David's Astronomy Pages Notes - Session 743 (2020-01-19)

Notes (S742)

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Notes (S744)

	Session Aims & Highlights
	- Observing Result  - Night Summary Plot  - Session Event Log
	Operational Issues
	- Critical Issues (0),  Major Issues (0),  Minor Issues (4),  Continuous Improvement (3)
	Warm Front
	Investigation:  Telescope Slew Path Issue
	Images from 2020-01-19  >>

Session Aims & Highlights (2020-01-19)

Main aims

1. Targets: Acquire images of selected variable and nearby stars and a few specifically selected deep sky objects

Equipment & Software

• 12" LX200 and ST-10XME
• 80mm APO and ZWO ASI 178MC
• CCDApp2, TheSky6, CCDSoft5, PHD2,  POTH Hub
• Pegasus UPB & Motor Focus, TCF-S
• SharpCap 3.2, PHD2  2.6.6dev3
   
• AstroMain 3.19.7 / 3.19.8 ,  Astroguard 1.2.9,   AstroPlan 1.13.9,  AstroShCap 1.2.10, AstroVOE 1.3.4, UPB 1.4.17  (AstroWeather 1.8.2, AstroAllSky 3.5.1)
  

Highlights

• TPoint Model. TPoint model performing well.   Used Short Mapping Run from preceeding session and this worked well.
  Pointing errors after all slews was < 5' with a few being < 1'.

Lowlights

•   Centering.  Although Slew Errors were small, there were problems in centering several targets.   with some targets taking up to 4 attempts to get from 2-3' error to <1' error.  Balance is too good !.

Summary Plots & Logs

Observing Plan

Observing Result

Dome & Scope Slewing Performance

Slew/Centering Performance

Sky Conditions (Locate Frames)

Night Sky Summary Plot Top axis: Sky Brightness at Zenith (in ADU/s) Lefthand axis: Local Time (hh LT). Righthand axis: Sun Altitude (degs)

Pre-Session Weather Forecast (API data from darksky.net) Forecast showed  85-95% cloud cover clearing around 03:00 with strong winds (20-26 mph) In the event skies were clear the whole night but winds were strong throughout the night, peaking at around 02:00 Conditions were too windy for quality imaging and the observatory was operated for 3 hour period between 21:45 and 00:55 for a TPoint Mapping Run.

