David's Astronomy Pages Notes - Session 720 (2019-11-08)

Notes (S719)

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Notes (S721)

	Session Aims & Highlights
	- Observing Result  - Night Summary Plot  - Session Event Log
	Operational Issues
	- Critical Issues (0),  Major Issues (3),  Minor Issues (3),  Continuous Improvement (3)
	Secondary Scope - Focusing Issue
	Images from 2019-11-08  >>
	2019-11-11
	Secondary Scope - Focusing Backlash
	Secondary Scope - Focusing using SharpCap Focus Measurements
	2019-11-12
	Secondary Scope - Focusing with New Backlash Compensation

Session Aims & Highlights (2019-11-08)

Main aims

1. Smarter Suspension:  Test bug fixes to new code that suspends session if 'AllSkyStars' count falls below 20
2. Targets: Acquire images of a selection of new targets plus monitoring of previous variable stars, nearby stars and comets.
   (Rain and/or cloud was expected to interrupt or possibly end the session at some point)
   

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
   
• AstroMain 3.17.4 ,  Astroguard 1.2.8,   AstroPlan 1.13,  AstroShCap 1.2.6, AstroVOE 1.3.4, UPB 1.4.17  (AstroWeather 1.7.9, AstroAllSky 3.5)

Highlights

• Smarter Suspension. New version of AstroMain worked really well and the Observatory/Software responded well to changing cloud conditions, taking advantage of clearer intervals and suspending operatures (including closing the shutter) when the conditions were not worth observing (images would be poor or completely cloud out). .This success is important step in optimising the observatory operations since knocking out non-useful data speeds up the whole process of data transfer, data reduction and analysis. It also saves wear and tear to equipment.  Key to this improvement has been the use of the star count from AllSky Camera which provide a better discremination of marginal conditions that the Clarity reading from the Cloud Sensor.   The latter is still used for recognising potential rain clouds.

Lowlights

• User Errors.    Errors at start of session, which unnecessarily led to the whole Observing Software Suite to have to be restarted and a further user errors after the session which didn't switch off the power in the morning and reset the observatort mode, which saw the Observatory automatically startup just after sunset the following evening, and then a error which saw the telescope powered down without parking it will will create issues  and extra user interventation at the start of the next session.

Summary Plots & Logs

Observing Plan

Observing Result

Slew/Centering Performance

Dome Slewing 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 some initial clear patches, but with cloud progressively developing through the night, but otherwise dry and calm In the event there was a moderately clear interval between 18:30 and 22:30, with another clear interval at 02:30-03:45.  Transparency wasn't great at any stage. Operations didn't start till suspended at 21:50 and took advantage of clear intervals, suspending when sky deteriorated.

