Collecting and Using Periodic Error Tracking Data

If you own the PrecisionPEC software, have your computer and imaging system meets the minimum system requirements, and now want to get the best possible periodic error correction curve possible, follow steps 1-4 in the table below.

 

Step

Description

1.

 

Collect Tracking Data to Quantify Periodic Error

 

The first step is to obtain the "tracking" data for your Paramount that will quantify the mount's periodic error. This means that you'll be tracking on a star, without making any tracking corrections. You must be able to place a star on your imaging CCD detector, and then keep the star in the tracking box without making any corrections to the mount for ten to fifteen minutes (several periods of the worm).

 

The Paramount, TheSky6 and CCDSoft must configured correctly to:

 

  • Disable periodic error correction in CCDSoft

  • Disable autoguiding in CCDSoft

  • Disable ProTrack in TheSky6

  • Disable TPoint modeling in TheSky6

  • Remove or turn off any adaptive optics devices

  • Unplug all guider cables from the mount.

  • Unplug the mount's joystick from the Adapter Panel.

  • Physically rotate the CCD camera to orient it north up.

 

Remember, you are not "autoguiding" on the star; rather, you are recording the star's position over time. Collecting tracking data is typically less demanding than autoguiding since mount calibration is not required.

 

The resulting CCDSoft tracking log file (named "autoguider.log" since this log is normally used to record autoguiding data) allows PrecisionPEC to determine the best fit periodic error curve for your mount.

 

Here's step-by-step procedure to follow.

 

On the Paramount

  1. Unplug the autoguider cable from the Adaptor Panel and/or Instrument Panel.

  2. Unplug the joystick from the Adaptor Panel.

 

 

 

From TheSky6

  1. Launch TheSky6 Professional Edition version 6.0.0.28 or later.

  2. Click Telescope | Link | Establish to connect to the Paramount.

  3. Click Telescope | Setup and clear Enable TPoint telescope modeling option.

  4. Click Telescope | Options | PEC and clear the check mark next to the Enable command.

  5. Click Telescope | Options | ProTrack to display the ProTrack dialog box.

  6. On the ProTrack dialog box, clear the Enable Tracking Adjustements option. This will prevent ProTrack from making corrections.

  7. Click OK.

 

 

TheSky6 is now ready to control the Paramount to collect periodic error correction data. Next, make sure your camera is oriented North "up," and that CCDSoft is configured correctly to collect tracking data (and not collecting autoguiding error data).

 

Remember, you must first DISABLE AUTOGUIDING CORRECTIONS IN BOTH AXES in CCDSoft before collecting tracking data. The steps below describe how to do so.

 

From CCDSoft

  1. Launch CCDSoft version 5.00.141 or later.

  2. Click Camera | Autoguide.

  3. Click the Imager option. You can use either your autoguiding detector, or your imaging detector to autoguide. Using the larger imaging detector makes the process of acquiring a guide star easier.

  4. Click Settings.

  5. On the Drive Settings tab, click the Advanced option.

  6. VERY IMPORTANT: DISABLE AUTOGUIDING CORRECTIONS IN BOTH AXIS.

 

Clear both Yes options for Enabled X-Axis and Y-Axis during autoguiding. Turning these options off prevents CCDSoft from making corrections to the position of the guide star. See the screen capture below for details.

 

Make sure to  DISABLE AUTOGUIDING CORRECTIONS IN BOTH AXIS

by clearing the Enabled Yes options for both the X-Axis and Y-Axis.

 

  1. Click Delete 'Imager.log' to delete the existing log file. Click Yes to confirm deletion.

  2. Mark the Log Autoguiding Data To File 'Imager.log' option.

  3. Click OK.

  4. Locate and appropriate guide star (see Tips below) and then click the Autoguide button.

 

Camera Orientation Requirements

 

  • Make sure the CCD camera is oriented correctly. The camera's detector must be oriented so that telescope motion in right ascension closely corresponds to x-axis motion on the detector (see diagram below). If the detector is not oriented properly, then the maximum magnitude of the periodic error is not recorded. Note that precise orientation is not crucial; the detector should be within 5 degrees of North (or South).

