Can't move more than a few degs in Dec: "position error" "clear servoerror"

[nakbrooks]

Frustrating day today. Thought I had the mount (DDM85 Pro) behaving well. Nicely balanced, tuning seemed fine and was able to move it fully in RA and DE using the Autoslew buttons and also via TheSkyX.

 

So I loaded up the camera and filter wheel, did a new home find, auto tune and balance but then discovered I couldn't move the Dec axis past the zenith southwards without getting autoslew "position error" and the "clear servoerror" message every few degrees.

 

Not sure what I've done. Only software change was the installation of MaximDL 5 and the FLI drivers for the camera and filter wheel.

 

I'll sleep on it and try again tomorrow.

 

Nigel

[nakbrooks]

Still can't sort this out. I've done multiple home finds (successful), I've auto tuned the servos and checked the balance, I've checked the limits (and also tried with limits off) but I still can't get the mount to rotate through the full DE range. I keep getting "Position Error" at more or less the same point. That point varies depending upon RA position and isn't consistent.

 

Is there anything obvious I am missing?

Edited July 27, 2013 by nakbrooks

[GeorgeCarey]

It might be useful to turn on the logging feature. I can't recall exactly where it is in the menu system. Mount... servos I think.

That will enable you to read the log and see what the current consumption is. Often before an error the current rises.

[cfm2004]

Have you disconnect the power? 

 

Cristina

[nakbrooks]

I have still not been able to resolve my problem (not being able to move the DE axis through its full range without Position Error).

Here is what I did to replicate the problem (times are given for ease of reference to the attached logs):

 

I recycled the power to the mount and also re-booted the computer before running this test.

 

13:54 Positioned mount manually at park position (RA horizontal, with OTA on West side and DE pointing approximately at Pole)

 

13:55 Start Autoslew

 

13:56 Start motors (does Autofind)

 

13:57 Stop motors

 

13:57 Move mount by hand to approximate Homefind position (RA stays horizontal, DE just south of zenith, OTA on West)

 

13:58 Restart motors

 

14:00 Do Homefind (finds both axes quickly)

 

At this point RA is horizontal, with the OTA on the West side and DE is slightly North of Zenith. Autoslew coordinates are RA 10h52m24.75s; DE +51deg33'50''. Siderial tracking is on.

 

14:04 Using the Autoslew Move-Controls, I replicate the problem by moving DE South, through zenith. Speed is the default 5.00deg/sec. Slew stops with Position Error (autocleared) reported. I try again. Second Position Error, this time with "Clear Servoerror" warning. Autoslew coordinates are RA 10h54m30s; DE +41deg24'30''.

 

14:08 I clear the Servoerror. I return the DE to the zenith then try and move DE south again at slower speed (0.94deg/sec). Almost immediately the same problem occurs: Slew stopped with Position Error (autocleared). I try again, with immediate Position Error with "Clear Servoerror" warning. Autoslew coordinates are now RA 10h57m45s; DE +51deg09'25'' (note that the errors occurred at different points).

 

14:11 I clear the Servoerror; turn motors off and exit Autoslew.

 

The Servo log is attached. Look at the very large position errors at 14:04:38.747 and 14:04:43.801 (relating to my two DE slew attempts at 14:04).

 

The message log is also attached.

 

I am running Autoslew version 5.1.1.6 with ACC. The mount is perfectly balanced according to the Autoslew Servo Setup balance utility (the red bars touch for both axes). I have run Fast Tuning and also High PerformanceTuning (which did not improve the Fast Tuning settings). I have not manually adjusted the settings provided by Auto Tuning.

 

The DIP values set by Auto Tuning for DE are 2940, 134709, 19.8 for siderial speed; 850, 39000, 4.0 for both medium and full speed. For RA the DIP values are 2940, 18000,3.6 for siderial speed and 1322, 60000, 6.0 for both medium and full speed. Noise filter is on for both DE and RA and P is stuck to I for both axes.

 

My limits are set at: 5.0 Min altitude above horizon; 90.0 how far I can go through the meridian (90 because I am using the equatorial pier so do not need to flip) with minimum flip distance kept at the default 3.8. Check Limits is turned on (I have tried with it turned off but this makes no difference). Flip Option is set to Prefer West. My location is correctly set.

 

My PC platform is Windows 7 Pro SP1 32bit with all Microsoft updates applied as at 16 July (I have done no Windows updates since installing Autoslew to avoid causing problems).

 

I am using the DDM85 Premium mount with the DDM85K equatorial pier. My payload (excluding counterweights) is about 80kg.