Session Event Log

Time     Event Detail 17:17:16 Session Created Live Session Created (2019-11-08 S00720, ImageSaveNum: 720001) 17:17:52   Obs.Manager Started Obs.Manager started 17:17:54   Obs.Overseer Started Obs.Overseer started 17:17:58   Services Started Observatory Services started 17:18:24   Scope Switched On Scope Power has been switched on via UPB Powerbox. 17:20:08   Services Started Observatory Services started 17:26:03 Observatory (Auto) Observatory placed in Fully-Automated Mode 17:26:09 Session Pending Session pending (2019-11-08) 17:26:11 Session Initiating Session initiating (2019-11-08) 17:26:13   Plan Requested Observing Plan requested from AstroPlan (1.13) 17:27:29   Plan Loaded Observing Plan loaded to queue (2019-11-08 V1 BEST PLAN, Plan ID: 417) 17:27:42   Camera1 Connected SBIG Camera Connected (set point -20°C) 17:27:47   Telescope Connected Telescope Connected (TheSky6) 17:28:00 Session Equilibration Session ready for dome & camera equilibration 17:28:02 Wait on Weather Waiting for acceptable weather conditions 17:33:02 Session Suspended Session suspended 17:33:04   Shutter Closed Shutter already closed (closed at 05:00, closing time 49s) 17:33:06   Queue Started Observing Queue started (29 targets selected) 17:33:08     Target Missed (1/29) Target's time slot was missed (1/29, GCVS Z And) 17:45:36     Target Cancelled Target cancelled (2/29, 68P/Klemola) due to other condition 17:53:32     Target Cancelled Target cancelled (3/29, GCVS FG Sge) due to cloud 18:02:30     Target Cancelled Target cancelled (4/29, GCVS CY Lyr) due to cloud 18:08:59 Session Resuming Session resuming 18:09:45   Shutter Opened Shutter opened (opening time 45s) 18:09:48 Session Running Session running 18:09:50   Queue Resumed Observing Queue resumed 18:09:52     Target Started (5/29) Target started (5/29, 61 Cyg) 18:13:25     Target Completed Target completed (5/29, 61 Cyg) 18:13:28     Target Started (6/29) Target started (6/29, GCVS CI Cyg) 18:15:25       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 18:17:15       Focusing Completed Foc1 AutoFocus Completed (Profile No 1) 18:20:51     Target Completed Target completed (6/29, GCVS CI Cyg) 18:20:53     Target Started (7/29) Target started (7/29, GCVS S Cyg) 18:23:05       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 18:24:55       Focusing Completed Foc1 AutoFocus Completed (Profile No 2) 18:35:07     Target Completed Target completed (7/29, GCVS S Cyg) 18:35:09     Target Started (8/29) Target started (8/29, IC 5067). Using SharpCap 18:46:35     Target Completed Target completed (8/29, IC 5067) 18:49:28     Target Started (9/29) Target started (9/29, GCVS HH And) 18:52:30       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 18:54:25       Focusing Completed Foc1 AutoFocus Completed (Profile No 3) 18:55:59     Target Completed Target completed (9/29, GCVS HH And) 18:56:53     Target Started (10/29) Target started (10/29, GCVS BL Lac) 18:59:07       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 19:01:03       Focusing Completed Foc1 AutoFocus Completed (Profile No 4) 19:05:28     Target Completed Target completed (10/29, GCVS BL Lac) 19:06:41     Target Started (11/29) Target started (11/29, GCVS TT Ari) 19:10:26       Focusing Failed Foc1 Focusing Failed - star is too dim (TCF-S) 19:17:24     Target Completed Target completed (11/29, GCVS TT Ari) 19:18:07     Target Started (12/29) Target started (12/29, GCVS RX And) 19:21:24       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 19:23:15       Focusing Completed Foc1 AutoFocus Completed (Profile No 5) 19:23:44       Focusing Started Foc2 Focusing Started (Secondary Scope) 19:25:54       Focusing Completed Foc2 AutoFocus Completed (Profile No 6) 19:28:34     Target Completed Target completed (12/29, GCVS RX And) 19:28:36     Target Started (13/29) Target started (13/29, GCVS U And) 19:31:26       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 19:33:14       Focusing Completed Foc1 AutoFocus Completed (Profile No 7) 19:33:57       Focusing Started Foc2 Focusing Started (Secondary Scope) 19:36:28       Focusing Failed Foc2 Focusing Failed - failed QC check (Quadratic) 19:44:22     Target Completed Target partially completed (13/29, GCVS U And) 19:44:24     Target Started (14/29) Target started (14/29, GCVS DY Per) 19:53:13     Target Completed Target partially completed (14/29, GCVS DY Per) 19:53:15     Target Started (15/29) Target started (15/29, GCVS AM Her) 19:56:11       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 19:58:14       Focusing Completed Foc1 AutoFocus Completed (Profile No 9) 20:02:51     Target Completed Target partially completed (15/29, GCVS AM Her) 20:02:53     Target Started (16/29) Target started (16/29, GCVS S Cyg) 20:05:08       