Director: K. Horikawa, Secretary: Y. Iga
Two months have passed since solar conjunction, and Jupiter was seen in southeast sky at dawn. The altitude of Jupiter was increasing very slowly, since sunrise became early more and more. This month, we received observations listed below.
| Observer | Location | Telescope | Images/Drawings | |
|---|---|---|---|---|
| Akutsu, Tomio | (Philippines) | 35cm SCT | 9 | images |
| Carvalho, Fabio | (Brazil) | 25cm Refl. | 9 | images |
| Einaga, Hideo | (Hyogo, Japan) | 30cm Refl. | 1 | image |
| Kumamori, Teruaki | (Osaka, Japan) | 20cm Refl. | 3 | images |
| Fukui, Hideto | (Shizuoka, Japan) | 35cm SCT. | 2 | images |
| Horikawa, Kuniaki | (Yokohama, Japan) | 16cm Refl. | 4 | drawings |
The South Tropical Disturbance (STrD) has not been observed yet, though remarkable activity of the circulating current was seen there last apparition. A dark column in STrZ like a festoon (II:240.0 deg.) in Kumamori's image on Feb.21 might be STrD-1, but it seemed that it was not a dark column but an anticyclonic dark spot according to high resolution images. Also, another distinct anticyclonic spot was observed at II:174.2 (Feb. 28, Kumamori). It seemed to be a trace of STrD-2, because its longitude was close to that of STrD-2 in previous apparition. On STBn around both spots, there were no spots which suggested the circulating current. When a suspicious marking like dark column is observed in STrZ, it is difficult to determine if it is a STrD or not, without any evidence suggesting an existence of the circulating current.
SEBs had many projections, and was filled with prenty of dark rings according to Carvalho's images. But it is unknown whether these spots were retrograding with SEBs jetstream. Dark spots became fewer following II: 20 deg., and latitude of SEBs edge was somewhat lower. SEB was dark belt divided into two components by light SEBZ all round the planet. The color was different between the components. The south component was bluish, while the north component was reddish.
RS was observed as a distinct oval with clear outline and dark core at its center at II:122.8 deg. (Feb. 28, Carvalho). It was strongly reddish, so it seemed that it was not affected by SEBs activity, as in previous apparition. Following RS, SEB was very turbulent with irregular spots. It is unknown whether it was an aftermath of SEB Revival or reappearance of post-GRS disturbance. BA was indistinct at II:184.4 deg. (Feb, 28, Kumamori). It was followed by STB dark segment, which became shorter than that in last apparition. A lot of tiny reddish dark spots were seen along narrow faint STBn preceding RS. It was not confirmed that these were rapidly prograding with STBn jetstream, but these may be formed from broadened STBn which was observed in late stage of last apparition.
EZ was bright without any traces of darkening which was seen in the first half of last apparition. EB and festoons were clear, but they were somewhat fainter than those in previous apparition. On NEBn edge, alternate patterns of barge and notch were developed in wide range of longitude. Since such patterns frequently appear when NEBn edge is retreating, it is expected that NEB will become narrow in this apparition. NTB was distinct all round the planet as a broad belt. It was double in high-resolution images, and NTBs was darker and reddish.
Saturn was at opposition in Leo on Feb. 24, and was in good period for observation. This month, we received observations listed below.
| Observer | Location | Telescope | Images/Drawings | |
|---|---|---|---|---|
| Akutsu, Hiroaki | (Hokkaido, Japan) | 28cm Refl. | 4 | images |
| Akutsu, Tomio | (Philippines) | 35cm SCT | 4 | images |
| Fukui, Hideto | (Shizuoka, Japan) | 35cm SCT. | 1 | image |
| Go, Christopher | (Philippines) | 28cm SCT | 1 | image |
| Ikemura, Toshihiko | (Nagoya, Japan) | 30cm/38cm Refl. | 6 | images |
| Kazemoto, Akira | (Kyoto, Japan) | 31cm Refl. | 7 | images |
| Kumamori, Teruaki | (Osaka, Japan) | 20cm Refl. | 9 | images, 1 animation |
| Mishina, Toshiroh | (Yokohama, Japan) | 20cm Refl. | 1 | image |
| Nakai, Kenji | (Hiroshima, Japan) | 25cm MCT | 1 | image |
| Takimoto, Ikuo | (Kagawa, Japan) | 31cm Refl. | 3 | images |
| Tomita, Yasuaki | (Gunma, Japan) | 25cm Refl. | 1 | image |
| Yoneyama, Seiichi | (Yokohama, Japan) | 20cm Refl. | 6 | images |
| Yunoki, Kenkichi | (Osaka, Japan) | 26cm Refl. | 24 | images |
White spot on STBn edge was still visible. It was clearly seen in images on Feb. 19 by Kazemoto amd Ikemura at III:298.2 deg., -41.6 deg. in latitude, having somewhat retrograded from January. Because it was at III:272.2 deg. when it was first observed by Go in last December, its drift rate is +0.3 deg./day which is much smaller than former spot in 2006 (+0.7 deg./day). While the lifetime of former spot was about two month and a half, this spot will survive for three months soon. The heyday of the spot may have already passed, since it was diffused and became somewhat larger from last month. But it was still bright, so it could be observed for a while. By the way, Tomio Akutsu observed a white spot in SEB at III:146.3 deg. on Feb. 25. But it would be difficult to track the spot, since it was very low contrast.
Yunoki's image on Feb. 10 showed dark and white spots in high northern latitude. These were Tethys and its shadow in transit over Saturnian disk. It is rare phenomenon which can be seen when tilt of the ring is small. Because transits by larger satellites will often take place from now on, observers must be careful not to mistake it for a white spot or dark spot on the disk. Every observer's images indicated that the ring was brighter than usual this month. This was due to the opposition effect which was always observed in recent apparitions.
(March 14, K. Horikawa)
(Translated on April 22)