The 9.3-mag. star PPM 94539 will be occulted by the asteroid 275 Sapientia Wednesday night-Thursday morning, March 18-19, from north of Calgary, Alberta to north of Minneapolis, Minn., according to Hipparcos and ACT-relative astrometry at the Table Mountain and U. S. Naval (Flagstaff, Ariz.) Obervatories obtained 1997 Nov. 27 to 1998 March 5. This path is 4 path-widths north of the path shown on p. 86 of the Feb. issue of Sky and Telescope, and the time correction from that path is only 0.4 minutes late. The path uncertainty is probably better than +/-one path-width and the time should be accurate to a few tenths of a minute. A more extensive description of the path is that it crosses the Alaska Peninsula and just south of Kodiak Is. at 6:11 U.T. of March 19 U.T.; over Ketchikan, Alaska at 6:12 UT; north of Calgary, Alberta at 6:13.4 UT; south of Regina, Sask. at 6:13.7 UT; north of Minneapois, Minn. at 6:14.0 UT (star alt. 13 deg.); over Oshkosh, Wisc. at 6:14.1 UT (alt. 9 deg.); and over Grand Rapids, Mich. at 6:14.2 UT (alt. 5 deg.). More detailed path information is given below. A map of the new path may be generated this afternoon and placed on IOTA's Web site at http://www.anomalies.com/iota/splash.htm in the upcoming events section a few hours before the occultation, and possibly a little sooner at IOTA's other site at http://www.sky.net/~robinson/iotandx.htm.
The star is easy to find, being only 0.4 deg. west of the 3rd-mag. star zeta Tauri and about a deg. south of the Crab Nebula; PPM 94539's J2000 position is R.A. 5h 35m 53.8s, Dec. +21 deg. 02' 58". A finder chart showing the star is in the upcoming events section of the anomalies.com Web site mentioned above; in the table, click on "PPM 94539" to get the chart. The chart also has a small world view showing the nominal (uncorrected) path; ignore that path, which is superseded by the information given here.
There is some ambiguity about the prediction, since the R.A. and Dec. residuals of Sapientia show some linear trends over the 3-month span of accurate USNO and TMO observations, but none of those observations are very close to the March 19th date of the occultation. If an average of all of the observations is used rather than the extrapolation of the linear trends that I have used here, the path would be almost another path-width farther north; a detailed prediction comparison is given at the end of this message. Perhaps confirming this more northern averaged prediction are recent (March 17th) ACT-relative observations of Sapientia by Gordon Garradd in Australia; they are in almost exact agreement with the average. However, the linear trends in the other data are strong, and with the +21 deg. dec. of the star, Garradd's southern latitude is a disadvantage (star relatively low in the north when near his meridian) and his focal length is smaller than the TMO and USNO telescopes. Nevertheless, a north shift from my detailed predictions below is probably more likely than a south shift. Observers anywhere within the +/-1 path-width uncertainty zone are encouraged to attempt observations if the weather permits.
Occultation and path details are given below.
OCCULTATION OF 9.35-MAG. PPM 94539, SPECTRAL TYPE B8) BY 275 Sapientia
ON 1998 MAR 19
IN VISUAL, MAG. DROP AT DISAPPEARANCE= 4.52
DIAMETER= 103. KM = 0.059 SECONDS OF ARC, CENTRAL OCCN. = 5.558 SECONDS
This diameter is from an occultation of a 6.8-mag. star by Sapientia
observed on 1985 April 15 by Phil Nicholson, Ithaca, NY and by me at
Duluth, MN; the circular determination was 103 +/-12 km.
70-PERCENT-SUNLIT WANING MOON 160.0 DEGREES AWAY, SUN 85.93 DEGREES AWAY
Sapientia 2.394004 A.U. FROM EARTH, PHASE ANGLE= 23.1DEGREES
CENTER PATH IS ABOUT 124. KM WIDE AT THE COORDINATES LISTED BELOW
UNIV. TIME Sapientia SUN MOON
LONGITUDE LATITUDE H M S ALT. AZI. ALT. AZI. ALT.
