Below the Pole Meridian Flip fails with Celestron CGX Mount

ffesl · March 25, 2024, 9:48pm

The “Below the Pole Meridian Flip” is correctly triggered when the time comes, however, SGP instructs my mount (Celestron CGX) to then move into the wrong direction, i.e. it tries to flip by rotating >under< the pier… which obviously fails, the mount crashed against it -20° reserve stops…

Jared · March 27, 2024, 1:44am

SGP does not tell your mount how to get to a specific location…only where to move to. The driver/mount chooses how to get to the actual location. It may be worth contacting Celestron to see if this is a known issue that they may have an updated driver for? Or perhaps there is an invalid setting somewhere in the driver.

SGP commands a pier flip in 2 ways:

By issuing a slew to the same location when you are in a “beyond the meridian” location (this is by far the most common method).
By using an optional SideOfPier property in the ASCOM driver which then invokes a slew similar to 1.

Thank you,
Jared

ffesl · March 27, 2024, 12:35pm

Thank you Jared, I understand.

Before I contact Celestron, could you please have a look at the following 2 log files, one from the sending SGP and one from the receiving CPWI (the Ascom driver sold with the Celestron CGX mount):

****************** SGP-Log: ****************************

[03/25/24 21:50:06.392][DEBUG][Sequence Thread][SQ;] Meridian Flip needed, Seconds Remaining Until Flip Needed 59
[03/25/24 21:50:06.392][DEBUG][Sequence Thread][SQ;] Running blocking meridian flip…
[03/25/24 21:50:06.395][DEBUG][Main Thread][SQ;] Adding sequence level notification: Running automatic pier flip…
[03/25/24 21:50:06.411][DEBUG][Sequence Thread][SQ;] Sending Notification: Status - Running automatic pier flip…
[03/25/24 21:50:06.454][DEBUG][Pier Flip Thread][SQ;MF;] Meridian Flip: Starting Meridian Flip Procedure
[03/25/24 21:50:06.454][DEBUG][Pier Flip Thread][SQ;MF;] Meridian flip: Skipped initial plate solve, use target as reference…
[03/25/24 21:50:06.500][DEBUG][Pier Flip Thread][SQ;MF;] Meridian Flip: Stopping the Auto Guider
[03/25/24 21:50:07.804][DEBUG][Pier Flip Thread][SQ;MF;] Meridian Flip: Sending Telescope command to execute meridian flip
[03/25/24 21:50:07.818][DEBUG][Telescope Thread][SQ;MF;] ASCOM Telescope: Pier side is East
[03/25/24 21:50:07.818][DEBUG][Telescope Thread][SQ;MF;] ASCOM Telescope: attempting pier flip using slew
[03/25/24 21:50:07.819][DEBUG][Telescope Thread][SQ;MF;] Telescope: Slewing to J2000 RA: 22,1669720908986 (22h10m01,10s) Dec: 72,991551286144 (72°59’29,58")
[03/25/24 21:50:07.819][DEBUG][Telescope Thread][SQ;MF;] Telescope: Slew received J2000 coordinates, mount requires JNOW, converting…
[03/25/24 21:50:07.820][DEBUG][Telescope Thread][SQ;MF;] Telescope: Slewing to JNOW RA: 22,1725197411314 Dec: 73,106214748275

/*REMARK: HERE I TURNED OF THE MOUNT AS IT CRASHED AGAINST -20° STOP: */

[03/25/24 21:50:15.631][DEBUG][Telescope Thread][SQ;MF;] ASCOM Telescope: Error in Slew : Must be connected to telescope to use Slewing (ASCOM.NotConnectedException: Must be connected to telescope to use Slewing

END SGP LOG*

****** That’s the Celestron CPWI Ascom driver log ***

2024-03-25 21:50:07.821 +01:00 [#34] (MountService) slew mount requested. raHours:rads decDegrees:rads 22,1725197411314:5,80475209419276 73,106214748275:1,27594415102744
2024-03-25 21:50:07.821 +01:00 [#34] (MountService) J2000 coordinates[rads]. ra dec 5,80329580566086 1,2739439468686
2024-03-25 21:50:07.821 +01:00 [#34] (MountService) Create Slewing task
2024-03-25 21:50:07.821 +01:00 [#34] (MountService) Create DEFAULT Slewing task
2024-03-25 21:50:07.821 +01:00 [Mount_Service_Executor 41#28] (MountService) GotoCoarse (adjusted) 16678793, 3352193

/*REMARK: HERE I TURNED OF THE MOUNT AS IT CRASHED AGAINST -20° STOP: */

2024-03-25 21:50:15.336 +01:00 [Mount_Service_Executor 41#28] (CelestronAuxBus) No response received for: Src=0x20 : Dst=0x10 : Cmd=0x13 : Data[hex]= 01. Attempts remaining: 9
2024-03-25 21:50:15.352 +01:00 [Mount_Service_Executor 41#28] (MountService) Mount service executor reports exception in task: slew to RA = 5,80329580566086 Dec = 1,2739439468686
2024-03-25 21:50:15.355 +01:00 [Mount_Service_Executor 41#28] (Connection) Communication issue reported by Mount

***END CPWI LOG

The CPWI driver (CPWI 2.5.5) from Celestron does not have any useful settings…The ASCOM Profile Explorer shows no entry for the “ASCOM.CPWI.Telescop” except “default = CPWI”

Thanks
Fred

Jared · March 27, 2024, 4:28pm

Those logs indicate what I would assume would happen during a meridian flip (minus the crash!) You see SGP issuing a slew to a set of coordinates and then the Celestron driver slewing to those coordinates via it’s own logic.

This all seems to be fine.

Thank you,
Jared

ffesl · March 27, 2024, 5:31pm

Thanks; I’ll try to take this up with Celestron, not sure were to go to there

bvalente · March 30, 2024, 7:11pm

Fred

"The “Below the Pole Meridian Flip” is correctly triggered "

are you saying there is a specific feature for a ‘below the pole meridian flip’ or is that just a clarification on your part?

thanks

Brian

Jared · March 31, 2024, 1:40pm

There is specific logic in SGP to handle the “below the pole” case but the process of commanding a meridian flip is the same no matter if you’re above or below the pole.

Jared