David's Astronomy - Notes 2021-10-04 (S921)

Session Aims & Highlights

- Observing Result
- Night Summary Plot
- Session Event Log

Operational Issues

- Critical Issues (0), Major Issues (0), Minor Issues (13), Small Defects (3), Continuous Improvement (9)

Images from 2021-10-04 >> [ Local Files >> ]

2021-10-07

Autoguiding Review

Investigation - Connection to UPB Powerbox lost / Obs.Monitor freezing in 'Monitor Powerbox' (2021-10-07 17:04)

2021-10-07

Introduction

Autoguiding for images taken through 12" LX200 Main Scope is performed using a 80mm secondary scope with ZWO 178MC camera that is attached securely to the LX200. Guiding is perfomed using PHD2 under the control of my automated observatory control program (AstroMain).

The main scope is equatorially mounted and is closely aligned to the celestial pole, but with a bit of misalignment so that Uni-Directional Dec guiding can be used (avoiding Dec backlash issues that would happen if trying to guide in both directions (this is a LX200 mount and not a Paramount !).

The image scale of the guide frames is 1.03"/px (at 1x1 bining), which is a good match for the main scope images that are normally taken (1.40"/px at 3x3 binning to 0.92"/px at 2x2 binning). PHD2 is connected to the ASCOM Scope ast start of session which allows it to use a prior guidescope caibration to make RA corrections that are appropriate to the Scope's Declination.

Current Practice

The current practice is as follows:

After centering the target, guiding is initiated with RA guiding only (no Dec guiding), and the direction of star drift is auto-measured whilst the main scope is autofocused.

- PHD2 is used to autoselect the guide star and guiding is performed using the 'Multiple Stars' option. These both work well.
PHD2's Dec Mode is auto-selected based on the star drift direction and any backlash in Dec is then normally fully taken out before starting the main images.

- Dec Mode 'North' is normally selected when east of the Meridian whilst Dec Mode 'South' is normally selected when west of the Meridian)

- Where rate of star drift is low the selection of required Dec Mode is delayed and may not be set until after the first image frame is taken
Guiding is continued using the same unidirection guide mode until the end of imaging.
The guide scope exposure normally used is 1.5s.

- shorter than 1.5s runs the risk of 'following the seeing', longer than 1.5s delays responding to residual periodic error or other errors in RA

Guiding with telescope tracking east of the Meridian is generally good/acceptable, but guiding with the telescope tracking west of the Meridian is typically poor due to issue keeping guide star locked on Dec position . There is also a few other smaller issues.

Current Autoguding Issues

The following guiding issues are evident :-

When guiding west of the Meridian the guiding will often be ok/acceptable for say the first 3-5 mins, but then there will be 3-5 minute periods when the guide star drifts in Dec (this drift in normally in the direction consistent with that expected from the slight polar misalignment). During this time the Dec pulses appear totally incapable of bringing the star back to the lock position. As some point the star will typically eventually return to the lock position and guiding continues ok again. There may or may not be a repeat of the Dec excursion before the end of the imaging run. See Examples 2 to 4. The start and ends of the guide anomaly can either be gradual or more sharp, and the times when the anomaly happens seems unrelated to when the guiding was initiated. Overall consequence of the issue is that I’m forced to throw away effected frames and/or accept poorer stacked images. This is a continuation of previously reported issue.

- Data shows that there is a wobble in Dec position which is presumed to be an artifcat of sidereal tracking in RA (this is a LX200 mount and not a Paramount ! ).

