| 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) |
| 2026-06-01 00:00 |
10:21:57.88 |
+29:34:01.5 |
HIP 50642 |
18.07 |
| 2026-06-01 12:00 |
10:21:57.17 |
+29:33:10.8 |
HIP 50642 |
17.95 |
| 2026-06-02 00:00 |
10:21:56.57 |
+29:32:19.7 |
HIP 50642 |
17.89 |
| 2026-06-02 12:00 |
10:21:56.08 |
+29:31:28.3 |
HIP 50642 |
17.90 |
| 2026-06-03 00:00 |
10:21:55.69 |
+29:30:36.4 |
HIP 50642 |
17.98 |
| 2026-06-03 12:00 |
10:21:55.41 |
+29:29:44.3 |
HIP 50642 |
18.12 |
| 2026-06-04 00:00 |
10:21:55.24 |
+29:28:51.8 |
HIP 50642 |
18.33 |
| 2026-06-04 12:00 |
10:21:55.17 |
+29:27:59.0 |
HIP 50642 |
18.59 |
| 2026-06-05 00:00 |
10:21:55.21 |
+29:27:05.8 |
HIP 50642 |
18.92 |
| 2026-06-05 12:00 |
10:21:55.35 |
+29:26:12.3 |
HIP 50642 |
19.31 |
| 2026-06-06 00:00 |
10:21:55.60 |
+29:25:18.5 |
HIP 50642 |
19.75 |
| 2026-06-06 12:00 |
10:21:55.95 |
+29:24:24.3 |
HIP 50642 |
20.25 |
| 2026-06-07 00:00 |
10:21:56.41 |
+29:23:29.8 |
HIP 50642 |
20.79 |
| 2026-06-07 12:00 |
10:21:56.97 |
+29:22:35.1 |
HIP 50642 |
21.38 |
| 2026-06-08 00:00 |
10:21:57.63 |
+29:21:40.0 |
HIP 50642 |
22.02 |
| 2026-06-08 12:00 |
10:21:58.40 |
+29:20:44.6 |
HIP 50642 |
22.70 |
| 2026-06-09 00:00 |
10:21:59.27 |
+29:19:48.9 |
HIP 50642 |
23.41 |
| 2026-06-09 12:00 |
10:22:00.24 |
+29:18:53.0 |
HIP 50642 |
24.16 |
| 2026-06-10 00:00 |
10:22:01.31 |
+29:17:56.7 |
HIP 50642 |
24.95 |
| 2026-06-10 12:00 |
10:22:02.48 |
+29:17:00.2 |
HIP 50642 |
25.77 |
| 2026-06-11 00:00 |
10:22:03.76 |
+29:16:03.3 |
HIP 50642 |
26.61 |
| 2026-06-11 12:00 |
10:22:05.13 |
+29:15:06.3 |
HIP 50650 |
26.42 |
| 2026-06-12 00:00 |
10:22:06.60 |
+29:14:08.9 |
HIP 50650 |
26.00 |
| 2026-06-12 12:00 |
10:22:08.17 |
+29:13:11.3 |
HIP 50650 |
25.62 |
| 2026-06-13 00:00 |
10:22:09.84 |
+29:12:13.4 |
HIP 50650 |
25.29 |
| 2026-06-13 12:00 |
10:22:11.61 |
+29:11:15.3 |
HIP 50650 |
25.02 |
| 2026-06-14 00:00 |
10:22:13.47 |
+29:10:16.9 |
HIP 50650 |
24.80 |
| 2026-06-14 12:00 |
10:22:15.43 |
+29:09:18.3 |
HIP 50650 |
24.64 |
| 2026-06-15 00:00 |
10:22:17.49 |
+29:08:19.5 |
HIP 50650 |
24.54 |
| 2026-06-15 12:00 |
10:22:19.65 |
+29:07:20.4 |
HIP 50650 |
24.51 |
| 2026-06-16 00:00 |
10:22:21.89 |
+29:06:21.1 |
HIP 50650 |
24.54 |
| 2026-06-16 12:00 |
10:22:24.24 |
+29:05:21.6 |
HIP 50650 |
24.64 |
| 2026-06-17 00:00 |
10:22:26.68 |
+29:04:21.9 |
HIP 50650 |
24.81 |
| 2026-06-17 12:00 |
10:22:29.21 |
+29:03:21.9 |
HIP 50650 |
25.05 |
| 2026-06-18 00:00 |
10:22:31.83 |
+29:02:21.8 |
HIP 50650 |
25.36 |
| 2026-06-18 12:00 |
10:22:34.54 |
+29:01:21.5 |
HIP 50650 |
25.73 |
| 2026-06-19 00:00 |
10:22:37.35 |
+29:00:20.9 |
HIP 50650 |
26.17 |
| 2026-06-19 12:00 |
10:22:40.25 |
+28:59:20.2 |
HIP 50650 |
26.67 |
| 2026-06-20 00:00 |
10:22:43.24 |
+28:58:19.3 |
HIP 50650 |
27.24 |
| 2026-06-20 12:00 |
10:22:46.31 |
+28:57:18.3 |
HIP 50650 |
27.87 |
| 2026-06-21 00:00 |
10:22:49.48 |
+28:56:17.0 |
HIP 50650 |
28.56 |
| 2026-06-21 12:00 |
10:22:52.73 |
+28:55:15.6 |
HIP 50650 |
29.30 |
| 2026-06-22 00:00 |
10:22:56.08 |
+28:54:14.1 |
HIP 50730 |
29.10 |