| 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) |
| 2026-07-29 00:00 |
08:43:46.57 |
+62:30:00.9 |
HIP 42882 |
5.47 |
| 2026-07-29 12:00 |
08:43:54.14 |
+62:29:45.4 |
HIP 42882 |
4.65 |
| 2026-07-30 00:00 |
08:44:01.71 |
+62:29:30.3 |
HIP 42882 |
3.87 |
| 2026-07-30 12:00 |
08:44:09.28 |
+62:29:15.5 |
HIP 42882 |
3.17 |
| 2026-07-31 00:00 |
08:44:16.85 |
+62:29:01.0 |
HIP 42882 |
2.60 |
| 2026-07-31 12:00 |
08:44:24.42 |
+62:28:46.8 |
HIP 42882 |
2.27 |
| 2026-08-01 00:00 |
08:44:31.99 |
+62:28:33.0 |
HIP 42882 |
2.29 |
| 2026-08-01 12:00 |
08:44:39.56 |
+62:28:19.4 |
HIP 42882 |
2.63 |
| 2026-08-02 00:00 |
08:44:47.12 |
+62:28:06.2 |
HIP 42882 |
3.21 |
| 2026-08-02 12:00 |
08:44:54.68 |
+62:27:53.3 |
HIP 42882 |
3.91 |
| 2026-08-03 00:00 |
08:45:02.24 |
+62:27:40.8 |
HIP 42882 |
4.68 |
| 2026-08-03 12:00 |
08:45:09.80 |
+62:27:28.6 |
HIP 42882 |
5.50 |
| 2026-08-04 00:00 |
08:45:17.35 |
+62:27:16.7 |
HIP 42882 |
6.33 |
| 2026-08-04 12:00 |
08:45:24.89 |
+62:27:05.1 |
HIP 42882 |
7.18 |
| 2026-08-05 00:00 |
08:45:32.43 |
+62:26:53.9 |
HIP 42882 |
8.04 |
| 2026-08-05 12:00 |
08:45:39.97 |
+62:26:42.9 |
HIP 42882 |
8.90 |
| 2026-08-06 00:00 |
08:45:47.50 |
+62:26:32.4 |
HIP 42882 |
9.77 |
| 2026-08-06 12:00 |
08:45:55.03 |
+62:26:22.1 |
HIP 42882 |
10.65 |
| 2026-08-07 00:00 |
08:46:02.54 |
+62:26:12.2 |
HIP 42882 |
11.52 |
| 2026-08-07 12:00 |
08:46:10.06 |
+62:26:02.6 |
HIP 42882 |
12.39 |
| 2026-08-08 00:00 |
08:46:17.56 |
+62:25:53.4 |
HIP 42882 |
13.27 |
| 2026-08-08 12:00 |
08:46:25.05 |
+62:25:44.4 |
HIP 42882 |
14.14 |
| 2026-08-09 00:00 |
08:46:32.54 |
+62:25:35.9 |
HIP 42882 |
15.01 |
| 2026-08-09 12:00 |
08:46:40.02 |
+62:25:27.6 |
HIP 42882 |
15.89 |
| 2026-08-10 00:00 |
08:46:47.49 |
+62:25:19.7 |
HIP 42882 |
16.76 |
| 2026-08-10 12:00 |
08:46:54.94 |
+62:25:12.2 |
HIP 42882 |
17.63 |
| 2026-08-11 00:00 |
08:47:02.39 |
+62:25:04.9 |
HIP 42882 |
18.50 |
| 2026-08-11 12:00 |
08:47:09.83 |
+62:24:58.0 |
HIP 42882 |
19.37 |
| 2026-08-12 00:00 |
08:47:17.25 |
+62:24:51.5 |
HIP 42882 |
20.23 |
| 2026-08-12 12:00 |
08:47:24.66 |
+62:24:45.3 |
HIP 42882 |
21.10 |
| 2026-08-13 00:00 |
08:47:32.06 |
+62:24:39.4 |
HIP 42882 |
21.96 |
| 2026-08-13 12:00 |
08:47:39.45 |
+62:24:33.9 |
HIP 42882 |
22.82 |
| 2026-08-14 00:00 |
08:47:46.82 |
+62:24:28.7 |
HIP 42882 |
23.68 |
| 2026-08-14 12:00 |
08:47:54.18 |
+62:24:23.9 |
HIP 42882 |
24.53 |
| 2026-08-15 00:00 |
08:48:01.52 |
+62:24:19.4 |
HIP 42882 |
25.38 |
| 2026-08-15 12:00 |
08:48:08.85 |
+62:24:15.2 |
HIP 42882 |
26.24 |
| 2026-08-16 00:00 |
08:48:16.16 |
+62:24:11.4 |
HIP 42882 |
27.09 |
| 2026-08-16 12:00 |
08:48:23.46 |
+62:24:08.0 |
HIP 42882 |
27.93 |
| 2026-08-17 00:00 |
08:48:30.73 |
+62:24:04.8 |
HIP 42882 |
28.78 |
| 2026-08-17 12:00 |
08:48:38.00 |
+62:24:02.1 |
HIP 42882 |
29.62 |
| 2026-08-18 00:00 |
08:48:45.24 |
+62:23:59.6 |
HIP 42882 |
30.46 |
| 2026-08-18 12:00 |
08:48:52.46 |
+62:23:57.6 |
HIP 42882 |
31.29 |
| 2026-08-19 00:00 |
08:48:59.67 |
+62:23:55.8 |
HIP 42882 |
32.13 |