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 20:07:00       Focusing Completed Foc1 AutoFocus Completed (Profile No 10) 20:17:20     Target Completed Target completed (16/29, GCVS S Cyg) 20:17:22     Target Started (17/29) Target started (17/29, GCVS SS Cyg) 20:24:51     Target Completed Target completed (17/29, GCVS SS Cyg) 20:27:22     Target Started (18/29) Target started (18/29, GCVS SS Cyg) 20:28:03       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 20:30:04       Focusing Completed Foc1 AutoFocus Completed (Profile No 11) 20:33:46     Target Completed Target completed (18/29, GCVS SS Cyg) 20:41:44     Target Started (19/29) Target started (19/29, C/2017 T2 (PanStarrs)) 20:45:20       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 20:47:09       Focusing Completed Foc1 AutoFocus Completed (Profile No 12) 20:55:34     Target Completed Target completed (19/29, C/2017 T2 (PanStarrs)) 20:55:36     Target Started (20/29) Target started (20/29, C/2018 N2 (ASASSN)) 20:57:52       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 21:00:09       Focusing Completed Foc1 AutoFocus Completed (Profile No 13) 21:00:41       Focusing Started Foc2 Focusing Started (Secondary Scope) 21:03:14       Focusing Failed Foc2 Focusing Failed - failed QC check (Range) 21:11:50     Target Completed Target completed (20/29, C/2018 N2 (ASASSN)) 21:11:52     Target Started (21/29) Target started (21/29, GSC 1224:29) 21:14:25 Critical RainThreat Alert Critical Rain Threat Alert (Obs.Manager will close the Shutter) 21:14:27   HardSuspend Called Hard Suspend is called due to Critical Conditions (threat of rain) 21:14:29     Target Aborted (21/29) Target aborted (21/29, GSC 1224:29) due to threat of rain 21:14:31   Queue Paused Queue pausing for HardSuspend 21:14:33 Session Suspended Session suspended 21:15:20   Shutter Closed Shutter closed (closing time 49s) 21:18:56     Target Cancelled Target cancelled (21/29, GSC 1224:29) due to cloud 21:24:31   Camera1 SetPoint SBIG Camera Set Point Temperature Updated (new set point -25°C) 21:37:36     Target Cancelled Target cancelled (22/29, GCVS CM Tau) due to cloud 21:47:12     Target Cancelled Target cancelled (23/29, GCVS SU Tau) due to cloud 21:57:31     Target Cancelled Target cancelled (24/29, GCVS RR Tau) due to cloud 22:07:04     Target Cancelled Target cancelled (25/29, GCVS ER UMa) due to cloud 22:15:25     Target Cancelled Target cancelled (26/29, GCVS FU Ori) due to other condition 22:22:54     Target Cancelled Target cancelled (27/29, WDS GRB 34) due to other condition 22:30:35     Target Cancelled Target cancelled (28/29, GCVS GK Per) due to cloud 22:44:18 Session Resuming Session resuming 22:45:04   Shutter Opened Shutter opened (opening time 46s) 22:45:07 Session Running Session running 22:45:09   Queue Resumed Observing Queue resumed 22:45:11     Target Started (29/29) Target started (29/29, GCVS FO Ori) 22:51:30     Target Completed Target completed (29/29, GCVS FO Ori) 22:51:33   Queue Completed Job Queue completed 22:51:34 Session Continuing Session continuing 22:51:46   Plan Requested Observing Plan requested from AstroPlan (1.13) 22:52:02   Plan Loaded Observing Plan loaded to queue (2019-11-08 V2 BEST PLAN, Plan ID: 418) 22:52:04 Session Running Session running 22:52:06   Queue Started Observing Queue started (34 targets selected) 22:54:46     Target Started (1/34) Target started (1/34, GCVS BL Lac) 22:57:53       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 22:59:40       Focusing Completed Foc1 AutoFocus Completed (Profile No 15) 23:04:01     Target Completed Target completed (1/34, GCVS BL Lac) 23:04:34     Target Started (2/34) Target started (2/34, GCVS HH And) 23:07:13       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 23:09:06       Focusing Completed Foc1 AutoFocus Completed (Profile No 16) 23:10:44     Target Completed Target completed (2/34, GCVS HH And) 23:11:59     Target Started (3/34) Target started (3/34, GCVS TT Ari) 23:15:12       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 23:17:23       Focusing Completed Foc1 AutoFocus Completed (Profile No 17) 23:24:01     Target Completed Target completed (3/34, GCVS TT Ari) 23:24:03     Target Started (4/34) Target started (4/34, GCVS Z And) 23:27:16       Focusing Started-Foc1 Foc1 Focusing Started (TCF-S) 23:29:10       Focusing Completed Foc1 AutoFocus Completed (Profile No 18) 23:32:59     Target Completed Target completed (4/34, GCVS Z And) 23:33:01     Target Started (5/34) Target started (5/34, GCVS RX And) 23:40:31   Telescope Disconnected Telescope Disconected (TheSky6) 23:40:35   Telescope Connected Telescope Connected (TheSky6) 23:44:01     Target Completed Target partially completed (5/34, GCVS RX And) 23:44:03     Target Started (6/34) Target started (6/34, GSC 1224:29) 