We this time deal with the CMO observations obtained during the period from 16 January 1999 (084°Ls) to 15 February 1999 (098°Ls) where the Martian northern hemisphere experienced the summer solstice.
On 16 January the season was 084°Ls and the apparent diameter was 5.7", while they increased to 098°Ls and 6.9" respectively on 15 February 1999. The diameter increases 0.1" per day at present. The central latitude further went down from 21° N to 17°N during the period. The phase angle was from 36° downward to 35°. The apparent declination was -12° in mid-Feb.
We had rather severe weather this period (except Don PARKER (DPk) in Florida), but the observations were made as follows:
AKUTSU, Tomio (Ak) Karasuyama, Tochigi, Japan
9 CCD Images (18, 22 January; 4, 6, 8, 9, 15 February 1999)
f/60@ 32cm speculum, Teleris 2
BIVER, Nicolas (NBv) Hawaii, USA
8 Colour Drawings (17, 18, 19 Dec 1998; 14, 30 Jan; 15 February 1999)
510× 26cm speculum
GRAY, David (DGr) Kirk Merrington, Durham, UK
5 Drawings (16, 21, 22 January; 7, 8 February 1999)
350, 415, 660× 42cm Dall-Kirkham
HIGA, Yasunobu (Hg) Naha, Okinawa, Japan
12 Video Image (6, 9, 10 February 1999) 25cm speculum, Sony DCR-TRV900
HIKI, Toshiaki (Hk) Minowa, Nagano, Japan
13 Drawings (16, 26, 29, 30, 31 January; 1, 4, 11, 12, 14, 15 February 1999)
340, 360, 400× 16cm speculum
ISHADOH, Hiroshi (Id) Naha, Okinawa, Japan
15 Drawings (21, 24, 25, 26, 29 January; 6, 10, 14, 15 February 1999)
400, 530× 31cm speculum
IWASAKI, Tohru (Iw) Kitakyushu, Fukuoka, Japan
9 Drawings (6, 8, 15 February 1999) 400× 21cm speculum
MELILLO, Frank J (FMl) NY, USA
2 CCD Images (11 February 1999) 20cm SC Starlight Xpress MX-5
MINAMI, Masatsugu (Mn) Fukui, Japan
57 Drawings (17, 18, 31 January; 4, 6, 8, 14, 15 February 1999)
400, (600)× 20cm refractor*
MURAKAMI, Masami (Mk) Yokohama, Kanagawa, Japan
15 Drawings (22, 31 January; 1, 4, 5, 14, 15 February 1999)
320× 20cm Saheki speculum
NAKAJIMA, Takashi (Nj) Fukui, Japan
28 Drawings (17, 18 January; 4, 6, 8, 14, 15 February 1999)
400× 20cm refractor*
NARITA, Hiroshi (Nr) Kawasaki, Kanagawa, Japan
22 Drawings (17-21, 27, 28, 29 January; 2, 3, 5-8, 13, 14, 15 February)
400× 20cm refractor
PARKER, Donald C (DPk) Miami, FL, USA
17 CCD Images (18, 20, 29, 31 January; 2, 4, 5, 8, 9 February 1999)
f/55@ 41cm speculum equipped with Lynxx PC
QUARRA SACCO, Giovanni A (GQr) Firenze, Italia
1 CCD Image (23 January 1999) f/24@ 30cm Cass, ISIS CCD800
* Fukui City Observatory
We also received with thanks a first drawing from WARELL.
WARELL, Johan (JWr) Uppsala, Sweden
1 Drawing (11 January 1999) 330× 16cm refractor
JWr's observation was made at ω =072°W when 082°Ls. M Acidalium was shadowy near the evening terminator, and the morning limb was hazy light. It was noted that the dark fringe of the npc was not visible. The temperature recorded -15°C at the Uppsala University Observator
&nsp; We review the present observations under several headings. This time we concentrate on the observations concerning the white mists or white clouds, and refer to the dark markings only if they are related with the atmospheric phenomena.
However one month later, on 14 Feb (097°Ls) and 15 Feb (098°Ls) it turned out to be much brighter than the npc. On 15 Feb (098°Ls) at ω =280°W, Mn estimated the intensity of Hellas was 0.0~0.5 while the npc was at intensity 1.0~ 0.5, and Nj did at ω =295°W the intensity of Hellas was 0.5, while the npc was at 1.0. Hellas was seen quite light through O56 (orange), and also recognised through R60 (red).