- Whatever is causing this ‘wobble’ Dec guiding should be able to correct for it. Gravity /loading effects across a 15-18 minute guiding run should be fairly uniform one would think with the effect gradually getting better or gradually getting worse across the run, but not to transition in and out between two separate states ? Some form of cable drag/resistance could be happening, but the issue still happens even after changing cable routing etc, and doesn’t really explain why problem is so much worse everywhere on the west side of Meridian but generally not on the east side. Problem doesn't appear to be due to striction as there is no evidence that the gear system is storing energy - there is no classic 'striction release' of stored energy which would kick the guide star to well beyond the zero line position

- It seems there are sections of the Dec Worm drive / Dec Motor gears where the motion of the Dec Motor is transmitted to the large Dec gear ok and then sections where that motion of the Dec Motor isn’t being transmitted, but with a gravity component so that non-transmission only happens when on one side of the Meridian. I’m thinking a new Dec Motor unit is called for ?
An incorrect Dec Mode can occasionally be selected leading to the guiding being unable to correct for star drift during aquisition of the image frames. This seems to happen due to the impact of large focus position movement or a particular movements of the scope caused by sidereal tracking causing wobble in Declination position.
Delays in selecting Dec Mode can cause jumps in Dec position during acquisution of the first or second mage frame when Dec guiding eventually begins.
Changes in Focuser Position can cause a jump in Dec position either due to the optical difference or change in balance position associated with weight change at back of scope.

- This is more typically associated when there is first a large movement of focuser in one direction before moving the other way to take aout backlash in focuser. Small movements of the focuser where backlash is already removed are not normally associated with any junmps in Dec position.

- Focus position changes and associated jumps in Dec position can occur during autofocusing when star drift is also being measured, prior to the first image due to deferment of focuser movements, changes during imaging due to filter changes oor changes during imaging due to temperature compensation changes.

- Changes are only main at start of imaging frames not during frames themselves but effect of changes in terms of autoguding corrections may effect the first part of the imaging frame.
Guiding is typically thrown off when cloud passes across the target. In this situation it is also better to stop guiding outputs and monitor for an improvement in star visibility rather than continue with full guiding.

Actions

Proposed actions and their current status (Red/Green) are listed below :-

The guiding issue whilst operating west of Meridian has been sent off to Steve Collingwood (SC telescopes) for his further diagnosis, recommendation and assessment of the specific question over whether there would be a benefit in fitting a new Dec Guide Motor Unit ?
Dec Guide Mode should be selected based on Scope Azimuth rather than auto-measured for each target.

There is enough measurements to show that the required Dec Mode correlates with the specific side of the meridian that the scope is pointing to.

The option of returning to auto-measurment of star drift/required Dec mode should be retained in event that telescope is re-aligned at some future point.
Dec Guide mode should be changable during the course of imaging, which might happen when the scope passes across the Meridian or the guide star is off position in Dec and can only be brought back onto lock position by guiding in the opposite Dec direction.

Changes in Dec Mode should in general always be made at the end of an image frame, rather than in the midde of a frame.
A 30s hold should be added to allow guiding to resettle after making chnage to Dec Mode
Imaging should be briefly paused after making a focuser change or a DecMode change to allow sufficient time for autoguiding to reposition the guide star on the lock position
Focus Changes shouldn't be deferred after focusing run but should instead be made directly after focusing if FirstTargetFilter is not "C"

Actions were completed in AstroMain 3.43.4 (2021-10-07), but haven't yet undergone a live session test.

Issue: Connection to UPB Powerbox lost / Obs.Monitor freezing in 'Monitor Powerbox' (2021-10-07 17:04).

Description: Connection to UPB Powerbox lost around 17:04 and led in someway to the Obs.Monitor freezing, with lost of Observatory monitoring, lost of Obs Viewer updates & lost of DewHeater control.    The occcasional temporary loss of the UPB.Switch connection is an ongoing issue. Normally the Service can simply be stopped and restarted, and everthing continues ok (see case at 10:10).

