- Association Astrimage

Integration of PicAstro to the system of observation

The first purpose of the interface PIC-ASTRO is to manage a mount EQ5 equipped with its motors of origin, henceforth compatible with other mounts. The set in functioning consists of the following elements:

A German equatorial mount motorized by motors step by step
The interface PIC-ASTRO and its hand controller (PAD)
A battery12V, a power supply or other power source of 12V continuous
A computer for GoTo functionnalities
A webcam, a PC equipped with a software for tracking like Iris or a CCD caméra with traking mode like SBIG ST4 ou STV
A null serial cable ( 3 conductors) allowing to connect the PC to the PIC-ASTRO

Material evolutions

With the addition of 2 standard cases TTL the interface authorizes, since the version 2, the possibility to command micro steps motors. This way of functioning allows to smooth the rotation of the axis of motors and so to have a more soft movement. The function micro-steps can be use with the original motors of the mounts, in that case, it does not modify the performances. Micro-steps are particularly well exploited with one motors step by step powerful (eg: Nanotec ST4209L1704-A) equipped with a reducer from 3 to 4. This reducer maybe realized either with gearings or with pulleys and belt. The interest of belts being to allow the supression of the Thresholds, this method allows to obtain a high speed for GOTO, this speed being dependent on the used motors and on the reduction. According to the configuration this speed can reach 1500x the sidereal speed but, not to damage the mechanics of mount, it is wiser not to exceed 200x, against a maximum speed about 35x the sidereal speed with the motors of origin. A second evolution is the possibility of using one of the entries of the microcontroller to synchronize the PEC.

Astronomical functionnalities

The interface of PIC-ASTRO controls the motors as any classic hand controller of the motors of the mount. Axis of Right ascension: the tracking is permanently made by the microcontroller so as to compensate the rotation of the earth, the corrections and the movements can be made by the PAD with diverse speeds. Axis of Declination: the corrections and the movements can be made by the PAD with diverse speeds. Focus motor: a switch allows to change the functions of the buttons of the PAD between the movements on the axes of right ascension and declination or the command of the focus motor. The coverage of the commands of the protocol Meade LX200 allows to command the system in a automatic way by a PC or quite other device capable of communicating via a serial port RS232. This protocol allows to give miscellaneous orders to pic-astro :

Move on right ascension axis
Move on declination axis
Motor commands of the focus motor : certain software of imaging knows how to adjust in a autonomous way this parameter.

The coverage of this protocol opens the door towards features evolved in Goto, autoguiding assisted by PC, imaging CCD assisted etc....

Functioning Principles of the software

Two big parts have to be separated in the software used in PicAstro: a BootLoader: it is a quite small software which allows the microcontrollor (the "brain" of PicAstro) to understand commands which are sent to it via the serial connection with the PC, and so to download the software by itself. It contains no appropriate logic for the functioning of PicAstro. The interest of a bootloader is to have to program only once the microcontrollor, the operation asks for the use of a programmator. The PicAstro software: it is the software of management of the interface by itself, which allows to run it, to interpret the LX200 commands, to command motors etc.... It is adapted to the technical specifications of the mount : Number of teeth of the cog, the specifications of the motors, the system of reduction (gearings, pulley / belt). Compatibility and evolutions For material reasons, the PicAstro V1 software. XX is not compatible with the version 2 of the interface and conversely. The software for the version 2 of the interface PIC-ASTRO are compatible with the original motors of the mount, and allow the exploitation of the Material evolutions, mainly the management of microsteps.