Session Event Log

Time     Event Detail 22:47:08 Session Created Live Session Created (2020-01-19 S00743, ImageSaveNum: 743001) 22:47:29   Scope Switched On Telescope Power has been switched on via UPB Powerbox. 22:49:13   Obs.Manager Started Obs.Manager started 22:49:15   Obs.Overseer Started Obs.Overseer started 22:49:20   Services Started Observatory Services started 22:49:50   Camera1 Connected SBIG Camera Connected (set point -25°C) 22:50:21 Observatory (Auto) Observatory placed in Fully-Automated Mode 22:50:25 Session Pending Session pending (2020-01-19) 22:50:27 Session Initiating Session initiating (2020-01-19) 22:50:29   Plan Requested Observing Plan requested from AstroPlan (1.13.10) 22:51:14   Plan Loaded Observing Plan loaded to queue (2020-01-19 V1 BEST PLAN, Plan ID: 458) 22:51:18   Camera1 Connected SBIG Camera Connected (set point -25°C) 22:51:23   Telescope Connected Telescope Connected (TheSky6) 22:51:35 Session Equilibration Session ready for dome & camera equilibration 22:51:37 Wait on Weather Waiting for acceptable weather conditions 22:53:26   Shutter Opened Shutter opened (opening time 45s) 22:53:29   Equilibration Started Dome Equilibration started 22:59:26   Equilibration Ended Dome Equilibration ended (6.0 mins total) 22:59:28 Session Running Session running 22:59:30   Queue Started Observing Queue started (26 targets selected) 23:00:35       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 23:03:17       Focusing Completed Foc1 AutoFocus Completed (Profile No 1) 23:03:20       Focusing Started Foc2 Focusing Started (Secondary Scope, using ShCap) 23:04:53       Focusing Completed Foc2 AutoFocus Completed (Profile No 2) 23:04:56     Target Started (1/26) Target started (1/26, GCVS FO Ori) 23:10:28     Target Completed Target partially completed (1/26, GCVS FO Ori) 23:10:30     Target Started (2/26) Target started (2/26, GCVS FU Ori) 23:12:59       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 23:16:00       Focusing Completed Foc1 AutoFocus Completed (Profile No 3) 23:18:42     Target Completed Target completed (2/26, GCVS FU Ori) 23:18:44     Target Started (3/27) Target started (3/27, PLN 210+ 1.1) 23:21:18       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 23:24:14       Focusing Completed Foc1 AutoFocus Completed (Profile No 4) 23:25:03   SoftSuspend Called Soft Suspend is called due to Deteriorating Conditions (too few stars) 23:34:57     Target Completed Target partially completed (3/27, PLN 210+ 1.1) 23:34:59   Queue Aborted Job Queue aborted 23:35:24   Services Stopped Observatory Services stopped 23:35:28 Program Closed Program closed by User 23:36:14 Session Resumed Live Session Resumed (2020-01-19 S00743, ImageSaveNum: 743027) 23:37:21   Obs.Manager Started Obs.Manager started 23:37:23   Obs.Overseer Started Obs.Overseer started 23:37:27   Services Started Observatory Services started 23:37:49 Observatory (Auto) Observatory placed in Fully-Automated Mode 23:37:53 Session Pending Session pending (2020-01-19) 23:37:55 Session Initiating Session initiating (2020-01-19) 23:37:57   Plan Loaded Observing Plan loaded to queue (2020-01-19 V1 ACTIVE PLAN S743, Plan ID: 458) 23:37:59   Camera1 Connected SBIG Camera Connected (set point -25°C) 23:38:06   Telescope Connected Telescope Connected (TheSky6) 23:38:23 Session Equilibration Session ready for dome & camera equilibration 23:38:26   Equilibration Started Dome Equilibration started 23:38:28   Equilibration Skipped Dome Equilibration skipped by user 23:38:30 Session Running Session running 23:38:32   Queue Started Observing Queue started (24 targets selected) 23:38:34   SoftSuspend Called Soft Suspend is called due to Deteriorating Conditions (too few stars) 23:39:21       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 23:42:11       Focusing Completed Foc1 AutoFocus Completed (Profile No 5) 23:42:14       Focusing Started Foc2 Focusing Started (Secondary Scope, using ShCap) 23:44:45       Focusing Failed Foc2 Focusing Failed - failed QC check (Quadratic) 23:44:47     Target Missed (3/26) Target's time slot was missed (3/26, GCVS SU Tau) 23:44:49     Target Missed (4/26) Target's time slot was missed (4/26, GCVS CN Ori) 23:44:51     Target Missed (5/26) Target's time slot was missed (5/26, GCVS U Gem) 23:44:53     Target Started (6/26) Target started (6/26, GCVS RR Tau) 23:46:27       Focusing Failed Foc1 Focusing Failed - star is too dim (TCF-S) 23:54:19     Target Completed Target completed (6/26, GCVS RR Tau) 23:54:21   Queue Paused Queue paused for SoftSuspend 23:54:23 Session Suspended Session suspended 23:55:10   Shutter Closed Shutter closed (closing time 50s) 00:01:51     Target Cancelled Target cancelled (7/26, GCVS NV Ori) due to cloud 00:14:37     Target Cancelled Target cancelled (8/26, GCVS U And) due to cloud 00:29:37     Target Cancelled Target cancelled (9/26, C/2017 T2 (PanStarrs)) due to cloud 00:38:48     Target Cancelled Target cancelled (10/26, GCVS