David's Astronomy - Notes 2021-05-06 (S0895)

New Version
A new version of DeviceHub was installed today (2021-05-06) just ahead of session S895. This new version addresses the issue where fast polling for telescope slews was not immediately starting from the time that a slew was requested.

The changes in 6.5.1.3 that are associated with polling are

Change device manager classes to improve polling regularity.
Corrected the telescope manager to start fast polling when a slew starts.
Added logging for polling rate changes.

https://github.com/ASCOMInitiative/ASCOMDeviceHub/releases

Results

Results from session S895 (2021-05-06) showed that the new version operated ok and delivered the fast polling from the point that a slew or jog is requested.

- Fast polling begins straight away. Fresh values from the scope comes through around 1.5s after making slew request (this was delayed by up to 3-4s with previous DH version).

- Polling of a particular telescope property (e.g Altitude) now happens around every 0.9s during fast polling (it was every 1.4-1.5s with previous DH version)
   ( both with fast polling rate (gap time between poll cycles) of 0.5s )

Although the new DH version becomes the ‘official installed version’ (i.e. the one that opens up if you select Device Hub from an ASCOM Telescope Chooser) it is not the version that opens up if I go to certain ASCOM 6.5 SP1 installed shortcuts at Start/ASCOM Device Hub   or Start/All Programs/ASCOM Platform 6/Scope-Dome Hubs/ASCOM Device Hub (though it is the one that opens if I go to Start/All Programs/ASCOM Platform 6/ASCOM Device Hub.

Although the 6.5.1.3 installation says it is removing the previous version of DH this doesn’t fully happen.   The DH 6.5.1.3 install puts its executable & DLLs at C:\Program Files (x86)\Common Files\ASCOM\Telescope, but doesn’t remove DH 6.5.1.0 which remains present at C:\Program Files (x86)\Common Files\ASCOM\DeviceHub (where it was installed by ASCOM 6.5 SP1) and to which the ASCOM Installed Shortcuts remain pointing to.

This may of course be by design. It’s something that I’m aware of and I just workaround it (I open DH from my client program in order to have its window always open on the desktop, rather than having sit as a icon in the notification area, so I have to just make a small change to my code to use the new DH filepath. No problem. )

Effect on Scope Paths

Slew To Near Zenith Focus Point (S895, DeviceHub 6.5.1.3)
81.0 deg slew
34 az/alt points
1.06s average time between az/alt points

ScopePath 
Info | Time: 0.0,  Slewing: 0, Slew: 0.000,  Az: 181.35, Alt: 3.53
ScopePath Info | Time: 1.3,  Slewing: 1, Slew: 0.004,  Az: 
181.37, Alt: 3.53,  Angular Change: 0.004
ScopePath Info | Time: 3.0,  Slewing: 1, Slew: 0.156,  Az: 181.37, Alt: 3.53,  
Angular Change: 0.152
ScopePath Info | 
Time: 3.8,  Slewing: 1, Slew: 4.244,  Az: 181.29, Alt: 3.53,  Angular Change: 4.087

ScopePath Info | Time: 4.8,  Slewing: 1, Slew: 
9.276,  Az: 181.35, Alt: 7.75,  Angular Change: 5.033
ScopePath Info | Time: 6.2,  Slewing: 1, Slew: 14.447, Az: 181.34, Alt: 
12.77, Angular Change: 5.171
ScopePath 
Info | Time: 7.0,  Slewing: 1, Slew: 14.566, Az: 181.35, Alt: 17.93, Angular 
Change: 0.119
ScopePath Info | Time: 7.8,  
Slewing: 1, Slew: 19.616, Az: 181.33, Alt: 17.93, Angular Change: 5.050

ScopePath Info | Time: 8.8,  Slewing: 1, Slew: 
29.288, Az: 181.47, Alt: 22.97, Angular Change: 9.672
ScopePath Info | Time: 10.5, Slewing: 1, Slew: 34.589, Az: 
181.64, Alt: 38.02, Angular Change: 5.301
ScopePath Info | Time: 11.5, Slewing: 1, Slew: 39.553, Az: 181.75, Alt: 42.97, 
Angular Change: 4.963
ScopePath Info | 
Time: 12.3, Slewing: 1, Slew: 44.591, Az: 181.88, Alt: 47.99, Angular Change: 
5.039
ScopePath Info | Time: 13.1, 
Slewing: 1, Slew: 49.628, Az: 181.88, Alt: 47.99, Angular Change: 5.037

ScopePath Info | Time: 13.9, Slewing: 1, 
Slew: 54.571, Az: 182.03, Alt: 53.01, Angular Change: 4.943
ScopePath Info | Time: 14.9, Slewing: 1, Slew: 59.515, Az: 
182.22, Alt: 57.94, Angular Change: 4.944
ScopePath Info | Time: 16.6, Slewing: 1, Slew: 64.547, Az: 182.83, Alt: 67.89, 
Angular Change: 5.032
ScopePath Info | 
Time: 17.4, Slewing: 1, Slew: 69.706, Az: 183.40, Alt: 73.03, Angular Change: 
5.159
ScopePath Info | Time: 18.4, 
Slewing: 1, Slew: 74.699, Az: 184.40, Alt: 78.01, Angular Change: 4.993