However sometimes the service can not be restarted (see case at 17:04). Trace messages indicates that the restart process gets as far as point 3 (post New ASCOM.DriverAccess.Switch) but doesn't reach point 4 which would normally occur after successfully reconnecting to objPowerBox. Report file shows an AddComment message "PowerBox Switch:" but without the expected follow-up message, either a "Ok" or a "Fail"

It is likely that further progress to restarting the service was held up by a modal dialog box that was presented by UPB driver or Software. Clicking ok on the dialog box the following morning (2021-10-08 10:17) led to "Fail Unable to connect (ASCOM.pegasus_upb.Switch). Twarted by this fail outcome, the 'restart' operation then automatically proceeded with an attempt to restart the UPB Software and Services.   Whilst this restart completed the operation to connect to UPB.Switch failed "Unable to connect (ASCOM.pegasus_upb.Switch)".   It was not until after Services were manually stopped and then restarted did the UPB.Switch connection work normally again.

Time line is as follows:

10:10:45.74 | Observatory Monitor   Restart UPB.Switch Alert 
	| Attempt restart of UPB.Switch due to unexpected disconnection

	10:10:45.84 | Observatory Services  Stop UPB.Switch Ok | Service 
	stopped (B)
10:10:45.84 | Observatory Services  (trace) 
	RestartSwitch(1) Info | Tracing Restart Switch - pre IsNothing(objPowerBox)

	10:10:45.84 | Observatory Services  (trace) RestartSwitch(2) Info | 
	Tracing Restart Switch - post IsNothing(objPowerBox)
10:10:45.87 | 
	Observatory Services  (trace) RestartSwitch(3) Info | Tracing Restart 
	Switch - post New ASCOM.DriverAccess.Switch
10:10:45.87 | Observatory 
	Services  (trace) RestartSwitch(4) Info | Tracing Restart Switch - post 
	objPowerBox.Connected = True
10:10:45.87 | Observatory Services  
	(trace) RestartSwitch(5) Info | Tracing Restart Switch - post AscomName = 
	objPowerBox.Name
10:10:45.87 | Observatory Services  Start 
	UPB.Switch Ok | Service started (Pegasus Powerbox Switch)
> UPB.Switch     
	Alert Unexpected disconnection of UPB.Switch (10:10). Attempting restart...

	PowerBox Switch: Ok    Stopped
PowerBox Switch: Ok    
	Started (10:10) (Pegasus Powerbox Switch)

17:04:51.06 | Observatory 
	Overseer  Check ObsMonitor Info | Obs.Monitor is Pending (6s) in 
	section : Monitor Focuser2
17:04:51.70 | Observatory Worker    
	Check DewHeater Fail | objPowerBox2 is not connected
17:04:52.15 | 
	Observatory Monitor   Check ObsMonitor Info | Obs.Monitor has 
	resumed (cycle = 7.3s)
17:04:52.15 | Observatory Monitor   
	Check ObsMonitor Info | Breakdown (ms) : PowerboxEnv: 4245, Focuser2: 2527,
	
17:04:52.19 | Observatory Monitor   Restart UPB.Switch Alert | 
	Attempt restart of UPB.Switch due to unexpected disconnection
17:04:52.29 
	| Observatory Services  Stop UPB.Switch Ok | Service stopped (B)

	17:04:52.29 | Observatory Services  (trace) RestartSwitch(1) Info | 
	Tracing Restart Switch - pre IsNothing(objPowerBox)
17:04:52.29 | 
	Observatory Services  (trace) RestartSwitch(2) Info | Tracing Restart 
	Switch - post IsNothing(objPowerBox)
17:04:52.36 | Observatory Services  
	(trace) RestartSwitch(3) Info | Tracing Restart Switch - post New 
	ASCOM.DriverAccess.Switch
17:05:01.09 | Observatory Overseer  Check 
	ObsMonitor Info | Obs.Monitor is Pending (9s) in section : Monitor PowerBox

