We investigate the long-term spatial drift of the center and the temporal variation of the shutter delay time map of Y4KCam mounted on the CTIO 1.0 m telescope. We have collected shutter delay time maps over eight years as a part of our long-term survey program. We find that the center of the shutter delay time map can drift up to 450 μm, equivalent to  30 pixels, on the CCD. This effect can result in a small amount of error in integration time without the proper shutter delay time correction, but it does not appear to cause any significant problems in photometric measurements. We obtain a mean shutter delay time of 69.1 ± 0.8 ms and find no temporal variation of the shutter delay time of Y4KCam over eight years, indicative of the mechanical stability of the shutter. We suggest that using a master shutter delay time correction frame would be sufficient to achieve high precision photometry, which does not exceed photometric errors ~ 1.7 mmag across the CCD frame for exposure times longer than 1 s.

Abstract
1. INTRODUCTION
2. THE PRONTOR MAGNETIC E/100 SHUTTER
3. DATA AND REDUCTIONS
4. RESULTS
    4.1. The Drift of Center of the Shutter Delay Time Map
    4.2. Temporal Variation of the Shutter Delay Time
5. SUMMARY
REFERENCES

• Jae-Woo Lee(Department of Physics and Astronomy, Sejong University) Corresponding author
• Richard Pogge(Department of Astronomy, Ohio State University)