| 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 |
-0.502 |
| 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) |
| 2026-03-26 00:00 |
16:44:36.74 |
-20:57:59.8 |
HIP 81887 |
21.28 |
| 2026-03-26 12:00 |
16:44:36.02 |
-20:57:58.3 |
HIP 81887 |
21.15 |
| 2026-03-27 00:00 |
16:44:35.28 |
-20:57:56.8 |
HIP 81887 |
21.02 |
| 2026-03-27 12:00 |
16:44:34.53 |
-20:57:55.2 |
HIP 81887 |
20.89 |
| 2026-03-28 00:00 |
16:44:33.76 |
-20:57:53.6 |
HIP 81887 |
20.75 |
| 2026-03-28 12:00 |
16:44:32.98 |
-20:57:52.0 |
HIP 81887 |
20.61 |
| 2026-03-29 00:00 |
16:44:32.17 |
-20:57:50.4 |
HIP 81887 |
20.48 |
| 2026-03-29 12:00 |
16:44:31.35 |
-20:57:48.7 |
HIP 81887 |
20.34 |
| 2026-03-30 00:00 |
16:44:30.52 |
-20:57:47.0 |
HIP 81887 |
20.19 |
| 2026-03-30 12:00 |
16:44:29.67 |
-20:57:45.3 |
HIP 81887 |
20.05 |
| 2026-03-31 00:00 |
16:44:28.80 |
-20:57:43.5 |
HIP 81887 |
19.91 |
| 2026-03-31 12:00 |
16:44:27.92 |
-20:57:41.8 |
HIP 81887 |
19.76 |
| 2026-04-01 00:00 |
16:44:27.02 |
-20:57:40.0 |
HIP 81887 |
19.61 |
| 2026-04-01 12:00 |
16:44:26.10 |
-20:57:38.1 |
HIP 81887 |
19.46 |
| 2026-04-02 00:00 |
16:44:25.17 |
-20:57:36.3 |
HIP 81887 |
19.31 |
| 2026-04-02 12:00 |
16:44:24.23 |
-20:57:34.4 |
HIP 81887 |
19.16 |
| 2026-04-03 00:00 |
16:44:23.26 |
-20:57:32.5 |
HIP 81887 |
19.00 |
| 2026-04-03 12:00 |
16:44:22.28 |
-20:57:30.5 |
HIP 81887 |
18.85 |
| 2026-04-04 00:00 |
16:44:21.29 |
-20:57:28.6 |
HIP 81887 |
18.70 |
| 2026-04-04 12:00 |
16:44:20.28 |
-20:57:26.6 |
HIP 81887 |
18.54 |
| 2026-04-05 00:00 |
16:44:19.26 |
-20:57:24.6 |
HIP 81887 |
18.38 |
| 2026-04-05 12:00 |
16:44:18.22 |
-20:57:22.6 |
HIP 81887 |
18.23 |
| 2026-04-06 00:00 |
16:44:17.16 |
-20:57:20.5 |
HIP 81887 |
18.07 |
| 2026-04-06 12:00 |
16:44:16.09 |
-20:57:18.4 |
HIP 81887 |
17.91 |
| 2026-04-07 00:00 |
16:44:15.00 |
-20:57:16.3 |
HIP 81887 |
17.76 |
| 2026-04-07 12:00 |
16:44:13.90 |
-20:57:14.2 |
HIP 81887 |
17.60 |
| 2026-04-08 00:00 |
16:44:12.79 |
-20:57:12.0 |
HIP 81887 |
17.45 |
| 2026-04-08 12:00 |
16:44:11.66 |
-20:57:09.8 |
HIP 81887 |
17.29 |
| 2026-04-09 00:00 |
16:44:10.51 |
-20:57:07.6 |
HIP 81887 |
17.14 |
| 2026-04-09 12:00 |
16:44:09.35 |
-20:57:05.4 |
HIP 81887 |
16.98 |
| 2026-04-10 00:00 |
16:44:08.18 |
-20:57:03.1 |
HIP 81887 |
16.83 |
| 2026-04-10 12:00 |
16:44:06.99 |
-20:57:00.8 |
HIP 81887 |
16.68 |
| 2026-04-11 00:00 |
16:44:05.78 |
-20:56:58.5 |
HIP 81887 |
16.53 |
| 2026-04-11 12:00 |
16:44:04.56 |
-20:56:56.2 |
HIP 81887 |
16.39 |
| 2026-04-12 00:00 |
16:44:03.33 |
-20:56:53.9 |
HIP 81887 |
16.24 |
| 2026-04-12 12:00 |
16:44:02.09 |
-20:56:51.5 |
HIP 81887 |
16.10 |
| 2026-04-13 00:00 |
16:44:00.82 |
-20:56:49.1 |
HIP 81887 |
15.96 |
| 2026-04-13 12:00 |
16:43:59.55 |
-20:56:46.7 |
HIP 81887 |
15.82 |
| 2026-04-14 00:00 |
16:43:58.26 |
-20:56:44.2 |
HIP 81887 |
15.69 |
| 2026-04-14 12:00 |
16:43:56.96 |
-20:56:41.8 |
HIP 81887 |
15.56 |
| 2026-04-15 00:00 |
16:43:55.64 |
-20:56:39.3 |
HIP 81887 |
15.44 |
| 2026-04-15 12:00 |
16:43:54.31 |
-20:56:36.8 |
HIP 81887 |
15.31 |
| 2026-04-16 00:00 |
16:43:52.97 |
-20:56:34.2 |
HIP 81887 |
15.20 |