GK Per) due to other condition 00:47:58     Target Cancelled Target cancelled (11/26, GCVS SY Cnc) due to other condition 00:59:00     Target Cancelled Target cancelled (12/26, GCVS RZ LMi) due to other condition 01:02:02 Session Resuming Session resuming 01:02:47   Shutter Opened Shutter opened (opening time 45s) 01:02:50 Session Running Session running 01:02:52   Queue Resumed Observing Queue resumed 01:02:54     Target Started (13/26) Target started (13/26, GCVS AM CVn) 01:06:17       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 01:09:14       Focusing Completed Foc1 AutoFocus Completed (Profile No 7) 01:12:00     Target Completed Target completed (13/26, GCVS AM CVn) 01:12:02     Target Started (14/26) Target started (14/26, GCVS Z And) 01:15:35       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 01:18:39       Focusing Completed Foc1 AutoFocus Completed (Profile No 8) 01:22:27     Target Completed Target completed (14/26, GCVS Z And) 01:22:30     Target Started (15/26) Target started (15/26, GCVS RX And) 01:25:39       Focusing Failed Foc1 Focusing Failed - star is too dim (TCF-S) 01:29:39     Target Completed Target completed (15/26, GCVS RX And) 01:29:41     Target Started (16/26) Target started (16/26, GCVS DY Per) 01:33:21       Focusing Failed Foc1 Focusing Failed - star is too dim (TCF-S) 01:39:10     Target Completed Target completed (16/26, GCVS DY Per) 01:39:12     Target Started (17/27) Target started (17/27, 3C 58) 01:41:45       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 01:44:35       Focusing Completed Foc1 AutoFocus Completed (Profile No 9) 02:15:52     Target Completed Target completed (17/27, 3C 58) 02:15:54     Target Missed (18/27) Target's time slot was missed (18/27, GCVS CM Tau) 02:15:56     Target Missed (19/27) Target's time slot was missed (19/27, GCVS S Cyg) 02:15:58     Target Started (20/27) Target started (20/27, GCVS GK Per) 02:18:01       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 02:21:08       Focusing Completed Foc1 AutoFocus Completed (Profile No 10) 02:24:07     Target Completed Target completed (20/27, GCVS GK Per) 02:24:09     Target Started (21/27) Target started (21/27, GCVS SY Cnc) 02:27:52       Focusing Failed Foc1 Focusing Failed - star is too dim (TCF-S) 02:32:31     Target Completed Target completed (21/27, GCVS SY Cnc) 02:32:33     Target Started (22/27) Target started (22/27, GCVS RZ LMi) 02:35:13       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 02:38:04       Focusing Completed Foc1 AutoFocus Completed (Profile No 11) 02:43:05     Target Completed Target completed (22/27, GCVS RZ LMi) 02:43:07     Target Started (23/27) Target started (23/27, GCVS AM CVn) 02:46:57       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 02:49:46       Focusing Completed Foc1 AutoFocus Completed (Profile No 12) 02:52:36     Target Completed Target completed (23/27, GCVS AM CVn) 02:52:38     Target Started (24/27) Target started (24/27, GCVS ER UMa) 02:55:14       Focusing Failed Foc1 Focusing Failed - star is too dim (TCF-S) 03:00:09     Target Completed Target completed (24/27, GCVS ER UMa) 03:02:08     Target Started (25/27) Target started (25/27, GCVS R CrB) 03:06:00       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 03:08:35       Focusing Completed Foc1 AutoFocus Completed (Profile No 13) 03:11:28     Target Completed Target completed (25/27, GCVS R CrB) 03:11:30     Target Started (26/27) Target started (26/27, GCVS U Her) 03:14:55       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 03:17:37       Focusing Completed Foc1 AutoFocus Completed (Profile No 14) 03:25:04     Target Completed Target completed (26/27, GCVS U Her) 03:25:06     Target Started (27/27) Target started (27/27, GCVS AM Her) 03:28:49       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 03:31:37       Focusing Completed Foc1 AutoFocus Completed (Profile No 15) 03:36:31     Target Completed Target completed (27/27, GCVS AM Her) 03:36:34   Queue Completed Job Queue completed 03:36:35 Session Continuing Session continuing 03:36:47   Plan Requested Observing Plan requested from AstroPlan (1.13.10) 03:37:11   Plan Loaded Observing Plan loaded to queue (2020-01-19 V2 BEST PLAN, Plan ID: 459) 03:37:47 Session Running Session running 03:37:50   Queue Started Observing Queue started (18 targets selected) 03:42:47     Target Started (1/18) Target started (1/18, GCVS U Gem) 03:45:42       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 03:48:42       Focusing Completed Foc1 AutoFocus Completed (Profile No 16) 03:51:35     Target Completed Target completed (1/18, GCVS U Gem) 03:52:20     Target Started (2/18) Target started (2/18, GCVS SY Cnc) 03:54:17       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 03:57:44       Focusing Completed Foc1 AutoFocus Completed (Profile No 17) 04:00:37     Target Completed Target completed (2/18, GCVS SY Cnc) 04:01:59     Target Started (3/18) Target started (3/18, GCVS RZ LMi) 04:04:28       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 04:07:15       Focusing Completed Foc1 AutoFocus Completed (Profile No 18) 04:12:15     Target Completed Target completed (3/18, GCVS RZ LMi) 04:13:47     Target Started (4/18) Target started (4/18, GCVS ER UMa) 04:16:37       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 04:19:36       Focusing Completed Foc1 AutoFocus Completed (Profile No 19) 04:23:09     Target Completed Target completed (4/18, GCVS ER UMa) 04:24:05     Target Started (5/18) Target started (5/18, GCVS AM CVn) 04:27:20       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 04:30:00       Focusing Completed Foc1 AutoFocus Completed (Profile No 20) 04:32:47     Target Completed Target completed (5/18, GCVS AM CVn) 04:33:38     Target Started (6/18) Target started (6/18, GCVS SS Her) 04:37:07       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 04:40:04       Focusing Completed Foc1 AutoFocus Completed (Profile No 21) 04:43:19     Target Completed Target completed (6/18, GCVS SS Her) 04:43:21     Target Started (7/18) Target started (7/18, GCVS U Her) 04:46:42       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 04:49:24       Focusing Completed Foc1 AutoFocus Completed (Profile No 22) 04:56:53     Target Completed Target completed (7/18, GCVS U Her) 04:56:55     Target Started (8/18) Target started (8/18, GCVS S Cyg) 04:59:52       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 05:02:42       Focusing Completed Foc1 AutoFocus Completed (Profile No 23) 05:12:30     Target Completed Target completed (8/18, GCVS S Cyg) 05:12:32     Target Started (9/18) Target started (9/18, GCVS AM Her) 05:17:04       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 05:20:01   SoftSuspend Called Soft Suspend is called due to Deteriorating Conditions (too few stars) 05:20:04       Focusing Completed Foc1 AutoFocus Completed (Profile No 24) 05:23:50     Target Completed Target partially completed (9/18, GCVS AM Her) 05:23:52   Queue Paused Queue paused for SoftSuspend 05:23:55 Session Suspended Session suspended 05:24:42   Shutter Closed Shutter closed (closing time 49s) 05:27:55     Target Cancelled Target cancelled (10/18, GCVS R CrB) due to cloud 05:33:53   Camera1 SetPoint SBIG Camera Set Point Temperature Updated (new set point -20°C) 05:38:06     Target Cancelled Target cancelled (11/18, GCVS AM Her) due to other condition 05:47:19     Target Cancelled Target cancelled (12/18, GCVS CI Cyg) due to other condition 05:47:29 Session Resuming Session resuming 05:48:14   Shutter Opened Shutter opened (opening time 45s) 05:48:17 Session Running Session running 05:48:19   Queue Resumed Observing Queue resumed 05:48:21     Target Started (13/18) Target started (13/18, GCVS Z And) 05:51:52       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 05:54:51       Focusing Completed Foc1 AutoFocus Completed (Profile No 25) 05:58:38     Target Completed Target completed (13/18, GCVS Z And) 05:58:40     Target Started (14/18) Target started (14/18, GCVS SS Cyg) 06:02:24       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 06:05:21       Focusing Completed Foc1 AutoFocus Completed (Profile No 26) 06:09:00     Target Completed Target completed (14/18, GCVS SS Cyg) 06:11:35     Target Started (15/18) Target started (15/18, GCVS BL Lac) 06:15:21       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 06:18:12       Focusing Completed Foc1 AutoFocus Completed (Profile No 27) 06:21:43     Target Completed Target completed (15/18, GCVS BL Lac) 06:21:53     Target Started (16/18) Target started (16/18, GCVS CY Lyr) 06:24:43       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 06:27:30       Focusing Completed Foc1 AutoFocus Completed (Profile No 28) 06:31:01     Target Completed Target completed (16/18, GCVS CY Lyr) 06:32:11     Target Started (17/18) Target started (17/18, GCVS FG Sge) 06:34:41       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 06:37:31       Focusing Completed Foc1 AutoFocus Completed (Profile No 29) 06:39:59     Target Completed Target completed (17/18, GCVS FG Sge) 06:40:23     Target Started (18/18) Target started (18/18, GCVS V Sge) 06:44:01       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 06:46:58       Focusing Completed Foc1 AutoFocus Completed (Profile No 30) 06:55:17     Target Completed Target completed (18/18, GCVS V Sge) 06:55:20   Queue Completed Job Queue completed 06:55:22 Session Closing Session closing 06:56:15   Shutter Closed Shutter closed (closing time 50s) 06:56:21   Dome Parked Dome parked (parking time 6s) 06:56:34   Telescope Parked Telescope parked (parking time 9s) 06:57:04   Scope Switched Off Telescope Power has been switched off via UPB Powerbox. 06:57:51   Services Stopped Night Services stopped 06:57:53 Session Housekeeping Housekeeping Started (Cleanup FITS, Create Fits Summary, Transfer Files) 06:58:17 Session Finished Session Finished