23:44:09     Target Failed Target failed due to slew error (6/34, GSC 1224:29) 23:48:46     Target Started (7/34) Target started (7/34, GCVS GK Per) 23:48:54     Target Failed Target failed due to slew error (7/34, GCVS GK Per) 23:56:37     Target Started (8/34) Target started (8/34, GCVS DY Per) 23:56:44     Target Failed Target failed due to slew error (8/34, GCVS DY Per) 00:05:55     Target Started (9/34) Target started (9/34, 61 Cyg) 00:06:03     Target Failed Target failed due to slew error (9/34, 61 Cyg) 00:12:59     Target Started (10/34) Target started (10/34, GCVS SS Cyg) 00:13:06     Target Failed Target failed due to slew error (10/34, GCVS SS Cyg) 00:23:41   SoftSuspend Called Soft Suspend is called due to Deteriorating Conditions (too few stars) 00:27:20     Target Started (11/34) Target started (11/34, C/2018 N2 (ASASSN)) 00:27:28     Target Failed Target failed due to slew error (11/34, C/2018 N2 (ASASSN)) 00:27:30   Queue Paused Queue paused for SoftSuspend 00:27:33 Session Suspended Session suspended 00:28:21   Shutter Closed Shutter closed (closing time 49s) 00:38:12 Session Resuming Session resuming 00:38:57   Shutter Opened Shutter opened (opening time 45s) 00:38:59 Session Running Session running 00:39:01   Queue Resumed Observing Queue resumed 00:41:05     Target Started (12/34) Target started (12/34, GCVS FO Ori) 00:41:13     Target Failed Target failed due to slew error (12/34, GCVS FO Ori) 00:47:54   SoftSuspend Called Soft Suspend is called due to Deteriorating Conditions (too few stars) 00:49:13     Target Started (13/34) Target started (13/34, GCVS FU Ori) 00:49:20     Target Failed Target failed due to slew error (13/34, GCVS FU Ori) 00:49:22   Queue Paused Queue paused for SoftSuspend 00:49:24 Session Suspended Session suspended 00:50:13   Shutter Closed Shutter closed (closing time 49s) 01:15:13     Target Cancelled Target cancelled (14/34, GCVS CM Tau) due to other condition 01:16:36 Session Resuming Session resuming 01:17:21   Shutter Opened Shutter opened (opening time 45s) 01:17:24 Session Running Session running 01:17:26   Queue Resumed Observing Queue resumed 01:17:28     Target Started (15/34) Target started (15/34, GCVS RR Tau) 01:17:30     Target Failed Target failed due to slew error (15/34, GCVS RR Tau) 01:26:47     Target Started (16/34) Target started (16/34, GCVS CN Ori) 01:26:54     Target Failed Target failed due to slew error (16/34, GCVS CN Ori) 01:35:08     Target Started (17/34) Target started (17/34, GCVS SY Cnc) 01:35:16     Target Failed Target failed due to slew error (17/34, GCVS SY Cnc) 01:44:17     Target Started (18/34) Target started (18/34, GCVS RZ LMi) 01:44:27     Target Failed Target failed due to slew error (18/34, GCVS RZ LMi) 01:54:54   SoftSuspend Called Soft Suspend is called due to Deteriorating Conditions (too few stars) 01:55:35     Target Started (19/34) Target started (19/34, GCVS U Gem) 01:55:42     Target Failed Target failed due to slew error (19/34, GCVS U Gem) 01:55:44   Queue Paused Queue paused for SoftSuspend 01:55:46 Session Suspended Session suspended 01:56:34   Shutter Closed Shutter closed (closing time 49s) 02:11:58     Target Cancelled Target cancelled (20/34, WDS GRB 34) due to cloud 02:24:10     Target Cancelled Target cancelled (21/34, GCVS U And) due to cloud 02:38:39     Target Cancelled Target cancelled (22/34, C/2017 T2 (PanStarrs)) due to cloud 02:48:00     Target Cancelled Target cancelled (23/34, GCVS SU Tau) due to cloud 03:07:26     Target Cancelled Target cancelled (24/34, Scholz's Star) due to cloud 03:18:02     Target Cancelled Target cancelled (25/34, LAMOST-HVS1) due to cloud 03:49:22     Target Cancelled Target cancelled (26/34, C/2019 Q4 (Borisov)) due to cloud 04:11:15     Target Cancelled Target cancelled (27/34, NGC 3365) due to cloud 04:26:16     Target Cancelled Target cancelled (28/34, GCVS CN Leo) due to cloud 04:45:28     Target Cancelled Target cancelled (29/34, UGC 4596) due to cloud 05:07:20     Target Cancelled Target cancelled (30/34, NGC 3454) due to cloud 05:29:12     Target Cancelled Target cancelled (31/34, NGC 3455) due to cloud 05:51:04     Target Cancelled Target cancelled (32/34, SHK 1) due to cloud 06:03:40     Target Cancelled Target cancelled (33/34, 38P/Stephan-Oterma) due to cloud 06:23:52     Target Cancelled Target cancelled (34/34, GCVS DX Cnc) due to cloud 06:23:57   Queue Completed Job Queue completed 06:24:04 Session Closing Session closing 06:24:09   Shutter Closed Shutter already closed (closed at 01:56, closing time 49s) 06:25:09   Dome Parked Dome parked (parking time 60s) 06:25:20   Telescope Parked Telescope parked (parking time 11s) 06:26:04 Session Housekeeping Housekeeping Started (Cleanup FITS, Create Fits Summary, Transfer Files) 06:26:18 Session Finished Session Finished

