Re: Advance Meridian Slew Problems

Chad A

Ray and I have been in extensive communication through email.  There are indeed a couple issues with the counterweight up slews.  He has created a new version ( and I've confirmed one of the bugs is fixed, however, I've just discovered that the bug of a potential pier crash exists (which also existed in the old version).  I will be contacting him this afternoon explaining the pier crash bug I'm referring to (see below).

The CW up slew bug that has been fixed with the new version pertains to the scope slewing to CW down positions when it should have been slewing to CW up advance meridian positions.  With (and probably older versions - I haven't tested), when pointing west of the meridian (highlighted box = E), depending on the value in the "Current" box, when East Limits was checked it often wouldn't slew to CW up when it should have.  This has been completely resolved in and it now slews CW up when E is highlighted regardless of the value in the Current box (so long as the target is within the defined east limits). 

The pier crash bug is complicated but not an uncommon scenario.  It existed in (and probably earlier) and remains in the updated version I've been testing.  If the "CW Up Slews within East Limits" box is checked and "West limits" is unchecked, and the "Current" box has been 'primed' (usually unknowingly) to some sufficiently high value due to slews when the scope is pointing west of meridian (E highlighted) causing the current box to increase, and the scope is then slewed to an east pointing position (W highlighted), and the scope is pointed to certain areas of the sky, and a slew is then issued to a coordinate outside the defined east limits -- it will slew to the CW up position and pier collide.  -- As I said, it's complicated but not very uncommon.  I can make a video demonstrating this if need be.  Additionally, if a user makes the ill-advised choice to manually override the Current box with a high value while W is highlighted (scope pointing east of meridian), that could also lead to a pier crash. -- Ray is aware of this final scenario, but manually overriding the Current box is not something the user should ever chose do while any CW up limits are checked.

This video best demonstrates the issue of not slewing to CW up positions consistently in (and probably earlier), but I don't mention the "primed" pier crash scenario in the video -- I wasn't aware how it could happen when I made the video.  The crash behavior can somewhat be deduced from the video, however.  I misspoke at least once in the video; @ 7:28 I meant to say "this will go into a counterweight UP position."

My opinion is the CW up slew functionality could use a complete overhaul.  As it's currently designed, advance CW up slews (should) only happen when when the scope is pointed west of the meridian (E box highlighted).  This seems an unnecessary limitation.  If only the "East Limits" box is checked ("West Limits" unchecked), the software should slew to CW up positions if the target is within the defined east limits, regardless of where the scope is pointed in the sky (E or W highlighted).  This may require significant revision of the current code.

Regarding the "Next Position" button glitch, it was never an important issue to me, I only brought it to Ray's attention.  We have determined it only happens when the AP V2 ASCOM driver is connected, and disappears when it's not connected. -- so either be aware of it or make sure the ASCOM driver is disconnected when setting meridian limits (preferably the later).

To answer Ron's question.  Yes, you can use the meridian limits edit/next position features to set slewing and tracking limits in any areas you like (but the pier crash bug is not yet resolved - and both slew bugs remain in  You can also manually add points, but I recommend using the Next Position functionality as it's intuitive and works great.



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