Re: Pulse Guiding - My ASCOM Log


Ross Salinger
 

2018/01/14-22:08:25:525:

3.829124996

24.20279793

0.242687337

0.012212262

5474418

-10

2.199157167

39715141.31

4605372.075

0

2018/01/14-22:08:25:712:

3.829126254

24.20281069

0.160770439

-0.033634147

5474637

-10

2.199218283

39715308.31

4605378.075

0

N

310

2018/01/14-22:08:25:837:

3.82912442

24.20281082

0.006786989

4.605144337

5474746

-10

2.19924884

39715398.31

4605369.075

0

2018/01/14-22:08:26:009:

3.829125644

24.20306162

0.07481398

3.704257622

5474965

-10

2.199309956

39715565.31

4605364.075

0

2018/01/14-22:08:26:369:

3.829126054

24.20368837

0.146744001

1.452929586

5475293

-10

2.199401629

39715819.31

4605347.075

0

2018/01/14-22:08:26:509:

3.829125854

24.20388907

0.137522985

0.732042844

5475512

-10

2.199462745

39715990.31

4605348.075

0

2018/01/14-22:08:26:853:

3.829125262

24.20401471

0.151516681

0.280714721

5475840

-10

2.199554418

39716247.31

4605347.075

0

2018/01/14-22:08:27:009:

3.829125133

24.20403989

0.09976857

0.190269307

5475950

-10

2.199584976

39716333.31

4605348.075

0

2018/01/14-22:08:27:337:

3.829125985

24.20407784

0.146009418

0.053941149

5476278

-10

2.199676649

39716586.31

4605346.075

0

2018/01/14-22:08:27:509:

3.829124462

24.2040781

0.063814933

0.098058396

5476496

-10

2.199737764

39716760.31

4605349.075

0

2018/01/14-22:08:27:838:

3.829125237

24.20409099

0.105780349

0.006726154

5476825

-10

2.199829437

39717014.31

4605353.075

0

2018/01/14-22:08:28:010:

3.829122688

24.20409112

-0.031876592

0.006284767

5476934

-10

2.199859995

39717106.31

4605348.075

0


Here is a fragment of an ASCOM log that I’ve been looking at. I note that the mount is 4.6 arc seconds “off” in DEC per the (red font) third line of this extract. My understanding is the Maxim DL is sending in a correction of 310 milliseconds which would translate out to around 5 arc seconds if one was (and we were) guiding at 1x sidereal. So, at that point it all makes perfect sense. Yet the error is not corrected by the mount (using the timestamp in the first column) until 1.2 seconds later (green font). I keep thinking that I’m interpreting the log incorrectly incorrectly. I can also tell you that a couple of seconds later MDL sends out an even bigger correction and the same thing happens – slow mount response, almost no response from the absolute encoders at all.

If I am reading it correctly, then this must mean that I’m seeing backlash – the motors are running but very little is happeningStill, unless there is a lot of backlash, the correction using the motor encoders should be faster than 1.2 seconds. I can only figure that the code keeps a register with the desired DEC value and keeps the motors turning until it gets there as shown in the green row. Now we had the mount encoders set to ignore at this point, but still I would expect them to move much more than what is shown here as the motors turn. Again, I think that this is another sign that there is a lot of backlash present – those mount encoders don’t lie (☺).

I apologize again if I have completely misinterpreted the ASCOM log. If there’s a document describing it in detail, that would be useful.

Rgrds-Ross

From: SiTechservo@yahoogroups.com [mailto:SiTechservo@yahoogroups.com]
Sent: Thursday, January 18, 2018 11:48 AM
To: russmgenet@aol.com [SiTechservo] <SiTechservo@yahoogroups.com>
Subject: Re: [SiTechservo] Pulse Guiding


It depends on a lot of stuff, the gain you have set in the SiTechExe/Config/ChangeConfig/MountParms (the default is 0.9), your guide rate you've set in ServoConfig, the pulse guide time, motor tuning, if you're in cascade mode, etc.
You can tell yourself. Click on the "Numbers" tab.
Watch the PAxisError and/or SAxisError, and when you have a guide command, you'll see it jump up, then settle down to (hopefully) 00:00:00.0.
Dan


On Thu, Jan 18, 2018 at 8:25 AM, Ross Salinger rgsalinger@hotmail.com<mailto:rgsalinger@hotmail.com> [SiTechservo] <SiTechservo@yahoogroups.com<mailto:SiTechservo@yahoogroups.com>> wrote:

I’d still like to understand “as soon as it can”. Does this mean at the maximum slew speed specified? Does this have something to do with how fast the controller can monitor movement and stop it?
Rgrds-Ross

From: SiTechservo@yahoogroups.com<mailto:SiTechservo@yahoogroups.com> [mailto:SiTechservo@yahoogroups.com<mailto:SiTechservo@yahoogroups.com>]
Sent: Thursday, January 18, 2018 8:10 AM
To: russmgenet@aol.com<mailto:russmgenet@aol.com> [SiTechservo] <SiTechservo@yahoogroups.com<mailto:SiTechservo@yahoogroups.com>>
Subject: Re: [SiTechservo] Pulse Guiding


So according to Dan's post relayed by Dave Lane, using PulseGuide
through ASCOM ignores what ever guide speed is set in
ServoConfig - "It causes the scope to move there as quick as it can". Wow!
Don W
Well, yes and no.
It uses the guide speed to calculate the distance for the move,
After it has a new position, it will move to it as soon as it can.
Usually, this is before the guide time will expire. So, the ASCOM IsGuiding property will say false as soon as the mount is settled, if you have that option checked in SiTechExe/Config/ChangeConfig/ASCOM and Logging.
If this is unchecked, even if the mount is finished getting to the new position, it will still hold the "IsGuiding" as true until the requested guide time has expired.
You'll probably get better guiding with this checked, however, some calibration routines won't calibrate if SiTech says "IsGuiding" is false too soon.
Dan

On Tue, Jan 16, 2018 at 1:52 PM, westergren@netzero.net<mailto:westergren@netzero.net> [SiTechservo] <SiTechservo@yahoogroups.com<mailto:SiTechservo@yahoogroups.com>> wrote:


So according to Dan's post relayed by Dave Lane, using PulseGuide through ASCOM ignores what ever guide speed is set in ServoConfig - "It causes the scope to move there as quick as it can". Wow!

Don W


---In SiTechservo@yahoogroups.com<mailto:SiTechservo@yahoogroups.com>, <dave@davelane.ca<mailto:dave@davelane.ca>> wrote :

To save Dan the trouble, below is what he told me back in October

"But this is how it works. The pulse guide software in SiTechExe calculates the guide rate, and the duration, and turns that into an RA or Dec value to move, and changes the RA or Dec setpoint by that amount. There is an option in the ascom and logging tab where you can check the "isPulseGuiding returns false when settled", so then it will return before the pulse guide duration specified."

The important point is if a Pulse Guide ASCOM command calls, for example, to move 1000 milliseconds West (at guide rate), it doesn't move at guide rate (+sidereal) for 1 second to make the correction. It figures out how far 1000mS at the current guide rate is, changes the RA/Dec target to that value which causes the scope to move there as quick as it can, so guiding corrections typically take less time than expected because the typically slow guide rate is exceeded.
--- Dave

On 2018-01-16 1:02 AM, 'Chuck Shaw' candcshaw@att.net<mailto:candcshaw@att.net> [SiTechservo] wrote:

Ross,



I think Dan should be the one to provide the details of how the guiding commands are structured in Sitechexe.exe. I don’t want to get it wrong for you!!!



Chuck

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