171.39 W 56.60 6 10 46.3 53.0 201.9 -5.6 277.5 -41.7
165.42 W 56.83 6 11 5.2 51.3 210.7 -8.9 282.6 -39.0
159.41 W 56.89 6 11 23.7 49.3 219.1 -12.1 287.9 -36.2
153.40 W 56.78 6 11 41.7 47.2 227.0 -15.2 293.3 -33.3
135.79 W 55.50 6 12 31.2 39.5 247.8 -24.3 309.6 -24.1
132.96 W 55.15 6 12 38.7 38.1 250.9 -25.8 312.3 -22.5
130.17 W 54.77 6 12 46.0 36.6 253.9 -27.2 315.0 -20.9
127.42 W 54.35 6 12 53.1 35.2 256.7 -28.6 317.8 -19.3
124.71 W 53.91 6 12 59.9 33.7 259.5 -30.0 320.5 -17.7
122.04 W 53.43 6 13 6.4 32.2 262.1 -31.4 323.2 -16.1
119.42 W 52.93 6 13 12.7 30.7 264.7 -32.7 326.0 -14.4
116.85 W 52.39 6 13 18.7 29.2 267.1 -34.0 328.7 -12.8
114.32 W 51.84 6 13 24.4 27.6 269.4 -35.3 331.5 -11.2
111.83 W 51.26 6 13 29.8 26.1 271.7 -36.5 334.3 -9.5
109.39 W 50.65 6 13 35.0 24.5 273.8 -37.7 337.1 -7.9
107.00 W 50.03 6 13 39.8 22.9 275.9 -38.8 339.9 -6.2
104.65 W 49.38 6 13 44.3 21.3 277.9 -39.9 342.7 -4.6
102.33 W 48.72 6 13 48.6 19.7 279.8 -41.0 345.6 -2.9
100.06 W 48.04 6 13 52.5 18.1 281.7 -42.0 348.4 -1.2
97.83 W 47.35 6 13 56.0 16.4 283.4 -42.9 351.4 0.4
95.64 W 46.65 6 13 59.3 14.8 285.1 -43.8 354.3 2.1
93.48 W 45.93 6 14 2.2 13.2 286.8 -44.7 357.3 3.8
91.36 W 45.20 6 14 4.8 11.5 288.4 -45.4 0.3 5.4
89.27 W 44.45 6 14 7.0 9.9 289.9 -46.1 3.3 7.1
87.21 W 43.71 6 14 8.9 8.2 291.3 -46.7 6.4 8.7
85.18 W 42.95 6 14 10.5 6.6 292.8 -47.3 9.5 10.4
83.18 W 42.18 6 14 11.7 4.9 294.1 -47.8 12.5 12.0
TRACK 0 CENTER FOR 275 Sapientia SAO 0 DATE 1998 MAR 19
W. LONG. LAT. W. LONG. LAT. W. LONG. LAT. W. LONG. LAT.
130.000 54 44.6 117.000 52 25.6 104.000 49 12.2 91.000 45 4.2
129.000 54 35.8 116.000 52 12.6 103.000 48 55.0 90.000 44 43.0
128.000 54 26.7 115.000 51 59.4 102.000 48 37.5 89.000 44 21.5
127.000 54 17.2 114.000 51 45.8 101.000 48 19.7 88.000 43 59.7
126.000 54 7.5 113.000 51 31.9 100.000 48 1.5 87.000 43 37.7
125.000 53 57.4 112.000 51 17.7 99.000 47 43.1 86.000 43 15.4
124.000 53 47.0 111.000 51 3.2 98.000 47 24.3 85.000 42 52.8
123.000 53 36.4 110.000 50 48.3 97.000 47 5.2 84.000 42 29.9
122.000 53 25.4 109.000 50 33.1 96.000 46 45.8 83.000 42 6.8
121.000 53 14.0 108.000 50 17.6 95.000 46 26.1 82.000 41 43.5
120.000 53 2.4 107.000 50 1.7 94.000 46 6.1
119.000 52 50.4 106.000 49 45.5 93.000 45 45.8
118.000 52 38.2 105.000 49 29.0 92.000 45 25.1
h m s o o
AT U.T. 6 13 0, W. LONG.= 124.654, LAT.= 53.898
AT U.T. 6 13 20, W. LONG.= 116.278, LAT.= 52.271
AT U.T. 6 13 40, W. LONG.= 106.907, LAT.= 50.003
AT U.T. 6 14 0, W. LONG.= 95.125, LAT.= 46.476
Northern limit if path shifts 1 path-width north (TRACK 83 NORTH)