 

There are no physical obstructions (cables, etc) that might be preventing free DE movement.

 

At present I have not done a polar alignment, although the ASA equatorial pier is designed for my specific latitude and is aligned to within 2 deg of north, so I am aligned to within a degree or so in both axes and my problem is certainly not caused by misalignment.

 

Any advice on where my problem may lie would be very welcome as at present I cannot move the DE axis south of the zenith with the OTA on the west side.

 

Nigel

ServoLog.txt

MessageLog.txt

Edited July 28, 2013 by nakbrooks

[GeorgeCarey]

There seems to be a readint16 read error right at the start. I have no idea what this means but it looks suspicious.

Have you ever tried a manual home find?

The magnetic angle is stored in the registration key and is used automatically when you do a manual home find.

[nakbrooks]

At George's suggestion I repeated the test but doing a manual Homefind instead of an automated one. Basically it seemed to make no difference so I still have my problem (not being able to move the DE axis through its full range without Position Error).

 

Here is what I did (times are given for ease of reference to the attached logs):

 

I turned off all power to the mount and the computer, then powered up the mount (not the motors) and re-booted the computer before running this test.

 

08:43 Positioned mount manually at park position (RA horizontal, with OTA on West side and DE pointing approximately at Pole)

 

08:44 Start Autoslew

 

08:45 Start motors (does Autofind)

 

08:46 Stop motors

 

08:47 Move mount by hand to approximate Homefind position (RA stays horizontal, DE just south of zenith, OTA on West)

 

08:48 Restart motors

 

08:49 Do manual Homefind for RA (using menu Servo Setup/Homefind settings for Axis RA/Find Reference Mark). Reference Mark is found OK.

 

08:50 Do manual Homefind for DE (using menu Servo Setup/Homefind settings for Axis DE/Find Reference Mark). Reference Mark is found OK.

 

08:51 In Servo Setup I Save to Ini and exit.

 

At this point RA is horizontal, with the OTA on the West side and DE is slightly North of Zenith. Autoslew coordinates are RA05h48m14.80s; DE +51deg11'59''. Siderial tracking is on.

 

08:56 Using the Autoslew Move-Controls, I try to replicate the problem by moving DE South, through zenith. Speed is the default 5.00deg/sec. SAME PROBLEM OCCURS: Slew stops with Position Error (autocleared) reported. I try again. Second Position Error, this time with "Clear Servoerror" warning. Autoslew coordinates are RA 05h48m17.43s; DE +41deg18'34''.

 

08:58 After clearing the Servoerror. I return the DE to the zenith then try and move DE south again at slower speed (0.94deg/sec). Almost immediately the same problem occurs: Slew stopped with Position Error (autocleared). I try again, with immediate Position Error with "Clear Servoerror" warning. Autoslew coordinates are now RA 05h48m20.36s; DE +51deg22'08'' (note that the errors occurred at different points).

 

09:01 After clearing the servo error I turn off the motors, manually move DE just south of the zenith, turn on the motors again and try an automated Homefind to see if it results in different coordinates. Both axes are found OK. Autoslew coordinates are RA 5h56m47.66s; DE +51deg33'50'' (somewhat different to the coordinates after the manual Homefind, above).

 

09:04 Just in case it now works I try again to move DE South past the zenith. Same problem.

 

09:05 I turn motors off and exit Autoslew.

 

The Servo log is attached. Note the following:

 

1. The readInt16 error spotted by George is still present.

 

2. The magnetic angles found by Autofind are very different to those found yesterday (particularly Axis 1).

 

3. The manual Homefind corrected the magnetic angle by a very large amount for RA (339) - but it still ends up substantially different to yesterday.

 

4. Look at the very large position errors at 08:58:22.816 and 08:58:30.070 (relating to my second, slow-speed, DE slew attempt at 08:58). The position errors for the first, higher-speed, DE slew attempt at 08:56 were much lower.

 

5. My automated Homefind at 09:01 resulted in no change to the RA magnetic angle and only a -1 change to the DE magnetic angle.

 

6. Look at the very large (3386.05 arcsecs) position error at 09:04:47.619 (relating to my final DE slew attempt at 09:04).

 

The message log is also attached.

 

Just to repeat my environment details:

 

I am running Autoslew version 5.1.1.6 with ACC. The mount is perfectly balanced according to the Autoslew Servo Setup balance utility (the red bars touch for both axes). I have run Fast Tuning and also High PerformanceTuning (which did not improve the Fast Tuning settings). I have not manually adjusted the settings provided by Auto Tuning.

