What is PEMPro?

PEMPro is short for Periodic Error Management Professional. It is a Windows software application that makes it very easy to characterize and reduce the periodic error of your telescope/ mount.

What is Periodic Error and why should I care about it?

All telescope drives, including professional drives, have mechanical imperfections in the gears and worm, and the worm wheel that ultimately points the telescope.  These imperfections occur with a period determined by the rotational speed of the driving worm gear, but there can also be significant effects from other gears in the RA gear train.  If not corrected it makes taking unguided images impossible with even moderate focal length telescopes. Even auto-guided imaging is made more difficult because of periodic error. It is much better if the periodic error is corrected before the auto-guider gets a crack at it. Then guided imaging can be more accurate and produce tighter stars.

What is Periodic Error Correction?

Almost all telescope drives made for astrophotography have some sort of Periodic Error Correction (PEC) facility, even inexpensive mounts. The purpose of PEC is to compensate for the mechanical imperfections in the RA motion of the telescope caused by imperfections in the drive.  Note that some mounts have a different name for PEC such as PEM (Astro-Physics, Inc.) and SmartDrive (Meade).

Typical ways to “train” your mount’s PEC  

• Manually with cross-hair eyepiece – very tedious but can produce good results.
• With an Auto-guider – limited by seeing and the accuracy of software and hardware control. Also the time delay between autoguider image acquisition and mount movement r educes the accuracy of the corrections.
• With PEMPro – periodic error is collected over multiple cycles and modeled before being written back to the mount. Effects of seeing and delays in image acquisition are eliminated.

How PEMPro Works

The process of using PEMPro is very simple, but you will need a telescope and CCD camera that optimally provides at least 1.5 arc-seconds/pixel resolution for the best results.

1. Acquire PE Data. Details...
2. Load the PE data for analysis. Details...
3. Create a fitted PE curve to the data. Details...
4. Program the mount with the PE curve.
5. Verify PE has been corrected by acquiring PE data again.

Software required/supported by PEMPro

Required Software and System Configuration:

• Windows 98, Windows ME, Windows 2000 Professional, Windows XP, Windows XP Professional, Windows Vista and later. Windows XP, XP Professional, or Vista is recommended.
• Microsoft Windows .Net 1.1 Framework. At the time of this writing you can download it from here: http://www.microsoft.com/downloads/details.aspx?FamilyID=262D25E3-F589-4842-8157-034D1E7CF3A3&displaylang=en
• One of these CCD camera applications:
  • Diffraction Limited MaximDL/CCD v3.22, or v4.10 or later: http://www.diffractionlimited.com
  • Software Bisque CCDSoft v5.00.170 or later. http://www.bisque.com
  • AstroArt V3 with Service Pack 3, AstroArt V4, or later. http://www.msb-astroart.com
• The latest ASCOM Telescope Driver installation. http://www.ascom-standards.org

Mounts supported by PEMPro

Please click this link for a list of mounts supported by PEMPro.

PEMPro can upload PEC data directly to some mounts. You should use the procedure below if your mount is one of these types:

Astro-Physics 1200GTO with GTOCP3, 900GTO with GTOCP3, Mach1 GTO, and other mounts using the AP GTOCP3 controller

Celestron CGE, CPC, and Nextstar Mounts

Mounts with Gemini Level 4

Meade LX-200GPS and LX-200R with Firmware 2.x or later

Meade RCX-400 and MaxMount

Meade Classic 16"

Software Bisque Paramount GT1100S and ME

 

Hardware required by PEMPro

  500 MHz PIII or faster PC (2.0 GHz P4 or faster is recommended)

• 256 MB or more of RAM (512 MB or more is recommended)
• 5MB or more of Disk space
• Monitor with 1024x768 or higher resolution and 64,000 colors, 1280x1024 or higher resolution and 24-bit color recommended.
• CCD camera compatible with MaximDL or CCDSoft. No autoguider is required, the main camera is used to acquire periodic error data.
• A compatible telescope or mount (see above).

Important Note

Note: Some pictures in this help file show "PEMPro v1.50" in the title, however these pictures still apply to v1.60 and later.