 

Orientation of the detector with respect to the telescope

 

  • Always delete the existing Imager.log file (located in the CCDSoft folder) before collecting tracking data. Otherwise, new tracking data is appended to the existing log.  

 

Periodic Error Tracking Data Collection Requirements

 

  • AUTOGUIDING CORRECTIONS MUST BE DISABLED IN BOTH AXES BEFORE ACQUIRING TRACKING DATA.

  • The guide star must be a relative bright star on the west side of the meridian, near 0 degrees declination and near the meridian (within a few degrees).

  • Autoguide for at least 10 minutes (that is, for four periods of the worm).

  • Make sure to compute and record the image scale for your imaging system. It's required for the next step.

 

See Locating a Suitable Tracking Star for details.

 

 

 

 

 

 

2.

Use PrecisionPEC to Generate PEC Curve

 

Once the position of the guide star has been logged for at least 10 minutes (four periods of the worm), you're ready to generate the PEC curve to download into the Paramount's "PEC table".

 

  1. Launch PrecisionPEC.

  2. Click File | Open CCDSoft Autoguiding Log.

  3. On the Open CCDSoft Autoguiding Log dialog box, navigate to the folder that holds the autoguider log file.

 

 

  1. Select the autoguider log file and then click Open.

  2. The "raw" periodic error data is loaded from this file, and graphed on the main window. The screen capture below shows the graph of a typical autoguider log. The downward "drift" of the data along the y-axis is caused by imperfect polar alignment, and other guiding errors, and is normal.

 

 

  1. Specify the "system-specific" settings for your equipment. Enter your image scale in arcseconds per pixel. If you do not know the scale of your image, use TheSky6's Data | Image Link | Link Wizard command to compute it for you. Mark the East or West option to indicate the direction of the positive X relay direction. Click the Determine button to manually determine this direction.

  2. Click Data | Fit. After a few seconds, the Graph of Periodic Error is updated with the computed periodic error curve for your mount.

 

 

  1. Click the Final option to display the graph of the curve that will be transferred to the Paramount control system's flash RAM.

 

 

The above PEC curve is not "smooth" by design. The Final graph shows the minimum resolution for mount "moves" (approximately 0.01 arcseconds) when applying periodic error corrections. This data is saved to the control system's Flash RAM, and will be always be used to correct the mount's periodic error (provided PEC is enabled in TheSky6).

 

3.

Transfer Final PEC Curve to the Paramount

 

  1. Click Data | Send To Paramount to upload this curve into the Paramount's PEC table (that is, the curve is saved in the control system's flash RAM for permanent use).

 

After programming the PEC curve to the control system, the MKS 3000 control system must be powered off, and then on, before the new PEC table is used.

 

The MKS 3200 and MKS 4000 control systems do not need to be restarted after the PEC table is updated.

 

 

4.

Enable PEC Corrections and ProTrack Corrections

 

  1. Launch TheSky6 Professional Edition version 6.0.0.28 or later.

  2. Click Telescope | Link | Establish to connect to the Paramount.

  3. Click Telescope | Options | More Options to display the More Options dialog box.

 

 

  1. On the Periodic Error Correction tab, mark the Apply PEC Correction option and then click OK.

  2. Click Telescope | Options | PEC | Enable. Both settings (steps d. and e.) must be marked before PEC is actually enabled.

  3. If you're using ProTrack, click Telescope | Options | ProTrack to display the ProTrack dialog box. On the ProTrack dialog box, mark the Enable Tracking Adjustements option. This will enable ProTrack corrections. Click OK.

 

 

5.

If your Paramount ME uses firmware version 1.1.45 or earlier (green electronic boards), then you must turn the mount off, then on, before the PEC table can be used.

 

Paramount ME firmware version's 2.5.19 and later (red-colored electronic boards) do not require cycling the power to use the PEC table.

 

See Appendix C of the latest Paramount ME manual to determine the firmware version of your Paramount ME.

 

 

Your Paramount will now use the optimal PEC curve for the errors in your worm/gear!