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Operational Issues (2019-11-08, S720)

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

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Critical Issues

• None

Major Issues

• New feature recording and plotting path of Scope Slew produces several anomlous path results with slew around N (Az 0 / 360 deg) position.  The observatory was visited on the first occasion (TT Ari) just to confirm that the scope and lead was ok.  SlewTable showed that the scope was taking an apparently very long route to the target (eg.  288.2 deg) and achieving this is 24s, producing an impossibly fast slew time of 12 deg/sec. 
  Fixed (AstroMain 3.17.5)
   
• After Jog operations hung at 23:34:41 on Run 2 Target Target 5/34  (RX And) and the Obs.Overseer process intervened to kick start the job queue (which it did), TheSky was left in a manner that produced errors when trying to access telescope operations and xx target failed.
  Although logged as a major issue, the position is an improvement on early incidents where the Job Queue remained completely frozen.
  The Obs.Manager remained in control, closing the dome shutter when skies went cloudy and parked the telescope ok at the end of the session   (Need to check if telescope tracking was stopped when skies went cloudy later on, need to check that scope is in correct parked position).  Closed following review in 2021 (new Jog routines added in 2Q 2021).
  Closed 2021-05-10 (AstroMain)
   
• Automated Focusing of Secondary Scope isn't achieving desired results.  PHD2 looping/guiding working and HFD are being collected. Focuser is being moved to required step positions and HFD values are being collected from PHD2 from the locked 'Guide Star', however the profile is very flat, and the no proper focus point is visible.  Partly an issue of PHD2 locking onto a 'non-star' na dpartly due to a focuser backlash issue.   As moving the focuser to different positions manually results in focus point shifting by 500+.  Daytime Investigations shows that the backlash is in the order of 1500 steps (vs.  40000 step range for the motor focus).  This is far bigger than the backlash compensation being previously used (400) and bigger than the compensation value (800) being experimented with during the session. Backlash compensation value of 1800 will be used. (with Direction In). Improvements also made to Focus Profile routines for Focuser2  and with options to use either SharpCap or PHD2.
  Fixed  2019-11-18 (Observatory, AstroMain 3.17.8)

Minor Issues

• RX And Focus Profile Tab contain bad row with FWHM -99, HFD = 0.0 and SN  63095734448019500000 .     This occured on step 9/14.  The FWHM/HFD values are tolerable provided that point was rejected for making the quadratic fit, but the very large SN is not acceptable.  This is the first time this error has been seen.
  Fixed (AstroMain 3.17.5)
   
• SlewTheSkyScopeToRaDec task for one target (DY Per) took an unexpectedly long time.  Slew to target 14/29 ( DY Per) took unusually long time (360s).  In fact the routine only exited the slew loop when it reached a 6 minute timeout check. Examining log files showed that the Dome Slew took 24s, whilst the Scope Slew was effectively completed after some 16s or so.   The problem was caused by a rouge result from the first call to AngularSeparation() function which gave a NaN result.    This result carried through to the SumAngularChange  variable   (SumAngularChange = SumAngularChange + AngularChange) which could never escape from the NaN value, which prevented a particular finish criteria (SumAngularChange > 0.2) from ever being True.   Routine modified to check that AngularSeparation is Not NaN before trying to use it.
  Fixed (AstroMain 3.17.5)
   
