Re: Help needed with EQ 3-2 mount conversion to onstep.With SynScan motors and gears.

Howard Dutton

Q: OnStep doesn't point where it should

A: There is a problem with your drive design and/or configuration and/or software setup, etc.

Drive design:

  • Motors and drive components move the mount reliably, not slipping or skipping steps.


  • See the Wiki section here for "Preliminary Firmware Configuration" instructions.  Be sure you are not attempting to use settings in Config.h that are being overridden by the "Advanced Configuration" settings stored in EEPROM, you can disable this feature in the SWS or send the :ENVRESET# command from the Arduino Serial Monitor to be sure the Config.h settings are used (which is the default) if you like.
  • Correct stepper micro-step mode is set and actually used in the driver (hardware/connections setup.)
  • Motor direction of motion is correct.
    • Use a planetarium program for control, start tracking; these instructions apply Eq mounts.
    • Move Declination a little (10 or 20 deg.) left and right of the home position (NCP/SCP) and watching from behind the mount see if the telescope movement matches the screen.  Reverse Axis2 if it goes the wrong way.
    • Once that is working do a goto to a point half way up in the sky but not too far in home position (40 degrees away or so.)  If it points down toward the ground RA needs to be reversed.
  • Correct steps per degree settings for Axis1 and Axis2; these instructions apply Eq mounts.
    • Use a planetarium program for control, start tracking.
    • Move Axis2/Declination a fair bit (45 deg.) left or right of the home position (NCP/SCP) and take note of the angular distance traveled, is it about 45 degrees?
    • Move Axis1/RA to near the Meridian and 0 degrees Declination and take note of the angular distance traveled.  Did RA move 90 degrees?

Software setup, etc:

  • Correct date/time and location in both OnStep and any control software.  This includes OnStep UTC Offset and control software time-zone settings.
  • Also be sure to set the mounts start position, etc. correctly as described in the Using OnStep section of the Wiki.

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