Change the motor and control circuit of the "celestron advanced vx" to Onstep-based.

The control board used E4 and supports SHC by connecting a line directly to the SD pin to the board and modifying some of the sources.
The PEC sensor uses the AVX's photosensor as it is.
The 470 ohm resistor must be connected to the LED when connected.

The motor used a TS42 cycloid reducer Nema17 stepper motor.

It is also possible to use the Nema17 stepper motor right away, but additional deceleration methods should be considered.

I put the Onstep case separately as the link below.

[https://makerworld.com/ko/models/2348025-onstep-case](https://makerworld.com/ko/models/2348025-onstep-case)