Hellas faced to us on 14 Feb when the planet was still low but Hellas appeared conspicuous to us at ω =280°W. ISHADOH (Id) also observed 14 Feb (097°Ls) at ω =300°W that Hellas was very whitish brighter than the npc. At ω =314°W, he however notes that Hellas declined to the terminator and was less bright than the npc. MURAKAMI (Mk) started on 14 Feb from ω =316°W where he noted that Hellas was whitish bright as if protruded from the terminator. On 15 Feb (098°Ls) at ω =312°W, Id observed Hellas had much sunk though still bright but at the same time IWASAKI (Iw) first saw the bright Hellas, and succeedingly at ω =314°W, Mk recorded that Hellas was still as noticeable as the npc and the morning mist. Since the npc was uncovered and fine on 14 and 15 Feb, we can safely say that Hellas increased its brightness at a period between 085°Ls and 097°Ls.
QUARRA's CCD on 23 Jan (087°Ls) at ω =294°W During this one month, first of all AKUTSU (Ak) took CCD images on 18 Jan (085°Ls) at ω =236°W, where Hellas was still at the morning side but not so bright in blue. Going to Europe, on 23 Jan (087°Ls) at ω =294°W, Gianni QUARRA (GQr) took a pair of red and blue images, which proved Hellas was weak in red and still not so light also in blue (420nm).
However turning to America, Don PARKER (DPk) proved that Hellas was very brilliant at the beginning of February: The blue (BG12) image taken on 2 Feb (092°Ls) at ω =297°W shows very bright Hellas while the red (RG610) image does not yet, and so we have an impression that the Hellas is still covered by a haze also.
4Feb(093°Ls) at ω =272°W - ω =289°W, Hellas roundish bright though smaller in red. 8 Feb (095°Ls) at ω =243°W, the blue bright Hellas is larger than the explicit contour in red.
9 Feb (095°Ls) at ω =224°W, Hellas is not inside the disk while at ω =232°W it is large; the result indicating the position of the eastern border of the bright Hellas. All in all, the observations by DPk prove that Hellas became at maximum in brightness at around 090°Ls, as expected. Note however at that time still a thin haze covered the bright surface.
Due to the observations at Fukui on 14 & 15 Feb, the western border of the bright Hellas sank to the terminator at around ω = 330°W: Mk and Iw saw an afterimage of Hellas on 14 Feb at ω =326°W and on 15 Feb at ω =331°W respectively, while Id did not see any more Hellas at ω =324°W. We need then some calculation by taking into account the phase angle to say something.
After the completion of CMO#212, we received several impressive colour drawings from Nicolas BIVER (NBv) in which we found three drawings made in 15 Feb (098°Ls) at ω =224°W, 263°W and 285°W, describing Hellas from the morning to the noon. Hellas was brighter than the npc near the CM.
Mn observed 17 Jan (085°Ls) at ω =251°W that Utopia was brownish and fainter than Syrtis Mj; conforming to the result by Mk on 15 Jan at ω =280°W as reported in the preceding issue (at p2405). One month before on 12 Dec (069°Ls) at ω =258°W etc, Utopia appeared much darker than Syrtis Mj, and hence the change occurred during the period. The observation by Id on 14 Feb (097°Ls) at ω =300°W also proves that Utopia was fainter and obscure.
Elysium was observed whitish at the evening side on 17 Jan (085°Ls) at ω =240°W~270°W at Fukui, while Id notified that Elysium more inside was not light on 21 Jan (086°Ls) at ω=228°W. However he observed 26 Jan (089°Ls) at ω =168°W that it looked slightly light at the morning side. At the beginning of February, DPk showed a whitish light Elysium at the evening side. Especially 8 Feb (095°Ls) at ω =200°W, DPk image detected Elysium Mons which was compactly whitish. David GRAY observed a tear-drop shaped light area inside Elysium on 7 Feb (094°Ls) at ω =202°W hanging from M Cimmerium.
Ak's red image taken on 18 Jan (085°Ls) at ω =235°W shows that the Cebrenia belt is as light as Elysium. However by Int, Mn observed 17 Jan (085°Ls) at ω =241°W & 252°W that Cebrenia was not so light as Elysium. This was because Cebrenia was free from any mist, and Ak's blue image also proves the fact: In his tricolour image Cebrenia is rather reddish. DPk's images on 8 and 9 Feb (095°Ls) at around ω =230°W also show Cebrenia to be reddish.
