David's Astronomy - Notes 2021-04-24 (S0890)

Issue : Scope paths during slews in the latest S890 session using the MeadeGeneric (1.0.1.327) telescope driver are less well resolved than scope paths in earlier sessions using the MeadeLX200GPS driver. Scope paths appear more obviously as a series of straight line segments in chart based on MeadeGeneric driver compared to chart based on MeadeLX200GPS driver.

Description :

Picture below shows the scope slewing path in S890 session using MeadeGeneric (1.0.1.327) telescope driver (right-hand graph)
Picture below shows the scope slewing path from an earlier sssion using the MeadeLX200GPS telescope driver (right-hand graph)
Slewing charts from both session was created in AstroMain using data passed on by DeviceHub.Telescope, with DH fast polling rate of 0.5s and an AstroMain poll rate of 0.2s.
Scope Paths are less smooth on the first chart (using MeadeGeneric driver) compared to the second chart (using MeadeLX200GPS driver)

Analysis:

Examining the opening slew from near the Park Position to the Near Zenith Focus Point from the two sessions
Scope slewing path (00:03) collected in S890 session (using MeadeGeneric (1.0.1.327) driver).

Path for the 80 deg slew is defined by 16 unique Az/Alt points.

00:03:42.92 | Az: 181.43, Alt: 3.20, Slewing: 0, Slew: 0.000, Time: 0.1 00:03:45.05 | Az: 181.44, Alt: 3.20, Slewing: 1, Slew: 0.004, Time: 2.2 00:03:49.55 | Az: 181.27, Alt: 6.84, Slewing: 1, Slew: 8.669, Time: 6.7 00:03:51.17 | Az: 181.31, Alt: 11.86, Slewing: 1, Slew: 18.798, Time: 8.3 00:03:51.98 | Az: 181.48, Alt: 27.25, Slewing: 1, Slew: 29.025, Time: 9.1 00:03:54.41 | Az: 181.77, Alt: 41.80, Slewing: 1, Slew: 38.608, Time: 11.6 00:03:56.82 | Az: 182.06, Alt: 52.00, Slewing: 1, Slew: 53.808, Time: 14.0 00:03:59.05 | Az: 182.88, Alt: 62.05, Slewing: 1, Slew: 63.888, Time: 16.2 00:04:01.48 | Az: 183.94, Alt: 76.88, Slewing: 1, Slew: 73.703, Time: 18.6 00:04:04.52 | Az: 186.71, Alt: 82.61, Slewing: 1, Slew: 80.072, Time: 21.7 00:04:07.16 | Az: 187.80, Alt: 83.20, Slewing: 1, Slew: 80.178, Time: 24.3 00:04:09.39 | Az: 187.69, Alt: 83.38, Slewing: 1, Slew: 80.264, Time: 26.5 00:04:11.67 | Az: 187.28, Alt: 83.38, Slewing: 1, Slew: 80.320, Time: 28.8 00:04:14.30 | Az: 187.69, Alt: 83.38, Slewing: 1, Slew: 80.365, Time: 31.4 00:04:15.93 | Az: 187.78, Alt: 83.38, Slewing: 1, Slew: 80.369, Time: 33.1 00:04:17.97 | Az: 187.78, Alt: 83.38, Slewing: 1, Slew: 80.375, Time: 35.1 00:04:18.01 | Total: 80.375, Direct: 80.602 00:04:18.01 | Scope Slew Time= 35.1s

Although DH is being polled every 0.2s or so by client program, changes in position are only being detected every 2.33s or so.
Scope slewing path (21:40) collected in S885 session (using MeadeLX200GPS driver )

Path for 81 deg slew is defined by 25 Az/Alt points.

21:40:21.58 | Az: 180.42, Alt: 1.76, Slew: 0.000, Time: 0.3 21:40:24.93 | Az: 180.43, Alt: 4.51, Slew: 2.764, Time: 3.7 21:40:26.15 | Az: 180.37, Alt: 9.55, Slew: 7.824, Time: 4.9 21:40:27.57 | Az: 180.27, Alt: 14.55, Slew: 17.775, Time: 6.3 21:40:28.79 | Az: 180.29, Alt: 24.44, Slew: 22.770, Time: 7.6 21:40:30.21 | Az: 180.31, Alt: 29.46, Slew: 27.804, Time: 9.0 21:40:31.64 | Az: 180.33, Alt: 34.36, Slew: 37.731, Time: 10.4 21:40:33.06 | Az: 180.37, Alt: 44.38, Slew: 42.781, Time: 11.8 21:40:34.28 | Az: 180.40, Alt: 49.34, Slew: 52.523, Time: 13.0 21:40:35.70 | Az: 180.43, Alt: 54.08, Slew: 57.697, Time: 14.5 21:40:37.04 | Az: 180.53, Alt: 64.24, Slew: 62.720, Time: 15.8 21:40:38.25 | Az: 180.61, Alt: 69.16, Slew: 72.455, Time: 17.0 21:40:39.67 | Az: 180.73, Alt: 73.94, Slew: 76.738, Time: 18.4 21:40:41.09 | Az: 181.21, Alt: 81.57, Slew: 80.119, Time: 19.9 21:40:42.51 | Az: 181.33, Alt: 82.45, Slew: 80.991, Time: 21.3 21:40:43.93 | Az: 181.35, Alt: 82.63, Slew: 81.003, Time: 22.7 21:40:45.15 | Az: 181.35, Alt: 82.59, Slew: 81.071, Time: 23.9 21:40:46.37 | Az: 181.34, Alt: 82.57, Slew: 81.085, Time: 25.1 21:40:47.58 | Az: 181.34, Alt: 82.55, Slew: 81.163, Time: 26.3 21:40:48.80 | Az: 181.35, Alt: 82.54, Slew: 81.196, Time: 27.6 21:40:50.42 | Az: 181.89, Alt: 82.54, Slew: 81.219, Time: 29.2 21:40:51.44 | Az: 181.99, Alt: 82.54, Slew: 81.235, Time: 30.2 21:40:52.65 | Az: 182.04, Alt: 82.53, Slew: 81.244, Time: 31.4 21:40:53.67 | Az: 182.04, Alt: 82.53, Slew: 81.247, Time: 32.4 21:40:55.30 | Az: 182.05, Alt: 82.53, Slew: 81.250, Time: 34.1 21:40:55.32 | Total: 81.250, Direct: 81.307

