Late last year I reported that the Meridian Flip process was failing. In the interim, I have had little opportunity due to the weather to carry out further trials. Recently however, during a run on NGC 5128 an opportunity arose whereby a meridian flip was necessary. It failed again and I got the same error message as previously. This is a DropBox link to the log file and a picture of the log entries around the time the flip was required.
The log shows:
“FlipWait: ending wait due to telescope parked or not tracking” …then
“Aborting Sequence: User aborted meridian flip”
There is clearly some conflict between what SGPro is sending to the Mount to initiate a flip and what the Mount is doing, in terms of which side of the pier the OTA ends up.
In terms of The SkyX, there are software slew limits which can be set, in the worst case, to prevent the OTA hitting the pier. I have set mine to 1.5 hours before and after the Meridian. If the OTA is pointing anywhere within this envelope, it is possible to press the “Flip Mount Now” button on The SkyX which will cause the Mount to flip to the other side of the pier. Outside the envelope it is not possible to flip in this manner.
The other parameter for The SkyX is the “Flip Hour Angle”. Remembering I am in the Southern hemisphere, when set to zero and a slew is initiated, the OTA will go to the west side of the pier if the celestial object has not yet reached the meridian i.e. still on the east side. Conversely once the object has passed the meridian, moving east to west, the OTA will move to the other side of the pier, i.e. the east side if it is asked to slew to that object. If not asked to slew it will continue until the slew limit is reached.
If the Flip Hour Angle is set to -1 hour, then if one slews to an object that is approaching within 1 hour of the Meridian or after, the OTA will move to the east side of the pier. Conversely if the Mount is asked to point to an object that is still more than 1 hour before the Meridian, the OTA will slew such that it is on the west side of the pier.
If the Flip Hour Angle is set to +1 hour, then if the Mount is asked to slew to an object either before the Meridian or up to 1 hour afterwards, the OTA will be on the west side of the Meridian. However, if more than an hour after the Meridian the OTA will be on the east side of the pier.
I am thinking that there could be conflict between which side of the pier SGPro wants the OTA to be on after a flip and where The SkyX will send it when asked to slew to an object.
When SGPro wants to initiate a Meridian Flip, what does it tell The SkyX to do? Does it issue a command to flip to the other side of the Mount (just like the Flip the Mount option on The SkyX, where it forces a Flip to the other side of the Mount) or does it simply tell the Mount to slew to the RA/ Dec coordinates of the target relying on The SkyX to flip if appropriate?
To my way of thinking, the parameters set in SGPro for the Meridian Flip must be consistent with the Flip Hour Angle Set for The SkyX.
So for example, supposing my maximum exposure time is 30 mins and I would like any exposure started before the meridian to complete and thence for a Meridian Flip to occur.
I should set the “Minutes Past the Meridian Flip” to say 32 mins. Therefore if it is one minute before the Meridian when an exposure is due, it will be started and finished before the flip. Ignoring the download time, the exposure will be complete by 29 mins past the Meridian. However, a new image will then start and will be interrupted by the specified flip time at 32mins past the Meridian. Therefore the “Wait for the Meridian” tick box should be ticked such that another exposure is not started. At 32 mins past the Meridian SGPro should initiate the flip. Does this initiate the “pre-flip” image which is plate solved as a reference for the flip? In any case at this point the OTA should be on the west side of the pier for the Southern Hemisphere. If SGPro orders a flip and The SkyX is capable of acting on such a command, the Mount should move the OTA to the other side of the pier to point to the same coordinates. The 'Auto Centre After Meridian Flip" tick box should be ticked to ensure that an Auto Centre aligns the OTA to the pre-meridian flip coordinates.
If however, SGPro relies on The SkyX to flip the Mount to the other side of the pier, then the Flip Hour Angle would need to be consistent with this and should be set to +30 mins. This would mean that any Auto Centring before this time would retain the OTA on the west side of the pier, but a command to slew to RA/Dec coords after this time would result in the OTA moving to the east of the pier, effectively performing a Meridian Flip.
Could you please firstly clarify how the Meridian Flip command from SGPro to The SkyX works and secondly, whether the above logic holds in terms of the settings for the Flip Hour Angle in The SkyX.
I did not pay much attention to the Flip Hour Angle previously which may explain why the Meridian Flips have fallen over.