Note the blue image of DPk on 1 Jan (078°Ls) cited at p2403 in #211 also shows the area of Cebrenia is shadowy. David GARY detected the Cebrenia belt light on 7 Feb (094°Ls) at ω =202°W / 207°W and on 8 Feb (094°Ls) at ω =166°W in Int, Wr15, Wr25 & Wr58. Incidentally the dark region to the north of Cebrenia was hazy light in Wr58.
Id isolated the whitish and roundish Olympus Mons from the evening bright Tharsis cloud on 29 Jan (090°Ls) at ω =144°W, when the apparent diameter was 7.7 arcseconds. On 8 Feb (094°Ls), DGr at Kirk Merrington detected Olympus Mons to be fairly reoundish light though duller than Elysium at the morning side.
From Japan it came into sight from around 31 Jan (091°Ls), but it appeared rather fainter. Tempe was however not lighter. M Acidalium was very detected trough O56 on 4 Feb (093°Ls) at ω =024°W, and it turned out at ω =043°W to be separated from the npc (Mn). On 5 Feb (093°Ls) at ω =053°W, Mk noticed that M Acidalium was brownish. On 6 Feb (094°Ls) at ω =046°W, Nj saw it was fainter. Id also felt it was weak at ω =081°W. On 8 Feb (095°Ls) at ω =030°W and 040°W, Mn saw it to be definite and brownish: Hyperboreus L was also seen. On 10 Feb (095°Ls), Id observed that M Acidalium was dull, but at ω =016°W isolated it from the npc. On 15 Feb (098°Ls) Mn watched how M Acidalium came from the morning limb: It remained weak but a core was seen at ω =334°W. Mk observed at the same time and estimated its intensity to be 7. DPk's excellent images on 31 Jan (091°Ls) at ω =326°W show that most part of M Acidalium was covered by the morning mist.
S Meridian was first seen this period from around 4 Feb (093°Ls) with a definite intensity. S Sabaeus was totally seen definitely on 14 and 15 Feb (098°Ls): Its western part was visible even near the morning limb. The eastern end was connected with the area of M Serpentis, but as it goes to the afternoon side S Sabaeus looked independent (looked like an independent matroos pipe) isolated from the area of Syrtis Mj because the junction area looked hazed. Deucalionis R was rather shadowy.
On 16 Jan (084°Ls) at ω =083°W, David GRAY (DGr) noted that Chryse-Xanthe was especially light near the evening terminator in Wr15. On 18 Jan (085°Ls) DPk's images all show the area of Xanthe to Tharsis to be whitish light at ω =084°W~103°W. Same on 20 Jan (086°Ls), but notable was the fact that Candor was covered but Opir was not. On 31 Jan (091°Ls) Mk observed the evening light Chryse at ω =078°W & 088°W, and similarly Mn did at ω =062°W~130°W; especially the area was remarkably white at ω =110°W with a definite contour. On 4 Feb (093°Ls) Nj observed similarly at ω =048°W~077°W. Mn checked that the mist was very thick at ω =063°W. Mk obtained a similar result at ω =082°W. On 5 Feb (093°Ls), Mk observed a mist patch at Chryse which crept up from Thymiamata at ω =053°W & ω =063°W. On 6 Feb (094°Ls), Iw observed the Thymiamata evening mist at ω =046°W. At Fukui, we observed the patch from ω =032°W, and it was connected with the Xanthe mist from around ω =076°W. Id observed at ω =081°W that the area from Chryse to Xanthe was bright. On 8 Feb (095°Ls) at Fukui we watched the evening mist patch remained and was going to creep over from around ω =351°W.
Compared with the evening Chryse mist, the morning one is much lighter and stronger because of the phase angle (presently phase angle =35°). Already this period DGr observed on 21 Jan (086°Ls) at ω =356°W that Chryse, much inside, was noticeably bright in Int, Wr15 and Wr25. The same aspect on 22 Jan at ω =353°W (in Wr58 & Wr38A). DPk took the CCDs on 29 Jan (090°Ls) at ω =339°W & 349°W where the morning Chryse is thickly white. HIGA (Hg) at Okinawa started VTR on 6 Feb (093°Ls) from ω =039°W to ω =078°W: Tharsis is bright in the morning; and at ω =069°W it looks to consist of two white patches. At Fukui Mn felt the limb area was especially stronger during the period ω =032°W~ω =051°W. On 8 Feb (095°Ls), Mn observed that Chryse was whitish bright near the morning limb at ω =341°W, 351°W and 001°W: the result was similar to the one obtained previously on 4 Jan (076°Ls) (already reported). See another item below where Nj's intensity estimate is shown at ω =006°W. On 9 Feb (095°Ls), Hg took VTR at ω =011°W~051°W where Chryse-Xanthe is bright. Ak's images on the day at ω =023°W & ω =041°W also show the morning light area near the limb. The image of Hg on 10 Feb (095°Ls) at ω =004°W also show the same aspect as on 9 Feb. On 14 Feb (097°Ls), the morning Chryse mist was seen from ω =304°W (Mn). Id felt it strong at ω =314°W, 324°W and 343°W. Mn saw it very definite at ω =338°W, while Mk felt it strong at ω =326°W. Similarly on 15 Feb (098°Ls). Iw and Mk checked it at ω =322°W and ω =324°W respectively.
