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iOptron iEQ45 Review

iOptron iEQ45 Periodic Error

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iOptron IEQ45 Periodic Error

iOptron IEQ45The following analysis of the periodic error of my iOptron IEQ45 was undertaken using PEMPro version 2 with the following telescope/camera setup

Telescope - Takahashi FSQ016ED
Imaging Camera - FLI ML8300

The focal length of the FSQ106 is 530mm and the pixel size of the ML8300 is 5.4 microns. The image scale is therefore 2.1 arc seconds per pixel.


The FSQ106/ML8300 combination weighs 10kg, which is half of the specified maximum load capacity for the IEQ45.

In order to obtain a good average of the periodic error, 1229 samples were collected over eleven complate worm cycles.

When viewing the graphs, please ignore the figures in the worm cycles, total time and current worm phase boxes. These are incorrect due to the fact that the graphs were recreated in PemPro at a later date for the purpose of creating the screen-shot images.

The first graph shows the data collected during the recording stage. The mount's PEC function was turned off during recording.

iOptron IEQ45 Periodic Error Recording Stage

The second graph shows the periodic error curve produced by PEMPro from the data collected during the recording stage. As you can see from the image, the periodic error was determined to be 31.47 arc seconds peak to peak.

iOptron IEQ45 Periodic Error Curve

In order to check the effectiveness of programming the mount, I turned on the mount's PEC playback option and created a further PE curve in PEMPro. The following graph shows the actual recording session with PEC enabled.

ioptron ieq45 with PEC enabled

The final graph shows the PE curve with the mount's PEC function set to play. As you can see, the periodic error has been reduced from 31.47 arc secs peak to peak to 6.01 arc secs peak to peak.

ioptron ieq45 periodic error curve with PEC enabled

There are basically three ways of programming the PE data to the mount. First, some mounts, such as Astro-Physics and those running Gemini 4, have the capability to upload the PE data direct. Second, some mounts have the capability to record the PE data via the ASCOM driver. This method entails setting PemPro to playback the PE curev to the mount and for the mount to be set to record. Third, for mounts without the capability to programmed by either of the first two options, the mount can be programmed via the autoguider port. For this method, PemPro is set to playback the PE curve and acts like a virtual autoguider. The mount is set to record and receives the PE corrections via the autoguider port.

In the case of the iOptron iEQ45, the mount cannot be programmed direct, but should be able to be programmed via the ASCOM driver. I initially had difficulty in getting the mount to record the PE data using this method, but thanks to the help of both Ray Gralak and iOptron Technical support, eventually did manage to do so by using the following settings in PEMPro. Please note that the "Advanced Configuration" box is checked with the Pulse Modulo set to 100 msecs and the Pulse Phase set to -500.

iOptron iEQ45 PemPro Settings

As far as I am aware, PemPRO is the only software available that will program the periodic error correction data to the mount. However, there are a number of freeware programs available for measuring periodic error, including EQAlign, PECPrep and MetaGuide.