't break PEC playback, maybe there might be alternate way to sync the mount on an object, but I'll bet the pointing model can't be accessed through the CPWI ASCOM driver. In addition, its my understanding is that the CPWI ASCOM driver doesn't expose anything having to do with PEC PEMTool can't use this driver for anything useful and neither does PECTool, so sending a re-seek PEC index command is probably off the table.

Your firmware suggestion seems likely to me. I think I checked for a firmware update on their site fairly recently (for other reasons) and found that the latest version was released around 2020. I bought the mount in late 2021 so assumed it had the latest version installed. I should check on firmware versions again just to be sure. If this isn't just a glitch in my mount, its stunning to me that this is lurking in there and it appears people aren't aware. Mount syncing is a fairly common operation for users, I would assume.

Just to be sure that I am understanding correctly - when you say you plate solve with recenter only, am I right in thinking that refers to setting the plate solve action to 'Offset the mount position to recenter the target', yes?

cheers,

Robin

You are correct. This works around the problem. I ran all night last night in this mode on multiple targets and had much better RA tracking. I don't guide so this had been such an irritant that, I broke down and ordered an off-axis guiding rig a few weeks ago before I identified the culprit here. Hehe. I keep telling myself that I want to take exposures of 10 seconds and longer, so its still money well spent...

Interestingly, at first I thought that hitting slew limit caused the mount to lose the PEC index, which would make sense to me. However, last night I tested that out, again and found that this is not the case. I just hadn't yet identified that syncing the mount caused this and probably did a slew to new target and play solve/synced and then noticed the PEC playback was off and incorrectly attributed it to the RA slew limit being reached. Syncing the mount is the only action that I have found that breaks PEC playback.

[lowenthalm]

You can go to an object in CPWI (from the SIMBAD db, for example), center it or plate solve it offset only in Sharpcap, and then go back to CPWI and "add it to the pointing model" and PEC playback continues without an issue. So, it seems syncing the mount can be done without breaking PEC. Just not by anyone by Celestron.

[admin]

Hi,

actually the ASCOM code provides a few ways to send 'driver specific' messages from the application to the device. SharpCap doesn't currently use any of these, largely because they are rarely documented, so it's hard to tell that they are there (let alone how to use them properly) unless you have the specific type of hardware available for testing.

I have just had a dig in the CPWI Ascom driver to see if it has any commands like this, and it turns out it does...

Code: Select all

"Telescope:AuxCommand",
"Telescope:PecState",
"Telescope:PecPlayback",
"Telescope:PecRecord",
"Telescope:PecSeekIndex"
"Telescope:PecGetData",
"Telescope:PecSetData",
"Telescope:AxisPosition"

Interesting eh?

In theory I may be able to get the PecState before a sync and then re-start playback after a sync. It may need some experimentation and also I have to design some way to do this that doesn't make the rest of the code start to get very complex if I end up doing similar things for more mounts...

cheers,

Robin

[lowenthalm]

WOW. You need to let the PEMpro folks know about that one. I gave up (glad I was only using the demo version!) trying to get their software to work because it can only use the pre-CWPI ASCOM drivers, which I can't get to work under Windows 10. This forced me to finally figure out how to make the Windows 7 era PECTool from Celestron work under Windows 10 with my modern mount in order to do multi-PEC cycle averaging for PEC programming.

Having a warning that PEC isn't in playback mode in the status panel for the mount in SharpCap would be a pretty cool feature! I have had strange cases where playback doesn't start up when I initially align the mount, so there may be other situations where this can occur randomly. It may be a little mount specific though, so don't know if you would want to mess including a feature like that in SharpCap.

Before you try out anything, I just had a thought. When I got PECTool working, I switched to having CPWI operating the mount via the USB port on the mount so I could give PECTool direct and lone access to the hand controller via COM3. There is a chance that CPWI doesn't handle mount syncs properly if its connected directly to the mount USB, but might handle it properly when connected via the USB on the hand controller. It's probably a long shot, but I have seen some other weird differences between CPWI running the mount via hand contrloler USB port and via the mount USB port. I will test tonight. The software engineer in me is still alive in there somewhere, even though I retired a long time ago...

[lowenthalm]

Yeah, just tested it. A Plate Solve+sync in SharpCap still kills PEC playback when controlling the scope with CPWI through the hand controller USB. Didn't think it would make a difference, but I had to try. Now I go growl at Celestron and ask em if its my mount or their software/firmware that's broken. Or both. Should be interesting.

[admin]

Hi,

I think I will take this in small stages - the first one is that I will try to add some code to log the status of the PEC playback for CPWI connected mounts before and after the sync step. You can then test that out and see if it correctly reports that PEC is active before sync and inactive after. That would give me the information that I need to take the code further for an auto-recovery of PEC.

I am more reluctant to put anything specific in the UI for this sort of thing. It may just be one thing, but if it was just one thing for each different brand of mount then that would be a lot of things!

cheers,

Robin

[lowenthalm]

And it would be nice if celestron would fix it of course, but that won’t come quickly. I’d you decide to add something to probe this in log debug output, let me know and I will test it out.

I suppose it could be a problem with just my mount. It just seems so weirdly specific that it feels to me that it must be an actual bug. I haven’t seen anyone else concur that they see this. It looks like a good number of people have at least taken a look at this post.

I’ll send to celestron and cloudy nights and see what response I get.

[admin]

Hi,

so yes, I did add some logging each side of the Sync command to record the apparent state of PEC before and after. One thing that might be an issue is if the ASCOM driver reports the last known state rather than getting fresh data from the mount - if that's the case then asking straight away after the sync might not give us the new status and we might need to introduce a delay. I decided not to add that this time to try to be low impact in terms of changes related to this.

cheers,

Robin