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Operational Issues (2020-01-19, S743)

• Critical Issues (0)
• Major Issues (0)
• Minor Issues (4)
• Continuous Improvement (3)

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Critical Issues

• None

Major Issues

• None

Minor Issues

• Problem with Focus Temperature Chart Y Axis range changing when restarting AstroMain.  Scale started with 6 to -4C°, but after a program restart the scale changed to 6 to 0°C
  Fixed 2020-01-21 (AstroMain 3.20.0)
   
• CCD cooling unable to keep up with rising temperatures from the passage of a warm front, and eventually maxed out at 100% leading to CCD Temperatures to rise above the setpoint temperature.  Whilst set point temperature was eventually reset to -20° C after a short (20 min) dome closure when session was suspended, the Obs.Manager algorithm should have identified a problem and (gracefully) reset the temperature setpoint when problem arose whilst session was running..   The delay caused multiple raw frames to be acquired at -24.5° C and thus outside nornal tolerance for using standard master darks for -25° C.  Whilst this slight dark frame mismatch was acceptable under the circumstances it caused extra work during image reduction processing post-session.
  Fixed Nov 2020 (AstroMain)
   
• AstroPlan producing plans without deep sky targets even though darkest part of night.  Workaround used in last 3 sessions has been to include specific deep sky targets as ToO targets. Investigating it was found later that Projects marked for use had been reduced to just variable stars at some point (testing on development computer ?) and was preventing deep sky targets (galaxies,nebulae etc) from being included in plans.
  Fixed 2020-01-20 (AstroPlan/Database)
   
• One particular telescope slewing path on the DomeChart appears to slew across the DecLimit area above Dec 66°.  This is merely an artifact caused by limited slew path information leading to interpolation between last valid slew path point and the final destination point. The 'problem' was associated with slew from GCVS AM CVn at Az 96° / Alt 50° to GCVS Z And at Az 334° / Alt 20° where the last point in path is at Az 197.7° / Alt 80.7°. (See Investigation: Telescope Slew Path Issue)
  Fixed 2020-01-23 (AstroMain 3.20.0)

Continuous Improvement

• Rename Focus Profile and guide chart file names to 01, 02, 03 etc, to enable easier viewing / sorting
  Done 2020-01-21 (AstroMain 3.20.0)
   
• Create a new chart type for displaying Zenith FWHM. Add handling to allow realtime upload to website
  Done 2020-01-21 (AstroMain 3.20.0, AstroPlan 1.13.11 & Website)
   
• Add button facility to close(kill) all ACDSee windows
  Done 2020-01-21 (AstroMain 3.20.0 & AstroMove 1.4.2)

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Warm Front

A warm front came through during the session at 02:45 at which time and under clear skies the outside ambient temperature rose by 5°C in 15 minutes (from -0.5°C to 4.5°C).    There was a slight increase in wind speed as warm front came through (from 0-2 mph  to 4-6 mph). The passage of the warm front had consequences on CCD Temperature regulation and on Seeing.

[ Although there was nothing remarkable about the sunset skies at my observatory site, other locations in Scotland were treated to a vivid display of colours at sunset - see BBC report https://www.bbc.co.uk/news/uk-scotland-51174308 ]

Night Summary Plot 01:00 to 05:00 Warm front comes through at 02:45 under clear skies. Slight increase in wind

Temperature Data (small bug with temperature axis scaling following program restart at 23:30 needs to be fixed)

