Imaging starts before slew finishes - ASCOM shortcomings?


#1

When my CEM60 is doing a flip across meridian (not an automatic flip - that’s another thread :smile:), it begins the plate solve image before slewing has stopped. I know that I can increase the mount settle time to compensate for this but I’m curious - is there a parameter in the ASCOM driver and/or SGP that should be reporting that the mount is still slewing and not to start imaging yet?

I don’t remember it happening with my Celestron AVX but I don’t remember if I already had the settling time high due to the backlash issues.

Thanks for any info,
Chris


#2

It looks as if this particular driver has implemented the ASCOM protocol incorrectly.

There are two types of slew specified - Slew and SlewAsync. The Slew methods should not return until after the slew has completed and the SlewAsync methods will return immediately.

There is also a Slewing property, this returns true if a slew is in progress.

Jared and Ken haven’t got this wrong, nor is it wrong for the Celestron mounts. If it was lots of people would have noticed.

It looks as if the driver is returning from a Slew command before the slew has completed. From what I hear it isn’t the only thing that’s wrong with this driver.

The ASCOM support components has a Conform application that we hope that driver developers will use to check the basic operation of the driver. I think it would have picked this up. Users can also try this, it’s part of the ASCOM developer package.

Chris


#3

I ran the conform test a few days ago. These were the only issues it returned:

22:22:48.520 MoveAxis Primary OK Can successfully set a movement rate of zero
22:22:48.630 MoveAxis Primary OK Exception correctly generated when moveaxis set below lowest rate (0.00208333333333333)
22:22:48.739 MoveAxis Primary OK Exception correctly generated when moveaxis set above highest rate (4.75)
22:22:52.920 MoveAxis Primary OK Successfully moved axis at minimum rate: 0.00416666666666667
22:22:54.979 MoveAxis Primary ISSUE Slewing incorrectly remains true after stopping positive axis movement, remaining test skipped
22:22:55.010 MoveAxis Secondary OK Can successfully set a movement rate of zero
22:22:55.088 MoveAxis Secondary OK Exception correctly generated when moveaxis set below lowest rate (0.00208333333333333)
22:22:55.462 MoveAxis Secondary OK Exception correctly generated when moveaxis set above highest rate (4.75)
22:22:59.565 MoveAxis Secondary OK Successfully moved axis at minimum rate: 0.00416666666666667
22:23:03.637 MoveAxis Secondary ISSUE Slewing incorrectly remains true after stopping negative axis movement, remaining test skipped
22:23:03.668 MoveAxis Tertiary OK .NET - Feature not implemented

What I have found also is that the conform test doesn’t always catch things. The iOptron driver has always passed side of pier conformance tests.

Chris


#4

Fortunately the developer of Conform is telepathic. Your noticing this means that you need do nothing more to let him know about this.

Or maybe not.


#5

Now that I have SideofPier working correctly (testing new driver from iOptron) it’s on to this issue with iOptron. Hopefully this is an easy one. I had to put in a 60 sec mount settling time in SGP to keep imaging from starting too early.

Chris


#6

Can you attach the entire Conform results? I believe it tests for the slew case that you’re seeing. Just FYI it’s not the “Move Axis” it would be denoted as Slew or SlewAsync as Chris R mentioned.

Thanks,
Jared


#7

Conform 2219.33102.txt (19.6 KB)

Here you go. This is on the v3.2 driver.

Chris


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