Repeated slew after message slew complete appears - although scope reached position

[Peter Jankowski]

Hi,

Currently I’m testing ACP 7.1 on a new Windows 7 computer. I’m on the way from Win XP to Win 7. Compared with the old PC unfortunately ACP isn’t any more working properly like before.

As camera I’m using for these tests a Canon 50D. For sure I’ll substitute this camera with a CCD soon, but for testing it is okay.


Now the Problem:
A repeated slew happens after the message “slew complete” appears although the scope has already reached the position to capture the image. This means that this slew moving of the Telescope is on the captured images.

The log file shows nothing wrong. But on the ACP control window after the messages “wait for slew to complete” and “slew complete” (the scope really stopped slewing before) the slew indicator flashes again and the scope is slewing again unnecessarily.


I’ve compared the settings of ACP on Win XP to Win 7, but I can’t see a difference. MaxIm is the latest version.

Any help is highly welcome.

[Peter Jankowski]

Hi All,

Yesterday night I’ve continued my test of the new Win 7 PC.


Yet I have found that the described error occurs sporadically - sometimes it happens, sometimes it doesn't. That means for example:

1. Test:
Image to plate solve and several test images are well done -> without extra slew during capturing

2. Test:
Image to plate solve is okay. At the beginning of capturing all images a slew for some seconds starts (without reason in my opinion).

3. Test:
During image to plate solve the scope starts to slew for some seconds, but all images of the object are fine.


To point it out again:
The scope starts to slew again at the beginning of any image acquisition (plate solve or objects) for some seconds sporadically.



I’m confused and frustrated. Again – sometimes it happens and sometimes it doesn’t.


Really, any help is welcome.

[Dick Berg]

Hi Peter, Sorry this is hard for you right now. Generally, here's what happens when you are imaging:

- Slew to target (may not be centered when slew stops; depends on quality of the mount)
- Take a pointing image and solve it. If the offset is greater than the "Max pointing error" (ACP Pref/PinPoint tab - middle of that window), ACP recenters the telescope with a short slew. If the pointing image doesn't solve, ACP does a small offset slew to an adjacent FOV and takes another pointing image and solves it. If the offset is greater (as above) it recenters and slews back to target. If the second pointing image doesn't solve, ACP slews back to original target location even if it is off center. These recentering slews should be small ones, only a couple arcminutes at most, probably.
- Take the target image. Solve it, save it.Again, i f the solved image offset is greater than the "Max pointing error", ACP does another recentering slew.
- If you are taking more than one of this target, take the next image, solve it, save it and do recentering if it off by more than the "Max pointing error."
- At some point, slew to next target. Begin the process as above.

A couple things to note.
- small slews between images are possible and normal. Depending on how the derived image center compared to the target coordinates, slews could happen sometimes and sometimes not.
- Slews should have stopped before images are taken. If this is happening, then there's may be some issue with your mount driver. ACP waits for the slews to stop.

Look again at the ACP Prefs/PinPoint tab, and check your value of the "Max pointing err." I set mine at 0.5 min (that's arcminutes) for my Meade 12" LX200 on the Meade mount. Your value for this may be set too low, in which case you will find that it is constantly recentering after almost every image or pointing image.

[Bob Denny]

This is the Meade LX200? Do you perhaps have "consistent approach" on? And what kind of LX200 (classic, GPS)?

[Peter Jankowski]

Hi Dick,

tanks for your help.

I agree with your statements to the process. It makes sense.

I've changed the "max pointing error" in ACP from 3 to 12 (arcmin) to be sure that the effect isn't caused by this parameter.
--> No change, again slew happens sporadically after the image acquisition started.

I've done a series of images with MaxIm on the new computer with Win 7 (without ACP, except that the scope is connected via ACP).
--> All images are well done! That means without slew after the image acquisition started.
--> By the way I've done dozens of image aquisitions with more than 12 images in series with MaxIm only without any problem.

Therefore, I assume that the mount is okay. The error happens only if I take images within ACP. And it doesn't matter if the images are made with the script "AquireImages" or via WEB.


Today I'll do the same test on the old computer with Win XP to verify if the error happens here too - although I didn't saw this error. If the error does not occur, then the new system contains the problem.


Any further help is welcome.

[Dick Berg]

Bob, his signature block indicates that he has a 10micron GM 2000 HPS (GEM) mount. He's just using the Meade OTA.

[Bob Denny]

Bob, his signature block indicates that he has a 10micron GM 2000 HPS (GEM) mount. He's just using the Meade OTA.

Oh, I missed that. I was fried after 6 hours on live support yesterday :-)

[Bob Denny]

Peter -- This is almost certainly going to be a driver/controller bug... now on to proving it. Yeah, it always starts with "It works with ___ but not with ACP", in this case MaxIm. Anyway, let's instrument your setup.

1. Please open up the Pipe Connection Tool from the Windows Start menu, All Programs, ASCOM Platform, Tools.
2. Set it up to use your mount as its telescope (you'll see the same ASCOM Chooser as always, choose your mount type then click OK).
3. Now in ACP, change it to use the Pipe Connection Watcher as its telescope, and go through the telescope change boxes/process.
4. Click OK in the Pipe setup window and check all of the trace option checkboxes.
5. Now do Telescope Connect in ACP.
6. If you use the Slew or Sync (catalog) button and that form, will the problem happen? If so use that to make it do its double slew. Otherwise, do whatever you need to do to make it happen. You might be able to do this during the day by turning on Simulated Images in the ACP Prefs General tab.
7. Once you have been able to create some double-slews, shut everything down and go get the Pipe.log file from C:\Program Files\Common Files[ (x86)]\ASCOM\Telescope.
8. Attach that pipe.log trace file to your reply here.

[Dick Berg]

Peter, Just a few questions to clarify things. Which telescope are you using with your camera? (i.e. what's your image scale and extent?) Are all three of your telescopes mounted on the mount at the same time? Are you using one scope for pointing and guiding, and another at the same time for imaging? Which ASCOM driver do you select in the telescope setup chooser?

Regarding the tolerance, at 3 arcminutes I would think you 'd have no trouble with too-aggressive recentering. I thought at first you might have had that set to something like 0.1 arcminutes, though from the specs I saw your mount could probably meet that tolerance.

So the question is, "what would cause the telescope to slew after you've started an exposure." Don't know - it shouldn't happen.

Here's another general comment. If you have ACP running, in the customary setup you would have ACP connected to the manufacturer's ASCOM-compatible telescope driver - in the telescope setup chooser. You would also set up your camera in MaxIm through the Camera Control panel, choosing the appropriate item in the drop down for the camera model. And finally, you would NOT connect MaxIm to the telescope (in the Observatory control panel) because ACP is already controlling the telescope. If you have ACP and MaxIm both connected to the telescope driver at the same time, it's conceivable that there's some peculiar interaction through the ASCOM driver causing the problem you're experiencing. If you haven't already, try running with ACP connected to the telescope and MaxIm not connected to the telescope. If you've already set it up this way, and it doesn't stop the problem, then just disregard this whole paragraph.

EDIT: I see Bob has already given you a suggestion for getting at this problem. You can still think about what I've said, but I would go first through Bob's process.

[Bob Denny]

Dick, i should have said "Thanks for your help!!"