Analysis of Tracking Drift of a Telescope Mount

C2A integrates a tool to analyse and to graphically represent the tracking drift of a telescope mount. In the present version,  C2A loads files produced by the Iris software (see, Guidemaster (, CCDSoft ( and MaxIm DL ( To use this tool, go to the Telescope menu and click the command Tracking drift analysis.

Getting tracking drift of a telescope is usually done like this:

Iris then generates 2 files ending with the characters "_x.dat" and "_y.dat" respectively (in the working directory specified in the Settings... dialogue box of the File menu) which contains all the drift of the star observed during the observation period (the drift is in pixels). It is these files which must be loaded in C2A (using the Load button). Just load one of these files and C2A will immediately recognise the other.

The screenshot below shows the tracking drift analysis window. To get information on one of the components of the window, left-click on it:

Once the files are loaded, you must fill in the box Arc seconds per pixel... so that the scale of the graph correctly shows drift in arc seconds. You can then “zoom in” segments of the curve by left-clicking on them (the right mouse button works in a similar way, but “zooms out”). You can also use the "+" (zoom in), "-" (zoom out) buttons and "G" (global view). The "Copy" button allows you to copy the current graph view onto the Windows clipboard (with the possibility of  pasting it into another document).

The button Show FFT... lets you display the Fourier transform of the data series loaded in the tracking drift analysis window. This graph shows the main periods present in the data series. The screen shot below shows, for example, the FFT curve of the periodic error shown above. It readily identifies the main frequency as about 10 minutes 21 seconds.

An example of datfiles produced with Iris is included with C2A (files Iris_data_x.dat et Iris_data_y.dat).

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