Re: Home sensors


Howard Dutton
 
Edited

On Tue, May 25, 2021 at 07:43 AM, Martin Bonfiore wrote:
Personally, I would prefer to establish a mechanical reference when powering the telescope mount back up using the HOME sensors.  In my implementation, they are opto-interrupters with a few microns of repeatibility error.  On the other hand (based on my understanding which could be mistaken) the designers of Onstep chose to base the PARK/UNPARK operaton on an assumption that the mount and the relationship of the telescope to the mount did not change between power on and power off sessions. 

The case that the scope did not move is for most cases very reasonable in my opinion...any movement would require (for most implementations) back driving a worm gear which is typically not possible and/or bumping the scope such that any clutches slipped.  

While I accept that argument and certainly highly respect the designers (I could not have designed this system), I have been experimenting with changing the software (small modifications) in order to change the HOME with sensors operation to allow the homing after power up approach without needing to redo the alignment.  I am not sure where this will take me...understanding the code has not been easy for me, but certainly an interesting challenge and I have gained a great appreciation of what it takes to provide Onstep functionality.  I am no where close to sharing anything in that regard since my hacking is at the moment, not well understood or tested.
Think this should work in release-4.24 ...

Just find this line in OnStep.ino:
VLF("MSG: OnStep is ready"); VL("");

Then add this one under it:
goHome(true);

Having the mount do an un-commanded rapid motion on startup is not a feature I will be adding.

I understand the appeal of (the option for) doing a home operation before the first Goto and that doesn't seem especially worrisome to me, just takes more effort to stage the events so not trivial and so not something I'll add to 4.24.

Join main@onstep.groups.io to automatically receive all group messages.