	17:05:06.09 | Observatory Overseer  Check ObsMonitor Alert | 
	Obs.Monitor is Frozen (14s) in section : Monitor PowerBox
17:05:11.10 | 
	Observatory Overseer  Check ObsMonitor Alert | Obs.Monitor is Frozen 
	(19s) in section : Monitor PowerBox
17:05:51.60 | Observatory Worker    
	Check DewHeater Fail | objPowerBox2 is not connected
> UPB.Switch      
	Alert   Unexpected disconnection of UPB.Switch (17:04). Attempting 
	restart...
PowerBox Switch:  Ok      
	Stopped
PowerBox Switch: 


	
	
	
	Next day:
Fail  Unable to 
	connect (ASCOM.pegasus_upb.Switch)

10:17:14.81 | Observatory Services   
	Start UPB.Switch   Fail | Unable to connect 
	(ASCOM.pegasus_upb.Switch)
10:17:14.81 | Observatory Services   
	Start UPB.Switch   Fail | CommandString
10:17:14.82 | 
	Observatory Services   Restart UPB Info        
	| Raising bRestartPowerboxConnection flag
10:17:15.24 | Observatory 
	Monitor    Check ObsMonitor   Info | Obs.Monitor 
	has resumed (cycle = 61,943.1s)
10:17:15.24 | Observatory Monitor    
	Check ObsMonitor   Info | Breakdown (ms) : Powerbox: 61942652, 

	10:17:19.08 | Obs.Manager            
	Start UPB.Restart  Info | Obs.Manager attempting to restart UPB 
	Software & Services
10:17:19.08 | Observatory Services   Stop 
	UPB.Switch      Ok | Service stopped
10:17:19.08 
	| Observatory Services   Stop UPB.Environment Ok | Service stopped

	10:17:19.08 | Observatory Services   Stop UPB.Focuser     
	Ok | Service stopped
10:17:20.28 | Observatory Services   Do 
	MonitorPowerBox Fail | Exception whilst monitoring PowerBox in 
	RunObservatoryMonitoring
10:17:20.28 | Observatory Services   
	Do MonitorPowerBox Fail | Object reference not set to an instance of an 
	object.
10:17:26.96 | Observatory Worker     Check 
	DewHeater    Fail | objPowerBox2 is not 'nothing' 

	10:17:30.23 | Observatory Overseer   Check ObsManager  Alert 
	| Obs.Manager is Frozen
10:17:34.51 | Observatory Services   
	Start UPB.Switch   Fail | Unable to connect 
	(ASCOM.pegasus_upb.Switch)
10:17:34.51 | Observatory Services   
	Start UPB.Switch   Fail | CommandString
10:17:34.58 | 
	Observatory Services   Start UPB.Environment Ok | Service started 
	(Pegasus Astro Environment)
10:17:34.66 | Observatory Services   
	Start UPB.Focuser    Ok | Service started (Pegasus UPB 
	Focuser)
10:18:08.76 | User Action            
	Stop Services Info      | User request to stop 
	observatory services
10:18:08.78 | 
	---------------------------------------------------------------------------------------------------------

	10:18:09.59 | Observatory Services   Stop UPB.Switch      
	Ok | Service stopped
10:18:09.59 | Observatory Services   Stop 
	UPB.Environment Ok | Service stopped
10:18:09.61 | Observatory Services   
	Stop UPB.Focuser     Ok | Service stopped
10:18:53.34 
	| User Action            
	Start Services     Info | User request to start 
	observatory services
10:18:53.36 | 
	---------------------------------------------------------------------------------------------------------

	10:18:53.36 | Observatory Services   Start Services      
	Try | Starting Observatory Services
10:18:53.61 | Observatory Services   
	Start UPB.Switch     Ok | Service started (Pegasus 
	Powerbox Switch)
10:18:53.67 | Observatory Services   Start 
	UPB.Environment Ok | Service started (Pegasus Astro Environment)

	10:18:53.76 | Observatory Services   Start UPB.Focuser    
	Ok | Service started (Pegasus UPB Focuser)

