Accurate movement with Ioni cube X1

Questions
1

I’m working on a Telescope mount project with a Direct Drive Motorization.

I have two kind of mouvement to use.

first is the “GOTO” function. I send a position to the Ioni and the telescope move to this position. About this part I send the position througt my controller with pulse/direction mode and it work fine.

Second mouvement is the tracking mode. It mean that the telescope have to move at the sideral speed (15 arc sec / seconde).
If I send a pulse signal to the Ioni like i do for the goto, with the encoder resolution that i’ll use, that mean 1 pulse every 20 ms. the problem is that the smoothness of movement is not good…

What could be the best option to set a tracking mode and let the Ioni’s timer to the Job ? One encoder tick every 20ms.

Thank for your help.

2

I would think, that velocity mode would be useful for this. Still, for astronomy purposes you have to consider, that absolute encoder support is not publicly available yet and maximum achievable resolution is not that clear. Best expected seeing is around 0.4…0.5 arcsecond, the smallest movement step should be at least 4 times below this (10 times would be nice). So around 16 million counts per revolution and 0.0775 arcsecond. I tested with 1.6.0 firmware, the maximum achievable resolution was 22…23 bit. 1.6.1 firmware seems to have the limit around 25…26 bit resolution by brief testing.

3

Thank you for your answer

I have two questions

Do I have the possibility to switch between the controle modes (velocity/position) without the PC connection ? not sure…

If yes, How can I set the exact speed through the pulse signal… ? what will be the rapport (rotation speed/Pulse frequency)

If I well understood, the driver won’t use the absolute position from an Absolute encoder. He will just increment or decrement his counter.

Thank you

William

4

I do not know ways to switch mode without PC. This seems more like Argoni area already.
About the resolution - this is not measured positioning accuracy, just movement tests that seemed to behave normally with stated bit depth. It may well be, that the latest firmware has greater bit depth and my hardware is just not rigid enough. Also might be, that there are additional factors limiting real positioning resolution. Tero probably can comment more about this.