Aspect User Documentation

Purpose

Aspect was created to semi-automate the process of teaching PEC (periodic error correction) for Rajiva's EQ6/HEQ5 MCU Upgrade kit and the LittleFoot astronomical mount stepper controler.

From v0.4 on, Aspect's basic functionality is there. It's quite sparsely tested, however, and bears a lot of assumptions from my side on how PEC is implemented in the LittleFoot firmware. And there are some rough edges usability wise, for sure. See the Aspect Changelog for current state.

Many thanks to the friendly people at the LittleFoot support forum who contributed to this project, especially Rajiva, Doug and Christian.

Preparations

You need

• a serial connection to the LittleFoot/MCU
• Doug Dieter's MCU Control Plus, version 2.1.7 or higher (2.1.4 won't work, as it lacks the required logging feature while followin a star)
• a webcam that could be used for autoguiding with MCU Control Plus
  you don't need a guiding scope, you can use your main optics for measuring
• clear skies

Quick Guide

This is a minimal description of the workflow, you might want to read the more verbose Walkthrough first (as soon as its written ...).

• Set PEC off and measure PE for at least one cycle in MCU Control Plus
  • Choose a guide star close to the celestial equator and far away from the horizon, if possible. Remember the guide star's declination.
• Generate a PEC table in Aspect:
  • tab MCU :
    • choose serial port, and press "refresh" to see if communication is ok
      in case of problems, check the MCU log window (accessable from menu "Help")
  • tab PE Raw Data:
    • import PE file
  • tab PE Processing:
    • set Smoothing Width to eliminate seeing and short jumps
    • set First Sample and Last Sample to cut away bad samples at the beginning and/or end of measurement
    • set Star Dec to the declination of the guide star you used while measuring with MCU Control Plus
    • play with Drift so that cycles match as good as possible
    • set Scale to -1 if PE doubles with PEC, i.e. PEC makes things worse instead of better
  • tab PEC Table:
    • set PEC Factor to 1 ; Aspect so far is testet with value 1 only
    • set Worm Wheel Teeth to what's apropriate for your mount; optionally query from the MCU by pressing the Query button
    • leave PEC Table Traversal and PEC Acceleration as is for now
    • press the Calculate PEC from PE button
    • play with the Graph Offset to see how well or bad PE and the generated PEC match; maybe switch away the Raw PE graph with the checkbox below the chart area
    • upload the PEC table to the MCU by pressing the Put button, or save it to a file with Save As and restore it with MCU Control Plus

Optionally do a dry run to verify if the generated PEC table makes the MCU moves the worm as intended, to get the required position profile for compensating the PE:

• in Aspect:
  • tab PEC Profile:
    • maybe adjust Polling Interval (a poll every 0.5 seconds work fine for me, but 2 or 3 seconds should do as well)
    • press Start
      Attention: this sets tracking speed to Sidereal and switches off IntellyTrack.
    • let run for at least one cycle
    • press Stop
    • adjust Graph Drift to make the purple graph run into it's beginning at the end of the first cycle; all cycles should match then.
    • use Graph Offset to move the purple PEC Profile graph match the green PEC graph as good as possible
  • if peak-to-valley of purple and green graph differ, reiterate PEC generation:
    tab PEC Table:
    • adjust PEC Acceleration such that green and purple graph span same amplitude
    • press the Calculate PEC from PE button
    • upload PEC table to MCU and do another PEC profile run

Now verify how good/bad the generated PEC table works under the sky:

• Set PEC to on and redo measuring PE for at least one cycle in MCU Control Plus (select a different PEC log file than before, as this is the result of PE correction now)
• Load PEC log into aspect
  • drift-compensate, scale and smooth as above
  • the resulting red graph ideally should become a flat horizontal line; you can read the remaining PE in arcseconds from the left scale (peak-to-valley; absolute values are not relevant)

Walkthrough

Todo:

Write this ...

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