On 21 Jan (086°Ls) at ω =356°W, DGr was struck by the brightness of the southern Noachis to the south of M Erythraeum through Wr25. The same scene was seen also on 22 Jan at ω =353~356°W in Wr58 and Wr38A: Seeing was II-III. Independently Mn observed on 8 Feb(094°Ls) at ω =010°W that the evening Noachis was slightly light. On 14 Feb (097°Ls) Mn watched the morning Noachis to be dull light at ω =314°W, and on 15 Feb (098°Ls) he saw it to be hazy at ω =319°W and 334°W. Mk also observed that the southern Noachis has a lighter hazy part on 14 Feb at ω =316°W and on 15 Feb at ω =314°W & 324°W.
Evening Libya mist:
This mist seemed to come up toward Libya from the area of Elysium. On 14 Feb (097°Ls) at ω =304°W & 314°W, Mn observed that the Libya mist showed a thick core near the terminator. Mk judged at ω =326°W that it invaded Syrtis Mj. On 15 Feb (098°Ls) Mn observed that the core was clear preceding Syrtis Mj at ω =309°W but at ω =319°W it invaded the latter. Mk observed that at ω =324°W Syrtis Mj started to be completely covered by the mist. Iw considered that at ω =312°W and 322°W Syrtis Mj was invaded by the Libya mist. The Libya mist goes up to Aeria and is gradually connected with Thymiamata-Chryse evening mist. Note as previously stated, the southern part of Syrtis Mj is scarcely covered by the mist and remains dark to the terminator.
The EB mist:
The long-lying mist along the Equatorial Band is seen on the blue image by Ak taken on 18 Jan (085°Ls) at ω =236°W, and also on the images by DPk on 31 Jan (091°Ls) at ω =326°W from the Libya to the west. Mk detected a thin ebm on 4 Feb (093°Ls) at ω =082°W where the morning side was thicker. Mn also observed it weakly on 6 Feb (094°Ls) at ω =032°W~051°W. Similar on 8 Feb (095°Ls) at ω =010°W~050°W. Nj on the same day saw it at ω =006°W along the line 10°N. The Video Image by Hg on 10 Feb (095°Ls) at ω =004°W rather clearly shows the ebm. Id also detected it slightly later by naked eye at ω =006°W where the evening patch was thicker.
The npc was definite. Hyperboreus L was seen, but notable was the fact that when S Sabaeus was near the CM, the npc showed no dark fringe. Iw also made a similar comment on 15 Feb. The inside of the npc region had a light and shade.
We cite partially here Nj's intensity estimates made on 8 Feb (095°Ls) at ω =006°W: the npc 1.5, morning Chryse 2, Aeria 3, Noachis area 2.5, M Acidalium 7, S Sabaeus 6.5, S Meridiani 7, Aram 3, Utopia 6, etc .
On the other hand Mk also made intensity estimation on several occasions, and we here introduce his result as an example made on 14 Feb (097°Ls) at ω =346°W: the npc 2, Libya evening mist 3, Chryse morning 2, the s-top Noachis 4, ebm at the CM 4, the desert 5, M Acidalium 7, S Meridiani 8, the circumpolar region 6, etc .
David GRAY at Kirk Merrington experienced a temperature of - 6°C (on 8 Feb) and was quite discouraged, combined with a brisk north wind, to frequently handle the filters. HIKI at the Ina Valley has frequently experienced - 6°C, and on 4 Feb GMT the temperature went down to - 12°C, while at Yokohama where MURAKAMI observes they had only 0°C on the same night. The same morning (of 5 Feb JST), we (NAKAJIMA and Mn) at Fukui also felt the lowest temperature of - 4.6°C (reported the next day from the Meteorological Observatory). It still snows here at Fukui.