The slew using the MeadeGeneric driver captures fewer Az/Alt points (just 16 points) than the equivalent slew using the MeadeLX200GPS driver (25 points).

Average time interval between unique Az/Alt coordinates is 2.19s to 2.33s with MeadeGeneric driver. This compares with an average time interval of 1.32s using the MeadeLX200GPS driver.

(Note: earlier time data is limited in both datasets due to a delay in the DeviceHub switching between slow polling and fast polling rate. This is will be fixed in a future DeviceHub version, this might add 1 or 2 extra points per slew path.)

(It is understood that Az/Alt values returned from MeadeGeneric are calculated from Scope Ra/Dec. Apparently the reason for this is that driver's author found a huge problem in the Meade firmware on the Autostar whereby it appeared to be returning the wrong co-ordinates. )
The log file for slew using the MeadeGeneric driver has ' Angular Change: 0.00 (Static)' lines beyond the initial 'static phase' (related to DH poll rate issue), whilst the log file for slew using MeadeLX200GPS driver doesn't contain this later 'Static' lines. This potentially relates to differences between frequency at which Ra/Dec coordinates are updated by driver compared to update rate for Az/Alt coordinates, and the method used for reporting the scope path.
Examining the Meade.Generic.Telescope trace file for part of the slew we can see a series of polling cycles which are illustrated below:

00:03:50.129 RightAscension Get - 13:03:16 convert to 13.0544444444444 13:03:16 00:03:50.519 Declination Get - -05[DF]25:07 convert to -5.41861111111111 -05:25:07" 00:03:50.519 Altitude 27.2527125979371 00:03:50.893 RightAscension Get - 13:03:16 convert to 13.0544444444444 13:03:16 00:03:50.956 Declination Get - -05[DF]32:15 convert to -5.5375 -05:32:15" 00:03:50.971 Azimuth Get 181.479382801732 00:03:51.455 Declination Get - -00[DF]27:19 convert to -0.455277777777778 -00:27:19" 00:03:51.595 RightAscension Get - 13:03:16 convert to 13.0544444444444 13:03:16 00:03:53.015 RightAscension Get - 13:03:37 convert to 13.0602777777778 13:03:37 00:03:53.171 Declination Get - +09[DF]07:39 convert to 9.1275 09:07:39" 00:03:53.171 Altitude 41.7984043866063 00:03:53.436 RightAscension Get - 13:03:16 convert to 13.0544444444444 13:03:16 00:03:53.842 Declination Get - +09[DF]13:13 convert to 9.22027777777778 09:13:13" 00:03:53.857 Azimuth Get 181.77059038713 00:03:53.998 Declination Get - +09[DF]07:39 convert to 9.1275 09:07:39" 00:03:54.060 RightAscension Get - 13:03:16 convert to 13.0544444444444 13:03:16 00:03:55.402 RightAscension Get - 13:03:39 convert to 13.0608333333333 13:03:39 00:03:55.573 Declination Get - +19[DF]20:04 convert to 19.3344444444444 19:20:04" 00:03:55.573 Altitude 52.0037541326065 00:03:55.839 RightAscension Get - 13:03:16 convert to 13.0544444444444 13:03:16 00:03:56.213 Declination Get - +19[DF]24:20 convert to 19.4055555555556 19:24:20" 00:03:56.213 Azimuth Get 182.062013116076 00:03:56.338 Declination Get - +24[DF]19:39 convert to 24.3275 24:19:39" 00:03:56.431 RightAscension Get - 13:03:16 convert to 13.0544444444444 13:03:16
Observations are :

1) average time interval between successive RA/Dec points is 0.78s (some are around 0.27s others around 0.84, others around 1.31s)

2) average time interval between RA reads and the corresponding DEC reads is normally 0.10s (but not all RA read have an obvious matching Dec read)