• Slight bug with drawing DecLimit on Slew Chart (diagonal line produced across the drawn circle. This seems to be simply a rogue result. Debug code added to list data used when line segment is > 4
  Fixed 2020 (AstroMain)

Continuous Improvement

• Report Messages are producing too much white space above the line 'Adjust Focus' . One blank line needs to be removed
  Fixed (AstroMain 3.17.5)
   
• Check out the ASCOM property Telescope.UTCDate as a possible useful logging /diagnostic tool.   
  (Also check Telescope.SlewSettleTime, Telescope.GuideRateRightAscension,  Telescope.CanSetGuideRates   New code added in 2Q 2021 to compare telescope UTC time with computer UTC time following telescope connection
  Closed 2021-05-10 (AstroMain)
   
• SharpCap target IC 5067 took 50 x 10s frames, but only 1 frame was stacked, 49 frames were dropped. Sky was clear (check this)and the 1 stacked frame looked ok.  It is suspected that frames might of been rejected as the FWHM values were too high (focus issue) or sky was too bright (bright moonlit sky)
  >>To be checked (SharpCap / AstroShCap)

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Secondary Scope - Focusing Issue

Although a motor focus was installed on the guidescope/secondary scope in Nov 2018 (Installation Notes 2018-11-07), using it to focus the scope and in particular using it to fully automate the focusing of the scope has proven to rather challenging.  Trying to focus using images/and HFD values from PHD2 proved difficult and swapping to and fro with SharpCap was difficult.  Attempts to use CCDSoft to collect focus star image from ASI ZWO camera on the secondary scope whilst it worked in test environment but in practice it resulted in instablity in my telescope/camera control software which I was unable to quickly overcome. 

However in late 2019 I'm having another bash at finding a solution to the issue of focusing the guidescope/secondary scope.

•  I have a self-built client module for operating the Pegasus Astro Motor Focus using the UPB's ASCOM focuser driver
   
•  The latest version of PHD2 now provides a means of directly accessing the HFD value of PHD2's guide star via PHD2 OpenGuding Server.
    
•  There are also increased focusing capabilities in SharpCap which can be potentially accessed via the server interface that I've built (AstroShCap).
   
•  I can build upon the Focus Profiling method I use for focusing my Main Scope using TCF-S Focuser
  
  (this is where the routine selects a focuser step range centered on the current focus position and then moves the focuser out to a position beyond the intended range by an amount greater than the backlash, and then moves back in to the start of the focus range, and then steps in across the range at regular step increments taking focus measurements at each step, from which position of best focus can be computed )

Example of Automated Focus Profile taken on Main Scope Orange dots are FWHM measurements made with CCDSoft Blue dots are HFD measurements calculated from the CCDSoft image Yellow curve is best-fit quadratic equation that leads to best focus position Profile has a good shape there is high confidence in the auto-calculated position of best focus position

Attempts to automate the focusing process using PHD2 ran into some difficulties
-  PHD2 isn't very good at finding / locking onto a star when it is out of focus, due to starmass changes and
   difficulty distinguishing hot patches of pixels from stars
-  HFD values would often stay flat for relatively large changes in focuser position when running a focus profile even though profiles centered on
a starting position of reasonably focus

Example of Automated Focus Profile taken on Secondary Scope, 2019-11-08 Using Backlash Compensation of 400. Blue dots are HFD measurements from PHD2 Profiles are flat without any peak focus even though profiles centered on a position of reasonably focus  (~ HFD 5.5 - 6)

Example of Automated Focus Profile taken on Secondary Scope, 2019-11-09 Using Backlash Compensation of 800

Suspecting that there might be an issue with the amount of combined backlash on the motor focus/rack & pinion focuser the backlash compensation was increased from 400 steps to 800 steps to see if this might resolve the issue. Although it didn't resolve it did prompt me into doing some more testing in the following days

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2019-11-11

Secondary Scope - Focusing Backlash

Having suspected that there might be an issue with insufficient compensation of backlash a daytime test was carried out in which having driven the focus motors in one direction to the point in which the focuser in moving, the focus motors were reversed and a careful watch made for the point at which the focuser then began to move in the opposite direction.   This was most easily done by spotting the point at which the fine focus knob began to turn and seeing how steps the motor focuser had changed by.  Although this doesn't necessarily include the backlash associated with the rack and pinion focuser on the scope it does evidently show the bulk of the backlash in my system.  

