98/99 Mars CMO Note (4)

1998/99 Mars CMO Note
- 04 -
from CMO #228

Distributions of the observation rates of Ak, Id, Iw, Mk, Mn, Nj and DPk in 1998/99

  @ This belongs to the series that started from the one in #118 (25 June 1992) and, as a sequel to the one in #206 p2307, treats how the individual observation rate distributed every month as the apparent diameter varied in 1998/99. This time we pick out seven observers as examples. We first take into account the cases of the CCD observers (AKUTSU and PARKER) in addition to the visual observers.
@ Instead of the apparent diameter delta (solid curve), we here feature the squared-delta (dotted curve) because its rise and decay can more appropriately fit the variation of the area of the Martian surface. The graph of the squared-delta is chosen in such a way that the integral of the graph is equal to that made by the graph of the delta -curve.
@ The bar-graphs are made by reading the data by Ns from the CMO Reports hitherto (up until mid-December 1999). The integrals of the bar-graphs are set equal to that of the delta graph.

  @ IWASAKI (Iw)'s case shows a typical one in that he observed most when the planet most approached, but was late in beginning his routine observation, and so the main peak is too high. He obtained a total number of 130 drawings this apparition, but it proved to be the least ever since he began in 1984 (when he observed 139 times; and in 1990 he obtained 400 drawings). His plain attitude was in contrast with MURAKAMI (Mk)'s when they met the white morning cloud on 26 April 1999 (reported in #227).
@ Mk made steady observations, and obtained as much as he did last observations (in 1996/97 he secured a total of 226 drawings; while this season 237 by Feb 2000). A second peak in Dec 1998/Jan 1999 was made during the time he introduced a new telescope of a 20 cm spec. The dip in Aug/Sept was caused by a bad weather common to every observer in the main islands.

@ In this point ISHADOH (Id) in Okinawa proved extraordinary: His peaks came much after opposition. Note however this is not his pattern (his peak came rather before opposition in 1996/97 as shown in #206 p2308). This apparition before and around opposition he was unhappy since his father had a severe illness and passed away. After opposition he was endowed with rather fine weather.

  @ The graph does not show the effect of the apparent declination, but the 1998/99 apparition was anticipated at first that it was more suited to devote our observation effort to the period before opposition because the planet was predicted to go down to the southern sky after opposition especially after July and most southern (down to 25°S) in October. Because of this prediction, NAKAJIMA (Nj) and one of us (MINAMI, Mn) tried to observe more intensively before opposition. Don PARKER's observation also looks on the same line: he steadily augmented his rate as the apparent diameter was growing as shown in the graph. In this respect also Id's case can be said abnormal, but partly shows that the conditions, weather and altitude in Okinawa were advantageous. In contrast, the weather in Florida might have been rather unstable after opposition because of the seasonal weather.

  @ Nj makes a first appearance in this series. He produced nearly six hundred observations with a good statistics this apparition. He enjoyed a combination with Mn, and hence his distribution looks quite similar to Mn's. A little difference is seen in June/July: This difference was apparent in the analysis of the northern white dusty clouds in June/July as noted in #226 Note (2).

@ AKUTSU (Ak) also shows up first here. The observation by photos or CCD images receives its peak at opposition, and Ak's case shows this tendency, though Ak's observation period was rather wide. PARKER (DPk) produced steadily as many images along the squared-delta curve from much before opposition to autumn as the apparent diameter increased and decreased.

  @ Another characteristic of the present apparition was, in addition to the lower altitude of the planet after opposition, the fact that the red planet began to rise up after October 1999, and since the dark markings in the southern hemisphere came to our eyes because of the tilt, we could rush again to observe lots. This tendency is typically seen in Id's case. DPk also produced several important images at the following foot of the apparition.

  @ In 2001, the planet Mars will also be quite low in the southern sky seen from the Northern Hemisphere. It will be at opposition on 13 June 2001 while its apparent declination will be down to 26.5°S (closest one week later on 20 June with delta =20.8 arcsecs). We therefore have to try to assign our observation rate more scrupulously next apparition by taking the declination into consideration.