| Parameter |
Value |
| Designation |
C/2012 OP (Siding Spring) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2012-12-04T17:50:22.822080Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:32:19Z |
| Obs used |
100 |
| NEO |
- |
| M1 |
14.400 |
| K1 |
4.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2013-01-23.0000000 |
| e |
0.99657940 |
| q (au) |
3.607071 |
| a (au) |
1054.514944 |
| i (deg) |
114.828786 |
| Ω (om, deg) |
267.370339 |
| ω (w, deg) |
351.435364 |
| M (ma, deg) |
0.001418 |
Magnitude
Scatter + Global Linear
$$
M_a = (H_0 + n\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
- |
| n |
- |
| gf |
- |
| gb |
- |
| k |
- |
| δ90 |
- |
| 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 |
08:55:41.63 |
+62:33:57.4 |
HIP 43696 |
11.81 |
| 2026-09-20 12:00 |
08:55:46.66 |
+62:34:17.7 |
HIP 43696 |
12.36 |
| 2026-09-21 00:00 |
08:55:51.64 |
+62:34:38.3 |
HIP 43696 |
12.92 |
| 2026-09-21 12:00 |
08:55:56.57 |
+62:34:59.3 |
HIP 43999 |
12.70 |
| 2026-09-22 00:00 |
08:56:01.45 |
+62:35:20.6 |
HIP 43999 |
12.03 |
| 2026-09-22 12:00 |
08:56:06.28 |
+62:35:42.2 |
HIP 43999 |
11.37 |
| 2026-09-23 00:00 |
08:56:11.06 |
+62:36:04.1 |
HIP 43999 |
10.72 |
| 2026-09-23 12:00 |
08:56:15.79 |
+62:36:26.3 |
HIP 43999 |
10.06 |
| 2026-09-24 00:00 |
08:56:20.47 |
+62:36:48.9 |
HIP 43999 |
9.41 |
| 2026-09-24 12:00 |
08:56:25.10 |
+62:37:11.7 |
HIP 43999 |
8.77 |
| 2026-09-25 00:00 |
08:56:29.68 |
+62:37:34.9 |
HIP 43999 |
8.13 |
| 2026-09-25 12:00 |
08:56:34.21 |
+62:37:58.3 |
HIP 43999 |
7.49 |
| 2026-09-26 00:00 |
08:56:38.68 |
+62:38:22.1 |
HIP 43999 |
6.86 |
| 2026-09-26 12:00 |
08:56:43.11 |
+62:38:46.2 |
HIP 43999 |
6.24 |
| 2026-09-27 00:00 |
08:56:47.47 |
+62:39:10.6 |
HIP 43999 |
5.63 |
| 2026-09-27 12:00 |
08:56:51.79 |
+62:39:35.2 |
HIP 43999 |
5.04 |
| 2026-09-28 00:00 |
08:56:56.05 |
+62:40:00.2 |
HIP 43999 |
4.46 |
| 2026-09-28 12:00 |
08:57:00.26 |
+62:40:25.5 |
HIP 43999 |
3.91 |
| 2026-09-29 00:00 |
08:57:04.41 |
+62:40:51.1 |
HIP 43999 |
3.39 |
| 2026-09-29 12:00 |
08:57:08.51 |
+62:41:17.0 |
HIP 43999 |
2.93 |
| 2026-09-30 00:00 |
08:57:12.55 |
+62:41:43.2 |
HIP 43999 |
2.56 |
| 2026-09-30 12:00 |
08:57:16.54 |
+62:42:09.7 |
HIP 43999 |
2.32 |
| 2026-10-01 00:00 |
08:57:20.47 |
+62:42:36.5 |
HIP 43999 |
2.24 |
| 2026-10-01 12:00 |
08:57:24.35 |
+62:43:03.5 |
HIP 43999 |
2.35 |
| 2026-10-02 00:00 |
08:57:28.17 |
+62:43:30.9 |
HIP 43999 |
2.62 |
| 2026-10-02 12:00 |
08:57:31.93 |
+62:43:58.5 |
HIP 43999 |
3.00 |
| 2026-10-03 00:00 |
08:57:35.63 |
+62:44:26.5 |
HIP 43999 |
3.46 |
| 2026-10-03 12:00 |
08:57:39.28 |
+62:44:54.7 |
HIP 43999 |
3.98 |
| 2026-10-04 00:00 |
08:57:42.86 |
+62:45:23.2 |
HIP 43999 |
4.52 |
| 2026-10-04 12:00 |
08:57:46.39 |
+62:45:52.0 |
HIP 43999 |
5.09 |
| 2026-10-05 00:00 |
08:57:49.86 |
+62:46:21.1 |
HIP 43999 |
5.67 |
| 2026-10-05 12:00 |
08:57:53.26 |
+62:46:50.5 |
HIP 43999 |
6.26 |
| 2026-10-06 00:00 |
08:57:56.61 |
+62:47:20.1 |
HIP 43999 |
6.86 |
| 2026-10-06 12:00 |
08:57:59.90 |
+62:47:50.1 |
HIP 43999 |
7.47 |
| 2026-10-07 00:00 |
08:58:03.12 |
+62:48:20.3 |
HIP 43999 |
8.08 |
| 2026-10-07 12:00 |
08:58:06.29 |
+62:48:50.7 |
HIP 43999 |
8.69 |
| 2026-10-08 00:00 |
08:58:09.39 |
+62:49:21.5 |
HIP 43999 |
9.31 |
| 2026-10-08 12:00 |
08:58:12.43 |
+62:49:52.5 |
HIP 43999 |
9.92 |
| 2026-10-09 00:00 |
08:58:15.41 |
+62:50:23.8 |
HIP 43999 |
10.54 |
| 2026-10-09 12:00 |
08:58:18.32 |
+62:50:55.3 |
HIP 43999 |
11.16 |
| 2026-10-10 00:00 |
08:58:21.17 |
+62:51:27.2 |
HIP 43999 |
11.78 |
| 2026-10-10 12:00 |
08:58:23.95 |
+62:51:59.2 |
HIP 43999 |
12.40 |
| 2026-10-11 00:00 |
08:58:26.68 |
+62:52:31.6 |
HIP 43999 |
13.02 |