Surprisingly this backlash amounts to some 1500 steps, equivalent to about 2.7mm of take-up (based on my focus tube travel of 0.0018mm per step). This is also equivalent to a 1/4 turn of the coarse focus knob (based on 0.06 deg per step), or 2.5 turns of the 1:10 fine focus knob.

With this measurement I entered a backlash compensation value of 1800 step into my motor focus settings, pending a more detailed measurement in the next observatory session (either a live or test session).

The precise origin of this large backlash is uncertain.  A large backlash was noticed during original manual focusing prior to the fitting of the motor focus, and was not expected from the Pegasus Universal Motor Focus Unit (PEG-MF3-MOTOR-UN) which was meant to have a "gearbox with very low backlash".  Prehaps something became loose during the installation ?

Unfortunately I don't have a record or any recollection of why I had chosen the original value of 400 for backlash compensation. WIthout this I can't  understand whether the backlash has always been as high as 1500 steps or has gradually or suddenly increased..

[ This daytime backlash estimation was done as part of setting up for transit of Mercury however lack of prior preparation on my part and then cloud prevented Transit observation. Got as far as focusing on the sun and the cloud came over and staying covered for the remainder of the afternoon. ]

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Secondary Scope - Focusing using SharpCap Focus Measurements

Having tried focusing solution using PHD2 to provide HFD measurement on a single star,  a new method has been developed using SharpCap to provide a multi-star FWHM measurements.  Whilst SharpCap has manually initiated tools for focusing using a number for methods including single star and mutiple star FWHM measurements including stepping across a range of focus positions using an ASCOM connected focuser,  this was does not provide me with means for fully-automated the task from my Telescope&Camera Control Software (AstroMain), however I can accomplish this by controlling SharpCap using a SharpCap service interface written in python (AstroShCap) that listens and responds to JSON like requests from my control program.

This was accomplished by adding a new routine to my server interface called "RunFWHM monitor" that sets the SharpCap MultiStar FWHM Measurement tool running and reads the FWHM current score when requested, along with 3 new methods 'StartFwhmMonitor',  'MakeFwhmMeasurement', 'GetFwhmScore'.  An existing method 'StopCapture' is used to end the FWHM monitoring.

My Telescope & Camera Control Software (AstroMain) has been updated to call the SharpCap server interface and uses these new methods to help acquire a focus profile and derive a position of best focus.    The older method using PHD2 is still available as an option.

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2019-11-12

Secondary Scope - Focusing with New Backlash Compensation

After determining a good estimate of the true backlash in the system (much larger than previously used) and with my new SharpCap based focusing routine in place there was opportunity to try during night-time observatory testing on 2019-11-12.

- Software : AstroMain 3.17.5, AstroShCap 1.2.8

With backlash compensation value of 1800:

- Focusing in the "In" direction produced an initial best focus position of 8081 steps

- Focusing in the "Out" direction then produced a best focus position of 9560 steps

- Subsequently focusing in the "In" direction produced a best focus position of 7999 steps.

This indicate a total backlash of between 1479 and 1561 steps which is similar to the 1500+/- steps estimated during daytime testing.

Automated Focus Profiles taken on Secondary Scope,  2019-11-12 Orange dots are MultiStar FWHM measurements from SharpCap Profiles are reasonably well formed. Quality of fit suffers due to inclusion of points at one or both ends of the profile (off the bottom of the chart) where SharpCap has returned FWHM Scores of 20.0

Previous calculations  (TS 80mm f/6 APO - Critical Focus Zone, 2018-11-07) has shown that the the critical focus zone for my  80mm TS Photoline APO refractor is just 31 nm (0.031mm).  With my Pegasus Motor Focus Unit  (0.0018mm per step) this is equivalent to 17 steps,  i.e. a zone that is just +/-9 focuser steps wide.   With focusing previously undercompensating for backlash by around 900 steps (1500-400) it is no surprise that focusing was getting screwed up.

(Critical Focus Zone calculation is based on the "New Critical Focus Zone" (NCRZ) equation of GoldAstro, and assumes 1.5” (arc sec) FWHM total seeing and a focus tolerance of 10% .  This CRZ changes to +/- 6 steps for 1" seeing,  +/-11 steps for 2" seeing,  +/-14 steps for 2.5" seeing ,  +/- 17 steps for 3" seeing & +/- 23 steps for 4" seeing. )

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