W. LONG. LAT. W. LONG. LAT. W. LONG. LAT. W. LONG. LAT.
129.000 56 14.5 116.000 53 54.2 103.000 50 39.7 90.000 46 30.3
128.000 56 5.6 115.000 53 41.2 102.000 50 22.4 89.000 46 9.0
127.000 55 56.3 114.000 53 27.9 101.000 50 4.8 88.000 45 47.4
126.000 55 46.8 113.000 53 14.3 100.000 49 46.9 87.000 45 25.5
125.000 55 37.0 112.000 53 0.3 99.000 49 28.7 86.000 45 3.3
124.000 55 26.8 111.000 52 46.0 98.000 49 10.1 85.000 44 40.8
123.000 55 16.3 110.000 52 31.3 97.000 48 51.2 84.000 44 18.1
122.000 55 5.6 109.000 52 16.4 96.000 48 32.0 83.000 43 55.1
121.000 54 54.5 108.000 52 1.1 95.000 48 12.5 82.000 43 31.9
120.000 54 43.1 107.000 51 45.5 94.000 47 52.7 81.000 43 8.4
119.000 54 31.3 106.000 51 29.5 93.000 47 32.6
118.000 54 19.3 105.000 51 13.2 92.000 47 12.1
117.000 54 6.9 104.000 50 56.6 91.000 46 51.4
Southern limit if path shifts 1 path-width south (TRACK 83 SOUTH)
W. LONG. LAT. W. LONG. LAT. W. LONG. LAT. W. LONG. LAT.
130.000 53 8.0 118.000 50 59.1 106.000 48 3.8 94.000 44 21.9
129.000 52 59.0 117.000 50 46.3 105.000 47 47.0 93.000 44 1.4
128.000 52 49.7 116.000 50 33.2 104.000 47 30.0 92.000 43 40.6
127.000 52 40.0 115.000 50 19.7 103.000 47 12.6 91.000 43 19.5
126.000 52 30.1 114.000 50 5.9 102.000 46 54.9 90.000 42 58.2
125.000 52 19.8 113.000 49 51.8 101.000 46 36.9 89.000 42 36.5
124.000 52 9.3 112.000 49 37.3 100.000 46 18.5 88.000 42 14.6
123.000 51 58.4 111.000 49 22.5 99.000 45 59.8 87.000 41 52.4
122.000 51 47.2 110.000 49 7.4 98.000 45 40.9 86.000 41 30.0
121.000 51 35.6 109.000 48 52.0 97.000 45 21.6 85.000 41 7.3
120.000 51 23.8 108.000 48 36.3 96.000 45 2.0 84.000 40 44.3
119.000 51 11.6 107.000 48 20.2 95.000 44 42.1 83.000 40 21.1
MIN. GEOCENTRIC Prediction Comparison
U. T. SEP. Shift from nominal Prediction
h m " Path widths min.
6 9.1 1.81N 0.0 0.0 Goffin nominal, p. 86 of Feb. S&T
6 9.8 2.10N 4.9 N 0.7 late Gordon Garradd, 1998 March 17
6 9.7 2.09N 4.7 N 0.6 late Average, USNO & TMO, 1997 Nov-1998Mar05
6 9.5 2.04N 3.9 N 0.4 late USNO & TMO, extrapolated trends
David Dunham, IOTA, 1998 March 18, 7:30 UT (less than 23h to the event)