 

The DIP values set by Auto Tuning for DE are 2940, 134709, 19.8 for siderial speed; 850, 39000, 4.0 for both medium and full speed. For RA the DIP values are 2940, 18000,3.6 for siderial speed and 1322, 60000, 6.0 for both medium and full speed. Noise filter is on for both DE and RA and P is stuck to I for both axes.

 

My limits are set at: 5.0 Min altitude above horizon; 90.0 how far I can go through the meridian (90 because I am using the equatorial pier so do not need to flip) with minimum flip distance kept at the default 3.8. Check Limits is turned on (I have tried with it turned off but this makes no difference). Flip Option is set to Prefer West. My location is correctly set.

 

My PC platform is Windows 7 Pro SP1 32bit with all Microsoft updates applied as at 16 July (I have done no Windows updates since installing Autoslew to avoid causing problems).

 

I am using the DDM85 Premium mount with the DDM85K equatorial pier. My payload (excluding counterweights) is about 80kg.

 

There are no physical obstructions (cables, etc) that might be preventing free DE movement.

 

At present I have not done a polar alignment, although the ASA equatorial pier is designed for my specific latitude and is aligned to within 1 or 2 deg of north, so I am aligned to within a degree or so in both axes and my problem is certainly not caused by misalignment.

 

Any advice on where my problem may lie would be very welcome as at present I cannot move the DE axis south of the zenith with the OTA on the west side.

 

Nigel

ServoLog2.txt

MessageLog2.txt

[P.Keller]

you said that you have perfect balance but did you check the balance http://www.astrooptik.com/asa/Balance.pdf ?

You can easily have balance in one position but have problems in another position, especially with heavy CCD or filterwheel you need to add a counterweight opposite to the CCD on the tube.

The sensorless find looks like the tube is moving a little in one direction while you make it.

The velicity limit in the servolog means you moved the mount by hand to fast. It then looses the encoder position and thus the right magnetic angle.

The movement in DEC during sensorless find is a little small. Use higher current here.

 

The magnetiv angle it writes in the LOG can be different each time because it depends where you have your mount when you power up. Having different values here each time is not a problem. A problem however is, when this angle is corrected by a huge amount after homefind.

This means the magnetic angle is found wrong.

It should be between 340 (=-20) and +20 degree, not more.

 

So right now I would guess its a balance problem (this is the problem in 90% of all support cases we have) or it could as well be a tuning problem.

If you like, I can take a look via teamviewer. Please then contact me via p.keller@astrosysteme.at

 

P.S.

Did you change something on USB when you added the camera ?

08:44:27.556: readInt16 read error  2x. Received error# from ftdxx.dll was 3072
08:44:27.571: Now trying ResetDevice, this returned  0
08:44:27.587: readInt16 after ResetDevice still not working, returned error#  3072

 

this does not look nice, there seems to be a USB problem.

[nakbrooks]

Thanks Paul. A lot for me to chew over there. I agree it might be a balance issue. I'll try in different positions and see what I can do.

 

Regarding USB, the camera USB is connected (to the DDM85 DE hub) but the camera power cable is disconnected (I wanted to discount trailing cables as a possible factor).

 

Let me recheck balance and if there is still a problem we can maybe do a remote session.

 

Thanks

 

Nigel

[nakbrooks]

Paul

 

I think I have found the culprit - it is the FLI filter-wheel, which is heavy and off-centre.  I am balanced in some orientations but not others.  I used the rotator to maintain the filter-wheel's centre of gravity in the same position relative to the Axes while testing balance in numerous orientations.  The maximum out-of-balance was 1 amp in each axis (most of the time it was less than 0.5 amps).  I presume 1 amp is manageable? 

 

I will need to find a way of counter-weighting the filter wheel.  As I have a rotator I will need to attach the counter-weights to the filter wheel itself, or the camera - I'll have to work out how to do that (they are a bit expensive to be drilling holes in !!).

 

Regarding the readInt16 error, I am getting frequent, and apparently random, Device Error messages in ACC.  These can usually be reset by clicking the message but recur every few minutes.  Are these related to the readInt16 error?  Are there any diagnostics I can run to find the cause of the Device Errors?

 

Many thanks

 

Nigel

[nakbrooks]

Sorry Phillip - keep calling you Paul!  I apologise.

 

Nigel

[P.Keller]

Paul

 

I think I have found the culprit - it is the FLI filter-wheel, which is heavy and off-centre.  I am balanced in some orientations but not others.  I used the rotator to maintain the filter-wheel's centre of gravity in the same position relative to the Axes while testing balance in numerous orientations.  The maximum out-of-balance was 1 amp in each axis (most of the time it was less than 0.5 amps).  I presume 1 amp is manageable? 

