Re: Offset Init & flip during SGP sequencing


Hi Paul,
I also have an ASCOM compliant dome driver that I wrote myself (it passes the ASCOM conformance test). The dome is an old Pulsar dome that I've done much work on, including building the drive system from scratch. It runs like a dream & I've not previously had any problem with it at all. In fact I don't believe I have a dome problem. I think it's almost certainly how I have the mount configured with the limits. My previous mount ran for 2 years in it perfectly apart from not guiding very well. Hence the Mesu/SiTech upgrade. The only change I've made in SGP is obviously the scope driver, the values for my dome slave settings & unchecking the the "Use Meridian Flip" option. All my other gear is the same.

For a fully automated imaging session my dome behaves as does yours. It stops slewing before anything else happens. I also see "Waiting for Equipment idle".

Any target in the West is fine, over or under the pole. But if I've selected a target in the East everything works just the same (the mount will flip for the GOTO if it needs to), once the scope has slewed to the desired target my filter gets set, then an auto-focus, then a plate solve/offset init.

At this point, unlike in the West however, the mount flips for some reason without the dome slewing first & I don't know why?

When I say flip it's not a genuine flip. It goes to a mirror position on the oposite side of the meridian.

But don't forget SGP's plate solving is still active so SGP just carries on and takes a second plate solving image. In the meantime the dome attempts to repostion itself but it takes time to get there because SGP has a 10sec (mimimum) update frequency + whatever its travel time is. If I'm lucky and the distance is short enough the second plate solve completes and then it will re-flip back to where it should be (on the east of the meridian), re-plate solve and this time continue with the sequence as if nothing has happened.

If I'm unlucky (most of the time) the dome will not reposition in time for the plate solve, SGP will fail into recovery mode.

Last night I watched it go through this loop of events 3 times before I pulled the plug on it.

I'm sure this unwanted 'flip' is purely initiated by SiTech and SGP is totally unaware it's taking place - until the plate solve fails. SGP log files support this.

I'm sure I could just reset my meridian limits to the default, reset SGP to do meridian flips like it did with my old mount and it would be just fine. Except that I wanted to dispense with meridian flips & gain imaging time. Most of my narrow band subs are half an hour so potentially you've lost 30min waiting for a meridian flip. Also I've invested in building a pier & mount that should give me a flipless setup but at the moment I can only image in the WEST.

To be honest I was really surprised to find compulsary track-past & auto-flip in SiTech. I've never had a mount before where you couldn't disable this. Instead I've tried to get round it by playing with the meridian limits & I hope this is be where I'm going wrong. I'm now doubting my understanding of them & just getting more confused.

Many thanks & regards

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