Actual Step

Improving the Tracking Accuracy with PEC

Updated: 2024-04-18

Purpose

This step is recommended from time to time to improve the tracking accuracy of the mount. This chapter has been copied from the iOptron iEQ45 manual.

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PEC Option (Period Error Correction)

You can turn “PEC Playback On” to improve tracking accuracy which is especially useful for long exposure astrophotography. The default status is “PEC Playback Off” when the mount is turned on.

Record PEC

All equatorial mounts have a small amount of worm gear variation that can be corrected using Period Error Correction (PEC). PEC is a system that improves the tracking accuracy of the mount by compensating for variations in the worm gear, and is especially useful for astrophotography without autoguiding. Since the variations are periodic, it is possible to record the corrections needed to compensate for the worm gear variations and play them back to correct the periodic error caused by the variations.


In order to use the PEC function, the Go2Nova® handheld controller must first record the periodic error. The periodic error of the worm gear drive is used to correct the periodic error. It is recommended to use a guide camera to record the PEC with auto-guidance. Here's how to use the PEC function:


  1. Setup the mount with an autoguided telescope by connecting a guide camera via the mount's guide port or ASCOM protocol;
  2. Use MENU=>”Select and Slew” to a bright star and start tracking;
  3. Select MENU=> “Settings” => “Set Guiding Rates”. Set a guiding speed from 0.10X to 0.90X. The default setting is 0.50X;
  4. Start autoguiding per your guiding software;
  5. After guiding is stable, press the BACK button and select “PEC Option” from the menu. Use the ▲ and ▼ scroll buttons to display the “Record PEC” option and press ENTER to start recording the periodic error.
  6. It takes the worm gear 337.5 seconds to make one complete revolution. After 337.5 seconds PEC will automatically stop recording. The PEC value will be permanently stored inside PEC chip on R.A. motor drive until a new data are recorded.
  7. If you want to re-record the periodic error, select “Record PEC” and repeat the recording processes again. The previously recorded information will be replaced with the current information.

PEC Data Integrity

This function checks the integrity of the recorded PEC data.

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