 

I will need to find a way of counter-weighting the filter wheel.  As I have a rotator I will need to attach the counter-weights to the filter wheel itself, or the camera - I'll have to work out how to do that (they are a bit expensive to be drilling holes in !!).

 

Regarding the readInt16 error, I am getting frequent, and apparently random, Device Error messages in ACC.  These can usually be reset by clicking the message but recur every few minutes.  Are these related to the readInt16 error?  Are there any diagnostics I can run to find the cause of the Device Errors?

 

Many thanks

 

Nigel

 

I think the rotation of the assymetric filter wheel by the rotator should be managable by the mount. +-1A is OK.

But during sensorlessfind the balance should be quite well because otherwise the back and forth motion keeps the mount also to travel in one direction during this measurement and this spoils the result.

 

It is very important that the focuser, CCD and filterwheel is balanced. This is a lot of weight. Maybe you have to add a counterweight to the tube.

 

Regarding the ACC device errors, this is caused when the USB port is lost. Can you try to connect it to another USB outlet of your computer or another Hub or try another cable ?

[nakbrooks]

Phillip

 

Is there any way I can tell which USB is causing the ACC Device Error problem? There are 4 possibilities:

 

1. Cable from PC to mount Data socket on RA axis (this is a 3m Lindy USB2 cable - the ASA-supplied one was a bit too short).

 

2. Cable from PC to mount Hub socket on RA axis (also 3m Lindy).

 

3. Internal mount cabling connecting RA Hub socket and DE hub.

 

4. Cable from DE hub to socket on side of OTA for the SM2A controller (uses the ASA-supplied spiral cable).

 

Obviously I can experiment with switching cables but as the problem is intermittent it would be good to know for sure which cable/socket is at fault.

 

Both the Data and Hub RA sockets are connected directly to the PC - the only external hub is the ASA one built into the DE axis.

 

Thanks

 

Nigel

[GeorgeCarey]

Good to see that you are getting somewhere. My system is difficult to balance because moving the scope a millimetre in the tube rings is sometimes too much. I have invented a magnetic balance weight which makes the balancing process very easy and accurate. I have taped a magnetic stainless steel plate to the side of the scope, and made a lead counterweight. Eight small neodymium magnets are glued into the counterweight and a layer of thin felt applied. The counterweight slides easily up and down the steel plate, but the magnets hold it firmly in place.

I have the steel strip over to one side, to balance the offset weight of the camera and guide lodestar.

 

Edited July 30, 2013 by GeorgeCarey

[nakbrooks]

Ingenious solution George.  My main OTA is heavy (70kg including imaging equipment) so I get fore and aft balance by moving the secondary OTA in its rings.  As the secondary is light by comparison this gives me fine enough adjustment.

 

My OTA is a classical cass so everything else hangs off the back end, not the side (in many respects easier to balance).

 

My main issue is balancing the camera/filter assembly.  Because I have a rotator, and because the heavy filter wheel is offset to one side of the camera, the balance changes as I rotate, even if the RA and DE axes stay put.  Essentially I have to balance the camera/filter assembly independently of the rest of the equipment.

 

The Proline has 4 bolt holes at each corner, only two of which are used to secure the filter wheel.  The vacant pair are on the opposite side to the filter wheel.  My plan is to have a strip of steel machined to bolt onto the camera using those bolt holes and threaded at the side with holes at 2cm intervals or so (to give me fore and aft adjustment), into which I can screw counterweights salvaged from my old Meade LX90.  If this works I'll post photos. It will take a while though as I can't get the machining done locally to here.

 

I'm also waiting for a further counterweight to arrive from ASA - at present I have a roll of spanners strapped around the counterweight arm as a temporary fix - doesn't look very elegant but it works!

 

Nigel

[DaveK]

Nigel wrote: "...because the heavy filter wheel is offset to one side of the camera, the balance changes as I rotate..."

 

This is precisely why I purchased the FLI CL1-10 Centerline Filter Wheel. It is symmetrical and remains in balance with my Proline PL16803 camera when rotated via the PIR on my RCOS telescope.

 

I also have an FLI ML8300 with a CFW2-7 and it is difficult to balance in all positions.

[nakbrooks]

I've posted details of my solution for balancing the filter wheel in the tips and tricks section.

[GeorgeCarey]

Neat solution! Are you getting smooth movement in dec now?

[nakbrooks]

Yes, it was a balance issue now resolved.