CCD Temperature Regulation CCD Camera Cooling responds to the warm front by raising cooling power from 73% to 82% whilst maintaining  the camera's CCD Temperature at it's set point of -25°C At around 04:30 and probably related to rising temperatures inside the dome the camera cooling power maxed out at 100% and the CCD rose to -24.5°C. After a short (20min) dome closure the CCD's Setpoint Temperature is automatically reduced to -20°C and cooling power drops back to a comfortable 70% level. (Obs.Manager's algorithm should be changed so that it can recognised a loss of control like the one at 04:30 and responded by gracefully lowering the setpoint, process takes around 3 minutes )

Seeing / Zenith FWHM Zenith FWHM as determined by measuring Focus Profile and extrapolating to zenith

Focus Profiles at 01:15  & 02:34 (before warm front), compared with profiles at 03:28 & 04:04 (after warm front) The two profiles before warm front show zenith FWHM of 5.93 and 5.39" whilst the two profiles after passage of the warm front show much better zenith FWHM of 2.81 and 2.79"

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Investigation:  Telescope Slew Path Issue

One particular telescope slewing path on the DomeChart appears to slew across the DecLimit area above Dec 66° (see chart below).  This is merely an artifact caused by limited slew path information leading to interpolation between last valid slew path point and the final destination point. The 'problem' was associated with slew from GCVS AM CVn at Az 96° / Alt 50° to GCVS Z And at Az 334° / Alt 20° where the last point in path is at Az 197.7° / Alt 80.7°.

Examination of the log file (see below) indicates that scope slew starting at 01:12:03 but didn't show any significant scope movement to 01:12:09. The log file suggests that scope slew had finished after 17s (ie 01:12:30), but the scope position suggests that scope hadn't reached destination at this time. Its possible that the scope slew time is correct but the scope coordinates that are read from POTH.Telescope lag behind the scope's actual position by some 6 secs, or the end of slew is recorded prematurely.   Prehaps the scope path should continue recording for 6s beyond the indication point used to signify the end of the slew ?


01:12:02.12 | GCVS Z And PreSlew ScopeAzimuth Info | Scope Azimuth Before Slew 95.7
01:12:02.12 | GCVS Z And PreSlew ScopeAltitude Info | Scope Altitude Before Slew 49.6

01:12:02.21 | GCVS Z And SlewTo Ra Info | Slew Ra 23 34 01.184 (CurrentEpoch
01:12:02.21 | GCVS Z And SlewTo Dec Info | Slew Dec +48 53 59.58 (CurrentEpoch
01:12:02.21 | GCVS Z And Set Telescope Ok | Setting Telescope.Asynchronous = 1

01:12:03.15 | GCVS Z And ScopePath Info | 01:12:03 Az: 95.74, Alt: 49.56, CummAngle: 0.000
01:12:03.94 | GCVS Z And ScopePath Info | 01:12:03 Az: 95.74, Alt: 49.56, CummAngle: 0.001
01:12:04.66 | GCVS Z And ScopePath Info | 01:12:04 Az: 95.74, Alt: 49.56, CummAngle: 0.001
01:12:05.33 | GCVS Z And ScopePath Info | 01:12:05 Az: 95.74, Alt: 49.56, CummAngle: 0.001
01:12:05.72 | GCVS Z And ScopePath Info | 01:12:05 Az: 95.74, Alt: 49.56, CummAngle: 0.001
01:12:06.11 | GCVS Z And ScopePath Info | 01:12:06 Az: 95.74, Alt: 49.56, CummAngle: 0.001
01:12:06.50 | GCVS Z And ScopePath Info | 01:12:06 Az: 95.74, Alt: 49.56, CummAngle: 0.001
01:12:06.89 | GCVS Z And ScopePath Info | 01:12:06 Az: 95.74, Alt: 49.56, CummAngle: 0.001
01:12:09.29 | GCVS Z And ScopePath Info | 01:12:09 Az: 93.42, Alt: 59.87, CummAngle: 0.001
01:12:10.81 | GCVS Z And ScopePath Info | 01:12:10 Az: 97.00, Alt: 62.49, CummAngle: 13.650
01:12:11.90 | GCVS Z And ScopePath Info | 01:12:11 Az: 101.12, Alt: 70.04, CummAngle: 16.662
01:12:13.35 | GCVS Z And ScopePath Info | 01:12:13 Az: 101.45, Alt: 69.96, CummAngle: 22.327
01:12:15.20 | GCVS Z And ScopePath Info | 01:12:15 Az: 115.57, Alt: 77.08, CummAngle: 59.556
01:12:15.91 | GCVS Z And ScopePath Info | 01:12:15 Az: 126.48, Alt: 77.00, CummAngle: 104.227
01:12:16.83 | GCVS Z And ScopePath Info | 01:12:16 Az: 140.01, Alt: 79.03, CummAngle: 106.969
01:12:17.69 | GCVS Z And ScopePath Info | 01:12:17 Az: 156.72, Alt: 80.43, CummAngle: 109.714
01:12:19.23 | GCVS Z And ScopePath Info | 01:12:19 Az: 197.73, Alt: 80.70, CummAngle: 109.714
 
