1. The pointing calibration of the WFCTA tracking system
Lingling Ma
IHEP

2. Outline Introduction of the WFCTA telescope
The method of the pointing direction calibration
Night sky background
Method ---- the guide of bright stars
The results of the calibration
Accuracy
The pointing error of the tracking system
Conclusions

3. Wild Field Cherenkov Telescope Array.
Field of view
256 PMTs (1°×1°)
14°×16°
It takes a star 40~50minites to pass through the FOV
Step-tracking system
How to estimate the pointing accuracy
How to estimate the pointing error of the tracking system
Trace of crab

4. Method ----Night sky background
The diffuse night sky background
The star light
A bright star pass through the FOV of a PMT

5. Method ----The guide of bright stars
TD1 catalog
Search the trace of the brightest star on the camera by the PMTs with the highest signal
Fit the trace to get the pointing direction of telescope
Tune the pointing direction by other bright stars
Compare the pointing direction with the one given by the tracking system to check the accuracy and the systematics

6. Results ----accuracy
The differences between the positions of the bright stars and the one observed by the telescope in local coordinates are defined as the accuracy of the calibration.

7. Accuracy
Azimuth
Elevation
The accuracy is better than 0.1°

8. The pointing error
Delta-degree
Delta-degree

9. Conclusions The accuracy of the calibration is better than 0.1°
The pointing error of the tracking system
Azimuth: 1.5°
Elevation: 1.2°
More data is expected