ScopePath Info | Time: 19.4, Slewing: 1, 
Slew: 78.754, Az: 184.40, Alt: 78.01, Angular Change: 4.055
ScopePath Info | Time: 20.4, Slewing: 1, Slew: 79.604, Az: 
187.74, Alt: 83.95, Angular Change: 0.850
ScopePath Info | Time: 21.2, Slewing: 1, Slew: 79.943, Az: 188.13, Alt: 84.29, 
Angular Change: 0.338
ScopePath Info | 
Time: 22.2, Slewing: 1, Slew: 80.198, Az: 188.13, Alt: 84.29, Angular Change: 
0.256
ScopePath Info | Time: 23.3, 
Slewing: 1, Slew: 80.513, Az: 187.83, Alt: 84.03, Angular Change: 0.314

ScopePath Info | Time: 24.1, Slewing: 1, 
Slew: 80.674, Az: 187.49, Alt: 83.72, Angular Change: 0.161
ScopePath Info | Time: 25.1, Slewing: 1, Slew: 80.766, Az: 
187.33, Alt: 83.56, Angular Change: 0.092
ScopePath Info | Time: 25.9, Slewing: 1, Slew: 80.804, Az: 187.24, Alt: 83.47, 
Angular Change: 0.038
ScopePath Info | 
Time: 27.7, Slewing: 1, Slew: 80.885, Az: 187.20, Alt: 83.43, Angular Change: 
0.081
ScopePath Info | Time: 28.5, 
Slewing: 1, Slew: 80.917, Az: 187.30, Alt: 83.42, Angular Change: 0.032

ScopePath Info | Time: 29.3, Slewing: 1, 
Slew: 80.943, Az: 187.64, Alt: 83.42, Angular Change: 0.027
ScopePath Info | Time: 30.4, Slewing: 1, Slew: 80.954, Az: 
187.91, Alt: 83.41, Angular Change: 0.011
ScopePath Info | Time: 31.2, Slewing: 1, Slew: 80.957, Az: 188.01, Alt: 83.41, 
Angular Change: 0.003
ScopePath Info | 
Time: 31.8, Slewing: 1, Slew: 80.964, Az: 188.05, Alt: 83.41, Angular Change: 
0.007
ScopePath Info | Time: 33.0, 
Slewing: 1, Slew: 80.967, Az: 188.05, Alt: 83.41, Angular Change: 0.003

ScopePath Info | Time: 34.9, Slewing: 1, 
Slew: 80.972, Az: 188.05, Alt: 83.41, Angular Change: 0.005

Earlier Slew To Near Zenith Focus Point (S894, DeviceHub 6.5.1.0)
81.5 deg slew
26 az/alt points
1.37s average time between az/alt points

ScopePath Info | Time: 0.0,  Slewing: 0, Slew: 
0.000,  Az: 182.44, Alt: 3.50
ScopePath 
Info | Time: 1.1,  Slewing: 1, Slew: 0.004,  Az: 182.45, Alt: 3.49,  Angular 
Change: 0.004
ScopePath Info | Time: 2.4,  
Slewing: 1, Slew: 0.008,  Az: 182.46, Alt: 3.49,  Angular Change: 0.004

ScopePath Info | Time: 3.8,  Slewing: 1, Slew: 
4.938,  Az: 183.41, Alt: 3.94,  Angular Change: 4.930
ScopePath Info | Time: 5.2,  Slewing: 1, Slew: 10.594, Az: 185.10, Alt: 
13.49, Angular Change: 5.657
ScopePath 
Info | Time: 6.6,  Slewing: 1, Slew: 20.463, Az: 186.20, Alt: 18.48, Angular 
Change: 9.869
ScopePath Info | Time: 7.8,  
Slewing: 1, Slew: 25.621, Az: 187.09, Alt: 23.23, Angular Change: 5.158

ScopePath Info | Time: 9.3,  Slewing: 1, Slew: 
30.653, Az: 187.97, Alt: 33.36, Angular Change: 5.031
ScopePath Info | Time: 10.7, Slewing: 1, Slew: 40.378, Az: 
188.48, Alt: 38.36, Angular Change: 9.726
ScopePath Info | Time: 12.1, Slewing: 1, Slew: 45.623, Az: 188.99, Alt: 43.03, 
Angular Change: 5.245
ScopePath Info | 
Time: 13.5, Slewing: 1, Slew: 50.656, Az: 190.46, Alt: 53.24, Angular Change: 
5.032
ScopePath Info | Time: 14.7, 
Slewing: 1, Slew: 60.478, Az: 191.45, Alt: 58.22, Angular Change: 9.823