01:13:06.38 | GCVS Z And SlewToRaDec Overall (1)Info | Overall Slew Time : 63.3s
01:13:06.38 | GCVS Z And SlewToRaDec Scope Info | Scope Slew Time : 17.0s
01:13:06.38 | GCVS Z And SlewToRaDec Dome Info | Dome Slew Time : 63.6s
01:13:06.38 | GCVS Z And Set Telescope Ok | Setting Telescope.Asynchronous = 0
01:13:06.38 | GCVS Z And Total ScopePath Info | 01:13:06 Total Angle Change: 109.714, New SlewAngle : 207.127
 
01:13:06.52 | GCVS Z And Continue Ok | IamAlive: SlewToTargetRaDec
01:13:06.52 | GCVS Z And Get ScopeSlewSpeed Info | Scope Speed: 12.2 deg/sec (207.1 degs, 17s)
01:13:06.52 | GCVS Z And Session.Slew Info | Starting SaveSlewFileToLiveFolder


Discussion
Code review shows that end of slew is indicated when the 'AngularChange' between successive points falls to < 0.1 arc min (i.e. < 6 arc secs).
The last two points both have a CummAngle of 109.714 indicating an apparent angular change of 0.0 arc min, but their Az Alt positions clearly haven't stabilised, so there is a bug somewhere !

Angular change between two successive points is given by the equation
    AngularChange = AngularSeparation(LastRa, LastDec, RightAscension, Declination)

Logs can rule out a problem caused by AngularSeparation routine producing a non-number result which would have otherwise caused 'CummulativeAngular Change' to momentarily stop increasing.  Therefore it is almost certain that the Scope.RightAscension and Scope.Declination on one read cycle must have given the same values as the preceeding (Last) cycle.    This could occur if values are read less than 0.2s apart  (designed to limit overcommunication with POTH / Scope) or have produced exceptions twice in a row (giving vcNull -99 values both times and thus a zero AngularChange & no increase in 'CummulativeAngularChange')

The read cycle has a 0.25s thread sleep in it and therefore reading of Scope RA/Dec can not be less than 0.2s apart.  Log times support this and suggest the read points occur between 0.4s and 2.4s apart.  (average 1.0s).

Note: the 'Telescope.IsSlewComplete' function can not be used to indicate when telescope has finished slewing as it only goes to true when both the scope and the slaved dome have finished slewing.

Conclusions
It can probably be assumed that due to overload on the POTH process, LX200 driver or LX200 Autostar II that a new telescope position hasn't been available and the previously available position has been given or a Null value returned, leading to a calculation of zero apparent movement of the scope between two successive read cycles.

Fixes
Changes have been made to the 'Scope.SlewTheSkyScopeToRaDec' routine in AstroMain 3.20 in an attempt to resolve the issue.

• if an exception occurs in Scope.GetRaDec this is is logged in the logfile (to help diagnosis)
• if Null Ra / Dec values are returned by Scope.GetRaDec (via calls to the Scope.RightAscension & Scope.Declination properties) the values are re-read after a short delay (0.125 s).
• where movement between successive points is <1' this is highlighted in the slew path record in the log file.
• a 'zero' or 'near zero' Angular Change (Angular Change < 0.1 arc min) is only used to indicate the end of the telescope slew if the distance to the planned destination is < 1 arc deg, or if the scope has become stationary (semi-stationary) for more than 4s.  
  (1 arc deg is used as there will be differences between the Poth.Scope Position and the TheSky6.Scope position due to TPoint modelling.)
•  Thread.sleep time is varied in order to try to maintain a read cycle time of 0.4s.
  (a cycle currently taking 0.40s will still take 0.40s but a cycle that currently takes 2.40s will take only 2.15s.)
  

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