| Parameter |
Value |
| Designation |
C/1989 A6 (Shoemaker) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1988-11-02T02:05:44.491200Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:38Z |
| Obs used |
28 |
| NEO |
- |
| M1 |
13.300 |
| K1 |
4.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1989-02-10.0000000 |
| e |
1.00000000 |
| q (au) |
2.207946 |
| a (au) |
- |
| i (deg) |
25.505596 |
| Ω (om, deg) |
74.314457 |
| ω (w, deg) |
18.838143 |
| M (ma, deg) |
- |
Magnitude
Scatter + Global Linear
$$
M_a = (11.985 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
11.985 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-0.500 |
| k |
1.000 |
| δ90 |
10.000 |
| Parameter |
Symbol |
Range |
Description |
| Absolute magnitude at 1 AU from Sun and Earth |
H0 |
-5 to 20 |
Intrinsic brightness of the comet |
| Photometric slope parameter |
n |
2 to 6 |
Rate of brightness change with heliocentric distance |
| Forward scattering asymmetry factor |
gf |
0.8 to 1 |
Degree of forward scattering |
| Backward scattering asymmetry factor |
gb |
-1 to -0.5 |
Degree of backward scattering |
| Partitioning coefficient |
k |
0.8 to 1 |
Ratio between forward/backward scattering contributions |
| Dust-to-gas brightness ratio |
δ90 |
1 to 10 |
Relative contribution of dust scattering to gas emission |
Reference: EPSC-DPS2025-160
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-20 00:00 |
16:37:24.80 |
-20:47:45.8 |
HIP 81287 |
18.26 |
| 2026-09-20 12:00 |
16:37:25.46 |
-20:47:48.1 |
HIP 81287 |
18.42 |
| 2026-09-21 00:00 |
16:37:26.13 |
-20:47:50.5 |
HIP 81287 |
18.58 |
| 2026-09-21 12:00 |
16:37:26.82 |
-20:47:52.9 |
HIP 81287 |
18.75 |
| 2026-09-22 00:00 |
16:37:27.52 |
-20:47:55.4 |
HIP 81287 |
18.92 |
| 2026-09-22 12:00 |
16:37:28.25 |
-20:47:57.9 |
HIP 81287 |
19.09 |
| 2026-09-23 00:00 |
16:37:28.99 |
-20:48:00.4 |
HIP 81287 |
19.27 |
| 2026-09-23 12:00 |
16:37:29.74 |
-20:48:02.9 |
HIP 81287 |
19.45 |
| 2026-09-24 00:00 |
16:37:30.51 |
-20:48:05.5 |
HIP 81287 |
19.63 |
| 2026-09-24 12:00 |
16:37:31.30 |
-20:48:08.0 |
HIP 81287 |
19.82 |
| 2026-09-25 00:00 |
16:37:32.10 |
-20:48:10.7 |
HIP 81287 |
20.02 |
| 2026-09-25 12:00 |
16:37:32.92 |
-20:48:13.3 |
HIP 81287 |
20.21 |
| 2026-09-26 00:00 |
16:37:33.76 |
-20:48:16.0 |
HIP 81287 |
20.41 |
| 2026-09-26 12:00 |
16:37:34.61 |
-20:48:18.7 |
HIP 81287 |
20.62 |
| 2026-09-27 00:00 |
16:37:35.47 |
-20:48:21.4 |
HIP 81287 |
20.82 |
| 2026-09-27 12:00 |
16:37:36.36 |
-20:48:24.2 |
HIP 81287 |
21.03 |
| 2026-09-28 00:00 |
16:37:37.26 |
-20:48:27.0 |
HIP 81287 |
21.25 |
| 2026-09-28 12:00 |
16:37:38.17 |
-20:48:29.8 |
HIP 81287 |
21.47 |
| 2026-09-29 00:00 |
16:37:39.10 |
-20:48:32.7 |
HIP 81287 |
21.69 |
| 2026-09-29 12:00 |
16:37:40.04 |
-20:48:35.6 |
HIP 81287 |
21.92 |
| 2026-09-30 00:00 |
16:37:41.00 |
-20:48:38.5 |
HIP 81287 |
22.15 |
| 2026-09-30 12:00 |
16:37:41.98 |
-20:48:41.4 |
HIP 81287 |
22.38 |
| 2026-10-01 00:00 |
16:37:42.97 |
-20:48:44.4 |
HIP 81287 |
22.62 |
| 2026-10-01 12:00 |
16:37:43.98 |
-20:48:47.3 |
HIP 81287 |
22.86 |
| 2026-10-02 00:00 |
16:37:45.00 |
-20:48:50.4 |
HIP 81287 |
23.10 |
| 2026-10-02 12:00 |
16:37:46.04 |
-20:48:53.4 |
HIP 81287 |
23.35 |
| 2026-10-03 00:00 |
16:37:47.09 |
-20:48:56.5 |
HIP 81287 |
23.60 |
| 2026-10-03 12:00 |
16:37:48.16 |
-20:48:59.6 |
HIP 81287 |
23.85 |
| 2026-10-04 00:00 |
16:37:49.24 |
-20:49:02.7 |
HIP 81287 |
24.11 |
| 2026-10-04 12:00 |
16:37:50.34 |
-20:49:05.8 |
HIP 81287 |
24.37 |
| 2026-10-05 00:00 |
16:37:51.45 |
-20:49:09.0 |
HIP 81287 |
24.64 |
| 2026-10-05 12:00 |
16:37:52.58 |
-20:49:12.2 |
HIP 81287 |
24.90 |
| 2026-10-06 00:00 |
16:37:53.72 |
-20:49:15.4 |
HIP 81287 |
25.18 |
| 2026-10-06 12:00 |
16:37:54.88 |
-20:49:18.7 |
HIP 81287 |
25.45 |
| 2026-10-07 00:00 |
16:37:56.05 |
-20:49:22.0 |
HIP 81287 |
25.73 |
| 2026-10-07 12:00 |
16:37:57.23 |
-20:49:25.3 |
HIP 81287 |
26.01 |
| 2026-10-08 00:00 |
16:37:58.43 |
-20:49:28.6 |
HIP 81287 |
26.30 |
| 2026-10-08 12:00 |
16:37:59.65 |
-20:49:32.0 |
HIP 81287 |
26.59 |
| 2026-10-09 00:00 |
16:38:00.88 |
-20:49:35.3 |
HIP 81287 |
26.88 |
| 2026-10-09 12:00 |
16:38:02.12 |
-20:49:38.7 |
HIP 81287 |
27.17 |
| 2026-10-10 00:00 |
16:38:03.38 |
-20:49:42.2 |
HIP 81287 |
27.47 |
| 2026-10-10 12:00 |
16:38:04.65 |
-20:49:45.6 |
HIP 81287 |
27.78 |
| 2026-10-11 00:00 |
16:38:05.94 |
-20:49:49.1 |
HIP 81287 |
28.08 |