| Parameter |
Value |
| Designation |
389P/Siding Spring |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2020-01-02T20:23:08.842560Z |
| Orbit solution date (soln_date, UTC) |
2022-07-31T01:43:35Z |
| Obs used |
103 |
| NEO |
- |
| M1 |
14.300 |
| K1 |
19.500 |
| PC |
0.030 |
| Discovery observation (MPC, UTC) |
2019-09-25T12:36:33.696000Z |
| Discovery magnitude (MPC) |
20.50 w |
| Discovery observatory (MPC) |
F51 · Pan-STARRS 1, Haleakala |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2013-11-08.0000000 |
| e |
0.70466929 |
| q (au) |
1.659623 |
| a (au) |
5.619542 |
| i (deg) |
160.071918 |
| Ω (om, deg) |
218.811242 |
| ω (w, deg) |
249.490302 |
| M (ma, deg) |
193.763391 |
Magnitude
Scatter + Global Linear
$$
M_a = (14.922 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
14.922 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.937 |
| k |
0.999 |
| 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) |
| 2026-07-29 00:00 |
10:30:24.27 |
+27:35:46.7 |
HIP 51406 |
14.89 |
| 2026-07-29 12:00 |
10:30:32.46 |
+27:34:44.9 |
HIP 51440 |
14.80 |
| 2026-07-30 00:00 |
10:30:40.69 |
+27:33:43.3 |
HIP 51440 |
14.22 |
| 2026-07-30 12:00 |
10:30:48.97 |
+27:32:41.8 |
HIP 51440 |
13.94 |
| 2026-07-31 00:00 |
10:30:57.28 |
+27:31:40.4 |
HIP 51440 |
13.99 |
| 2026-07-31 12:00 |
10:31:05.63 |
+27:30:39.2 |
HIP 51440 |
14.35 |
| 2026-08-01 00:00 |
10:31:14.02 |
+27:29:38.2 |
HIP 51440 |
15.02 |
| 2026-08-01 12:00 |
10:31:22.45 |
+27:28:37.3 |
HIP 51440 |
15.95 |
| 2026-08-02 00:00 |
10:31:30.92 |
+27:27:36.5 |
HIP 51440 |
17.11 |
| 2026-08-02 12:00 |
10:31:39.43 |
+27:26:36.0 |
HIP 51440 |
18.45 |
| 2026-08-03 00:00 |
10:31:47.97 |
+27:25:35.6 |
HIP 51440 |
19.94 |
| 2026-08-03 12:00 |
10:31:56.55 |
+27:24:35.4 |
HIP 51440 |
21.55 |
| 2026-08-04 00:00 |
10:32:05.16 |
+27:23:35.4 |
HIP 51440 |
23.26 |
| 2026-08-04 12:00 |
10:32:13.81 |
+27:22:35.5 |
HIP 51440 |
25.05 |
| 2026-08-05 00:00 |
10:32:22.49 |
+27:21:35.9 |
HIP 51440 |
26.90 |
| 2026-08-05 12:00 |
10:32:31.21 |
+27:20:36.4 |
HIP 51664 |
27.83 |
| 2026-08-06 00:00 |
10:32:39.96 |
+27:19:37.1 |
HIP 51664 |
28.12 |
| 2026-08-06 12:00 |
10:32:48.74 |
+27:18:38.0 |
HIP 51664 |
28.58 |
| 2026-08-07 00:00 |
10:32:57.56 |
+27:17:39.1 |
HIP 51664 |
29.19 |
| 2026-08-07 12:00 |
10:33:06.40 |
+27:16:40.4 |
HIP 51823 |
28.64 |
| 2026-08-08 00:00 |
10:33:15.28 |
+27:15:42.0 |
HIP 51823 |
26.60 |
| 2026-08-08 12:00 |
10:33:24.19 |
+27:14:43.7 |
HIP 51823 |
24.58 |
| 2026-08-09 00:00 |
10:33:33.13 |
+27:13:45.6 |
HIP 51823 |
22.59 |
| 2026-08-09 12:00 |
10:33:42.10 |
+27:12:47.8 |
HIP 51823 |
20.63 |
| 2026-08-10 00:00 |
10:33:51.09 |
+27:11:50.2 |
HIP 51823 |
18.73 |
| 2026-08-10 12:00 |
10:34:00.12 |
+27:10:52.8 |
HIP 51823 |
16.90 |
| 2026-08-11 00:00 |
10:34:09.17 |
+27:09:55.7 |
HIP 51823 |
15.16 |
| 2026-08-11 12:00 |
10:34:18.25 |
+27:08:58.8 |
HIP 51823 |
13.56 |
| 2026-08-12 00:00 |
10:34:27.35 |
+27:08:02.1 |
HIP 51823 |
12.15 |
| 2026-08-12 12:00 |
10:34:36.48 |
+27:07:05.7 |
HIP 51823 |
11.02 |
| 2026-08-13 00:00 |
10:34:45.63 |
+27:06:09.5 |
HIP 51823 |
10.24 |
| 2026-08-13 12:00 |
10:34:54.81 |
+27:05:13.6 |
HIP 51823 |
9.91 |
| 2026-08-14 00:00 |
10:35:04.01 |
+27:04:17.9 |
HIP 51823 |
10.08 |
| 2026-08-14 12:00 |
10:35:13.23 |
+27:03:22.5 |
HIP 51823 |
10.72 |
| 2026-08-15 00:00 |
10:35:22.48 |
+27:02:27.4 |
HIP 51823 |
11.76 |
| 2026-08-15 12:00 |
10:35:31.74 |
+27:01:32.5 |
HIP 51823 |
13.11 |
| 2026-08-16 00:00 |
10:35:41.03 |
+27:00:37.9 |
HIP 51823 |
14.68 |
| 2026-08-16 12:00 |
10:35:50.34 |
+26:59:43.6 |
HIP 51823 |
16.41 |
| 2026-08-17 00:00 |
10:35:59.66 |
+26:58:49.6 |
HIP 51823 |
18.25 |
| 2026-08-17 12:00 |
10:36:09.00 |
+26:57:55.8 |
HIP 51893 |
19.26 |
| 2026-08-18 00:00 |
10:36:18.37 |
+26:57:02.3 |
HIP 51893 |
20.29 |
| 2026-08-18 12:00 |
10:36:27.75 |
+26:56:09.2 |
HIP 51893 |
21.50 |
| 2026-08-19 00:00 |
10:36:37.14 |
+26:55:16.3 |
HIP 51893 |
22.87 |