December 13, 1999 02:15 UT
Instrument: 10-inch Starfinder

Apparent diameter: 45."1
Sys II CM: 206°
Sys I CM: 82°

The sketch at left captures the view at 388X in my 10-inch Starfinder Newtonian. I am able to resolve Callisto and Europa as disks for extended periods at 388X. The 80A and 23A Wratten color filters, and the neutral density Moon filter enhance a variety of low contrast features.

The North Equatorial Belt (NEB) features several impressive festoons extending from its southern edge to a broad, prominent Equatorial Belt (EB). Typically, the EB appears as a thin line popping in-and-out of view during moments of "better than lousy" seeing. I'd estimate the thickness of the EB to be around 1" and this seems broad to me. The 80A light blue filter really brings out the EB.

Another testament of the good seeing is the visibility of a festoon visible along the preceding horizon. This festoon tip appears 3" long and connects to the EB. The NEB features four festoons along the Earth-facing section. Two straddle the central meridian (CM). One precedes the CM by roughly 5° and angles sharply into the Equatorial Zone (EZ). It abruptly changes direction halfway to the EB, assuming a shallow trajectory toward the EB, and connects a third of the way toward the following limb. Immediately following the CM, a broad-based festoon dips into the EZ and intersects with another festoon. Additionally, there are festoons visible along the NEB about 5" inside each limb.

The swells and dips along NEB's northern border undulate like a roller coaster track. One swell almost closes the gap between the NEB and the North Temperate Belt (NTB). The NTB appears the darkest of the major belts. The North North Temperate Belt (NNTB) is narrow and crisp. A thin section of belt immediately to the north is visible along the CM. The Jovian atmosphere takes on a slightly grey hue at the NNTB. This hue becomes more dense about 40% of the way toward the pole. This subtle change in contrast coincides with the southern border of the North Polar Region.

The South Equatorial Belt (SEB) features a narrow northern edge, less than 1" thick, a 4" wide southern section and a narrow, off-white gap between the two. This narrow gap broadens when approaching the preceding limb. This is presumably the beginnings of the region of whitish disturbances that follow the Great Red Spot (GRS), giving this region of the SEB a much fainter appearance than the section preceding the GRS. A 3" wide South Tropical Zone (STrZ) separates the SEB from the South Temperate Belt (STB). The STB appears quite thin and another thin belt is visible barely 2" south. This southerly belt is visible from the preceding limb to the CM where it appears to join the STB. I'm thinking these are northern and southern sections of the STB. The STB is separated from the South South Temperate Belt (SSTB) by a 5" wide South Temperate Zone (STZ). This zone appears more dense preceding the CM. The South Polar Region (SPR) shows a heavy grey tone which lightens about halfway to the SSTB.

This is probably as good a view of Jupiter as I've had this season. I'm interested in seeing how things have developed in the vicinity of the GRS since my last peek at that area more than two months ago. Hopefully, I'll be able to endure another observing session or two this "cold" northern Arizona winter.

Jupiter September 30, 1999


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