3) average time interval between successive Altitude/Azmiuth points is 2.48s (range 2.31 to 3.14s)

Recommendation : Altitude/Azimuth reads should be made at the fast polling rate during slews in order to try to achieve a more most accurate & higher resolution Az/Alt path

4) average time interval between Altitude reads and the corresponding Azimuth reads is 0.70s (range 0.23 to 0.83s)

Recommendation : Azimuth reads should be made directly after Altitude reads in order to try to achieve the most accurate Az/Alt path )
Nornal cycle (when not slewing) looks like this

01:06:27.872 SiteLongitude Get -02[B0] 00' 32" 01:06:27.872 SiderealTime Get - 14.1893042388873 01:06:27.872 Connected Get True 01:06:27.872 Connected Get True 01:06:27.872 GetSlewing Result = False 01:06:27.872 Slewing Result = False 01:06:27.872 Connected Get True 01:06:27.872 TargetDeclination Get 0.608344444444444 01:06:27.872 Connected Get True 01:06:27.872 TargetRightAscension Get 14.3191305555556 01:06:27.872 Connected Get True 01:06:27.872 Tracking Get - True 01:06:27.872 Connected Get True 01:06:27.872 TrackingRate Get driveSidereal 01:06:27.872 Connected Get True 01:06:27.887 UTCDate Get started 01:06:27.965 RightAscension Get - 14:19:12 convert to 14.32 14:19:12 01:06:27.965 AtPark Get - False 01:06:28.121 UTCDate Get - 04-25-21 00:06:23 01:06:28.168 Declination Get - +00[DF]36:22 convert to 0.606111111111111 00:36:22" 01:06:28.168 PulseGuide Complete Before RA: 14:19:13 Dec:00[B0] 36' 22" 01:06:28.168 PulseGuide Complete After RA: 14:19:12 Dec:00[B0] 36' 22" 01:06:28.168 IsPulseGuiding Get pulse guiding is synchronous for this driver 01:06:31.132 Connected Get True 01:06:31.132 Connected Get True 01:06:31.132 UTCDate Get started 01:06:31.226 UTCDate Get - 04-25-21 00:06:26

Anomalies
TheSky appears to request Ra/Dec on up to 3 occasions at the same time, or DeviceHub is sometime reporting Get RA/Dec message up to 3 times for the same request from TheSky

Actions:

MeadeGeneric. Send a heads-up report on this issue to author of MeadeGeneric for his information.
MeadeGeneric. Send a more detailed description of this issue to author of MeadeGeneric for review & action (if appropriate)

Update 2021-04-27

Issue fixed in MeadeGeneric 1.1.0.337 which is confirmed to show improved performance.

For LX200GPS scope Az/Alt values are now taken directly from the scope. This eliminates the retrieval of UTCDate, SiteLongitude, SiteLatitude, RightAscension and Declination from scope that are necessary for maths calculation to workaround a firmware bug in 44Eg (older Meade scopes/Autostar versions) where
:GA# was returning the Dec, not the Altitude!)

For an 80 arc deg slew the associated Az/Alt slew path now has 22 points constructed along it compared to only 12-14 points previously for an equivalent slew. The average time between positional changes now comes in as 1.6s compared to 2.4s earlier. This new result (1.6s) is not too far off previous results using the MeadeLX200GPS driver (1.3s)
Issue confirmed to have been fixed in further testing on 2021-04-27. Version 1.1.0.327 confirmed to show a performance that is similar to MeadeLX200GPS Driver.

For an 85 arc deg slew the associated Az/Alt slew path now has 26 points (average 1.38s between points) using MeadeGeneric 1.1.0.327 driver. This new result is very similar to a similar 83 deg slew using the MeadeLX200GPS driver which had an Az/Alt slew path with 24 points (average 1.32s between points).

Update 2021-04-30

MeadeGeneric 1.1.0.337 driver used for session S893 (2021-04-30).
Scope slewing paths are better resolved that the earlier driver version and slew paths are more curved.
Picture below shows the scope slewing paths from session S893 (right-hand graph), using MeadeGeneric 1.1.0.337 driver.


	Session Aims & Highlights
	- Observing Result - Night Summary Plot - Session Event Log

	Operational Issues
	- Critical Issues (0), Major Issues (0), Minor Issues (4), Small Defects (2), Continuous Improvement (0)

	Images from 2021-04-24 >> [ Local Files >> ]

	Investigation - Slewing Scope Path Resolution

This Web Page:	Notes - Session 890 (2021-04-24)
Last Updated :	2024-09-30
Site Owner :	David Richards
Home Page :	David's Astronomy Web Site

David's Astronomy Pages
Notes - Session 890 (2021-04-24)

Session Aims & Highlights (2021-04-24)

Operational Issues (2021-04-24, S890)

Investigation - Slewing Scope Path Resolution

David's Astronomy Pages Notes - Session 890 (2021-04-24)

Session Aims & Highlights (2021-04-24)

Operational Issues (2021-04-24, S890)

Investigation - Slewing Scope Path Resolution

David's Astronomy Pages
Notes - Session 890 (2021-04-24)