Stopping Powerbox Services 
	2021-10-08 10:17 (Local)
PowerBox Switch: Ok Stopped
PowerBox Env: Ok 
	Stopped
PowerBox Foc2: Ok Stopped

Stopping Powerbox Software 
	2021-10-08 10:17 (Local)
Stopping UPB ** 
> Obs.Overseer Info 
	Obs.Monitor has resumed again (10:17)
** Ok 
Sleeping 2s.. Ok 


	Restarting Powerbox Software    2021-10-08 10:17 (Local)

	Setting UPB serialport    Ok    USB Serial 
	Port (COM6)
UPB                       
	Ok    Started (10:17) (UPB.exe)
Sleeping 5s ...           
	Ok 

Restarting Powerbox Services..
PowerBox Switch:          
	Fail  Unable to connect (ASCOM.pegasus_upb.Switch)
PowerBox Env:             
	Ok    Started (10:17) (Pegasus Astro Environment)
PowerBox 
	Foc2:            Ok    
	Started (10:17) (Pegasus UPB Focuser

Stop Observatory Services 
	2021-10-08 10:18 (Local)
PowerBox Switch:          
	Ok    Stopped
PowerBox Env:             
	Ok    Stopped
PowerBox Foc2:            
	Ok    Stopped
Start Observatory Services 2021-10-08 10:18 
	(Local)
PowerBox Switch:          
	Ok    Started (10:18) (Pegasus Powerbox Switch)
PowerBox 
	Env:             
	Ok    Started (10:18) (Pegasus Astro Environment)
PowerBox 
	Foc2:            Ok    
	Started (10:18) (Pegasus UPB Focuser)

Analysis of the problem

In the event that the problem with the UPB.Switch Connection is not temporary and can't be easily restarted, it leads to the modal dialog box hold-up issue, and the 'restart' operation to freeze. When this happens a separate thread needs to identify that this happened and perform the attempted remedial operation to kill and restart the UPB Software.

It is probably best if the initial attempt to restart UPB.Switch is itself a separate thread so that if the it does stall it doesn't stall the entire main ObsMonitor/ObsViewer loop

If the remedial operation doesn't fix the UPB Switch then run code to stop and restart all UPB services

Restart operation probably requires a 'flag' to indicate that restart is in operation, so that Obs.Monitor & Obs.Worker can skip access to UPB.Switch / Focuser whilst the flag is raised.

Actions
1) Modifty ObsMonitor code to spawn the restart of UPB.Switch as a separate thread (RunRestartSwitch()).
Create flag / timepoint to show the status of thread to highlight a stalled condition (bRunningRestartSwitch (boolean) & StartedRestartSwitchTime (Date)
2) Create code section in Obs.Overseer to spot a 'stalled UPB.Switch restart' and implement remedial operation via a threaded operation (RunRestartUPB)
3) Create and utilise new flag 'bRunningRestartUPB

Changes made to AstroMain 3.43.4 (2021-10-08)

This Web Page:

Notes - Session 921 (2021-10-04)

Last Updated :

2024-09-30

Site Owner :

David Richards

Home Page :

David's Astronomy Web Site

David's Astronomy Pages
Notes - Session 921 (2021-10-04)

Session Aims & Highlights (2021-10-04)

Operational Issues (2021-10-04, S921)

2021-10-07

Autoguiding Review (2021-10-07)

Investigation - Connection to UPB Powerbox lost / Obs.Monitor freezing in 'Monitor Powerbox' (2021-10-07 17:04)

David's Astronomy Pages Notes - Session 921 (2021-10-04)

Session Aims & Highlights (2021-10-04)

Operational Issues (2021-10-04, S921)

2021-10-07

Autoguiding Review (2021-10-07)

Investigation - Connection to UPB Powerbox lost / Obs.Monitor freezing in 'Monitor Powerbox' (2021-10-07 17:04)

David's Astronomy Pages
Notes - Session 921 (2021-10-04)