Director: K. Horikawa, Secretary: Y. Iga
As the opposition of this apparition was near at hand, Jupiter was in good period for observation. The poorest condition of this winter had greatly recovered, and we often had good seeing in March. This month, we have received observations listed below. In addition, a series of maps and a GIF animation which showed the collision of SEBs dark spots with RS in January-February was sent from Einaga, and a map made from images in February was sent from Yunoki.
| Observer | Location | Telescope | Images/Drawings | |
|---|---|---|---|---|
| Adachi, Makoto | (Otsu, Japan) | 31cm Refl. | 4 | drawings |
| Einaga, Hideo | (Hyogo, Japan) | 25cm Refl. | 73 | images, 5 maps |
| Fukui, Hideto | (Shizuoka, Japan) | 25cm Refl. | 8 | images |
| Hatanaka, Akitoshi | (Mie, Japan) | 40cm Refl. | 10 | images |
| Horikawa, Kuniaki | (Yokohama, Japan) | 16cm Refl. | 21 | drawings, 6 images |
| Ikemura, Toshihiko | (Nagoya, Japan) | 31cm Refl. | 15 | images |
| Mishina, Toshiroh | (Yokohama, Japan) | 20cm Refl. | 9 | images |
| Miyazaki, Isao | (Okinawa, Japan) | 40cm Refl. | 17 | images |
| Nakai, Kenji | (Hiroshima, Japan) | 25cm SCT | 2 | images |
| Narita, Hiroshi | (Kawasaki, Japan) | 20cm Refr. | 8 | drawings |
| Pellier, Christophe | (France) | 21cm MCT | 5 | images |
| Takimoto, Ikuo | (Kagawa, Japan) | 31cm Refl. | 50 | images |
| Yoneyama, Seiichi | (Yokohama, Japan) | 20cm Refl. | 7 | images |
| Yunoki, Kenkichi | (Osaka, Japan) | 20cm Refl. | 135 | images, 1 animation |
| Tomita, Yasuaki | (Gunma, Japan) | 25cm Refl. | 1 | image |
The bridge connecting RS with SEB formed in the last month had developed into distinct arch. And dark streak emerged from its p. end to reach dark ring at about II: 60 deg., extending along SEBs edge. Whole aspect of the region was similar to RS Hollow, but strongly reddish RS could clearly be seen inside. It seems that dark arch was formed caused by collision of SEBs jetstream spots with RS. According to Einaga's maps, three or four spots reached RS one after another since January, and they distorted to disappear running round north edge of the Hollow. The collision of dark spots had stopped in March, leaving isolated large dark ring at about II: 60 deg. But it is possible that other collisions take place in the near future, because there were many humps on SEBs edge between II:200 and II:300 deg. The longitude of RS was II:101.8 deg. (Mar. 31, Einaga).
BA was at II:342.1 deg. (Mar. 19, Miyazaki). Since surrounding feature became fainter than last month, contrast of BA was somewhat lower. An isolate dark spot in STrZ was conspicuous to the north of BA. Though it was almost stationary relative to System II, its aspect was a solid spot unlike dark ring at II:60 deg. Dark STB segment was seen between BA and about II:60 deg., following which it was connected with SSTB by oblique component. In other longitude, STB was faded away remaining faint north component, this month, however, tiny dark spots were observed on STBn preceding BA. They were prograding at -3 deg./day, which indicated that they were typical STBn jetstream spots.
EZ was slightly yellowish in northern half, within which festoons were faint, bordered by fragmentary EB. Some white rift activities were seen in NEB, but no one had developed on the grand scale. There were four barges and five portholes in northern NEB. On NNTBs edge, high resolution images showed tiny dark spots, which were NNTBs jetstream spots, like those observed in previous apparition, and rapidly prograding at about -2.9 deg./day.
Ikemura obtained three images at methane absouption band. Interestingly, NTB was a intense belt at NH4 band, though it was absent in all longitudes at visible wavelength, and NEB also kept original width without broadening. This suggests that apparent change of visible albedo may not affect cloud structures that form belts and zones.
Saturn passed stationary on Mar. 22, turning into prograding motion. This month, we have received observations listed below.
| Observer | Location | Telescope | Images/Drawings | |
|---|---|---|---|---|
| Akutsu, Hiroaki | (Hokkaido, Japan) | 28cm Refl. | 1 | image |
| Einaga, Hideo | (Hyogo, Japan) | 25cm Refl. | 40 | images |
| Fukui, Hideto | (Shizuoka, Japan) | 25cm Refl. | 22 | images |
| Hatanaka, Akitoshi | (Mie, Japan) | 40cm Refl. | 22 | images |
| Ikemura, Toshihiko | (Nagoya, Japan) | 31cm Refl. | 4 | images |
| Nakai, Kenji | (Hiroshima, Japan) | 25cm SCT | 3 | images |
| Pellier, Christophe | (France) | 21cm MCT | 22 | images |
| Takimoto, Ikuo | (Kagawa, Japan) | 31cm Refl. | 50 | images |
| Yoneyama, Seiichi | (Yokohama, Japan) | 20cm Refl. | 2 | images |
| Yunoki, Kenkichi | (Osaka, Japan) | 20cm Refl. | 85 | images, 2 animations |
Yunoki's images taken on Mar. 6 and 7 showed white spot in SEB at about III:200 deg., and irregular faint shadings could be seen preceding and following the spot. Also, in infrared image on Mar. 18 by Pellier, there were two white spots in SEBZ at about III:90 deg. and 110 deg., and adjacent SEBs was irregulary wavy. It indicates that activity in this region was kept on going.
In higher latitude, while SSTZ reddening was noticed, there was an indication of change within SPR. Until January, SPR was uniformly dark with dark-green tint, but this month, center part of SPR was lighter than its edge. Yunoki compared luminosities of his own images taken in January and March, and confirmed that the region around south pole really became lighter.
(April 12, K. Horikawa)