ScopePath Info | Time: 16.2, Slewing: 1, 
Slew: 65.634, Az: 194.60, Alt: 68.05, Angular Change: 5.156
ScopePath Info | Time: 17.6, Slewing: 1, Slew: 75.235, Az: 
197.49, Alt: 72.98, Angular Change: 9.601
ScopePath Info | Time: 19.2, Slewing: 1, Slew: 78.811, Az: 201.95, Alt: 77.39, 
Angular Change: 3.576
ScopePath Info | 
Time: 20.6, Slewing: 1, Slew: 81.042, Az: 215.24, Alt: 82.74, Angular Change: 
2.231
ScopePath Info | Time: 22.2, 
Slewing: 1, Slew: 81.289, Az: 216.70, Alt: 83.05, Angular Change: 0.247

ScopePath Info | Time: 23.6, Slewing: 1, 
Slew: 81.303, Az: 216.80, Alt: 83.07, Angular Change: 0.014
ScopePath Info | Time: 25.0, Slewing: 1, Slew: 81.347, Az: 
216.67, Alt: 83.05, Angular Change: 0.044
ScopePath Info | Time: 25.8, Slewing: 1, Slew: 81.428, Az: 216.61, Alt: 83.04, 
Angular Change: 0.081
ScopePath Info | 
Time: 27.4, Slewing: 1, Slew: 81.462, Az: 216.58, Alt: 83.03, Angular Change: 
0.034
ScopePath Info | Time: 28.8, 
Slewing: 1, Slew: 81.489, Az: 217.05, Alt: 83.00, Angular Change: 0.027

ScopePath Info | Time: 30.3, Slewing: 1, 
Slew: 81.502, Az: 217.13, Alt: 82.99, Angular Change: 0.013
ScopePath Info | Time: 31.3, Slewing: 1, Slew: 81.508, Az: 
217.19, Alt: 82.98, Angular Change: 0.006
ScopePath Info | Time: 33.1, Slewing: 1, Slew: 81.511, Az: 217.20, Alt: 82.98, 
Angular Change: 0.003
ScopePath Info | 
Time: 34.3, Slewing: 1, Slew: 81.517, Az: 217.20, Alt: 82.98, Angular Change: 
0.006

Issue: Target 9/14 (UGC 11177) and Target 11/14 (GCVS BL Lac) had unusually large Locate Point errors (23.87' & 23.99'/25.37').

Description:

Case 1: UGC 11177's pointing error for Locate Frame 1 was reported as 23.87' when the actual error (from later analysis) was only 3.5'. Rotation angle was reported as 357.2°, which should have been rejected by the MisRotation Test (180 +/- 3°). Despite this the LocateInfo was evidently correct since the target was drawn correctly on the Jpg Picture.

A 23.87' Jog correction was made and Locate 2 gave a pointing error of 0.22' with Rotation angle of 357.2°, when the actual error was 24.9'. LocateInfo again seems to be correct as the target is correctly NOT drawn on the JPG picture (as the target was outside the FOV). Locate Frame1 reports "Checking WCS... Fail WCS center is offset by 25.16 arc mins, Resetting WCS Center (CRVAL1, CRVAL2) to the coordinates determined by image link". which might explain how come the LocateInfo is correct.

Locate Frame 2 reports "Checking WCS... Fail WCS center is offset by 24.75 arc mins, Resetting WCS Center (CRVAL1, CRVAL2) to the coordinates determined by image link"It would seem that PointingError needs to be recalculated in this situation.
Case 2: BL Lac's pointing error for Locate Frame 1 was reported as 23.99' when the actual error (from later analysis) was only 1.9'. Rotation angle was reported as 179.1° which will have passed the MisRotation Test. Despite the large pointing error reported the LocateInfo was evidently correct since the target was drawn correctly on the Jpg Picture.

A 23.87' Jog correction was made and Locate 2 correctly gave a pointing error of 25.37' with the target having been nudged out of the FOV. A correcting jog then brought the target back into FOV on Locate Frame 3 (pointing error 0.3').

Locate Frame1 reports "Checking WCS... Fail WCS center is offset by 25.61 arc mins, Resetting WCS Center (CRVAL1, CRVAL2) to the coordinates determined by image link". which might explain how LocateInfo is correct. It would seem that PointingError needs to be recalculated in this situation.

Analysis

The rotation angle 357.2° in case s not due to a mis-solved plate solution (ie not due to a match to the wrong stars), but is a remnant rotation angle left over from the plate solution of GuideScope reference image from the previous target.
When WCS Center (CRVAL1, CRVAL2) is reset to the coordinates determined by image link the pointing error needs to be recalculated
Why are these Locate Frame Plate Solutions (these two cases and cases in previous 2 sessions) always coming in with a pointing error of around 23 or 24'. It has to be more than coincidence ? Correct, it a consequence of the Invalid WCS centre issue, not a mis-solved plate solution were the resulting pointing error would be much more random. Fixed in AstroMain 3.39.11

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	Operational Issues
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	Images from 2021-05-06 >> [ Local Files >> ]

	DeviceHub 6.5.1.3
	Investigation - Abnormal Pointing Errors & Centering Failures

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Investigation - Abnormal Pointing Errors & Centering Failures

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Notes - Session 895 (2021-05-06)