| June 07.75 UT | (I-Band) m1=10.0, coma diameter=1'.1, 1'.7 tail in p.a. 280 deg. |
| June 07.74 UT | m1=10.9, coma diameter=0'.65, 0'.7 tail in p.a. 280 deg. |
| June 06.75 UT | m1=10.4, coma diameter=1'.0, 1'.3 tail in p.a. 279 deg. |
| June 04.75 UT | m1=10.5, coma diameter=0'.85, 0'.9 tail in p.a. 281 deg. |
| June 01.76 UT | m1=10.5, coma diameter=1'.3, 1'.3 tail in p.a. 274 deg. |
| May 29.75 UT | m1=11.0, coma diameter=0'.85, 1'.0 tail in p.a. 278 deg. |
| May 24.75 UT | m1=11.6, coma diameter=0'.75. |
| May 18.75 UT | m1 about 11.6, coma diameter=0'.7. |
| May 14.76 UT | The comet cannot be seen. The spot for observation was shrouded in dense fog. |
| May 8.79 UT | C/1999 S4 cannot be seen, because it was bad condition by the clouds at low altitude. |
| May 4.77 UT | The observation in the morning sky was successfully.
The unfiltered CCD magnitude was about 13.0, and the comet had a coma diameter of 0'.4. |
| Apr. 29.78 UT | The comet cannot be seen. |
| Apr. 28.79 UT | C/1999 S4 cannot be found. 12 mag stars can be detected on images. |
