| 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) |
| 2026-05-12 00:00 |
08:29:15.94 |
+64:01:52.9 |
HIP 42044 |
32.48 |
| 2026-05-12 12:00 |
08:29:17.70 |
+64:01:05.2 |
HIP 42044 |
32.37 |
| 2026-05-13 00:00 |
08:29:19.54 |
+64:00:17.4 |
HIP 42044 |
32.27 |
| 2026-05-13 12:00 |
08:29:21.45 |
+63:59:29.7 |
HIP 42044 |
32.18 |
| 2026-05-14 00:00 |
08:29:23.43 |
+63:58:42.1 |
HIP 42044 |
32.10 |
| 2026-05-14 12:00 |
08:29:25.48 |
+63:57:54.5 |
HIP 42044 |
32.04 |
| 2026-05-15 00:00 |
08:29:27.60 |
+63:57:07.0 |
HIP 42044 |
31.99 |
| 2026-05-15 12:00 |
08:29:29.79 |
+63:56:19.5 |
HIP 42044 |
31.95 |
| 2026-05-16 00:00 |
08:29:32.04 |
+63:55:32.0 |
HIP 42044 |
31.93 |
| 2026-05-16 12:00 |
08:29:34.37 |
+63:54:44.7 |
HIP 42044 |
31.92 |
| 2026-05-17 00:00 |
08:29:36.76 |
+63:53:57.4 |
HIP 42044 |
31.92 |
| 2026-05-17 12:00 |
08:29:39.23 |
+63:53:10.1 |
HIP 42044 |
31.94 |
| 2026-05-18 00:00 |
08:29:41.76 |
+63:52:23.0 |
HIP 42044 |
31.97 |
| 2026-05-18 12:00 |
08:29:44.35 |
+63:51:35.9 |
HIP 42044 |
32.02 |
| 2026-05-19 00:00 |
08:29:47.02 |
+63:50:48.9 |
HIP 42044 |
32.08 |
| 2026-05-19 12:00 |
08:29:49.75 |
+63:50:02.0 |
HIP 42045 |
31.68 |
| 2026-05-20 00:00 |
08:29:52.55 |
+63:49:15.1 |
HIP 42045 |
31.10 |
| 2026-05-20 12:00 |
08:29:55.41 |
+63:48:28.3 |
HIP 42045 |
30.52 |
| 2026-05-21 00:00 |
08:29:58.33 |
+63:47:41.7 |
HIP 42045 |
29.95 |
| 2026-05-21 12:00 |
08:30:01.33 |
+63:46:55.1 |
HIP 42045 |
29.38 |
| 2026-05-22 00:00 |
08:30:04.38 |
+63:46:08.6 |
HIP 42045 |
28.82 |
| 2026-05-22 12:00 |
08:30:07.50 |
+63:45:22.2 |
HIP 42045 |
28.27 |
| 2026-05-23 00:00 |
08:30:10.68 |
+63:44:35.9 |
HIP 42045 |
27.73 |
| 2026-05-23 12:00 |
08:30:13.93 |
+63:43:49.7 |
HIP 42045 |
27.19 |
| 2026-05-24 00:00 |
08:30:17.23 |
+63:43:03.6 |
HIP 42045 |
26.67 |
| 2026-05-24 12:00 |
08:30:20.60 |
+63:42:17.6 |
HIP 42045 |
26.15 |
| 2026-05-25 00:00 |
08:30:24.03 |
+63:41:31.7 |
HIP 42045 |
25.65 |
| 2026-05-25 12:00 |
08:30:27.52 |
+63:40:46.0 |
HIP 42045 |
25.16 |
| 2026-05-26 00:00 |
08:30:31.08 |
+63:40:00.3 |
HIP 42045 |
24.68 |
| 2026-05-26 12:00 |
08:30:34.69 |
+63:39:14.8 |
HIP 42045 |
24.22 |
| 2026-05-27 00:00 |
08:30:38.36 |
+63:38:29.4 |
HIP 42045 |
23.77 |
| 2026-05-27 12:00 |
08:30:42.09 |
+63:37:44.1 |
HIP 42045 |
23.34 |
| 2026-05-28 00:00 |
08:30:45.88 |
+63:36:58.9 |
HIP 42045 |
22.92 |
| 2026-05-28 12:00 |
08:30:49.73 |
+63:36:13.8 |
HIP 42045 |
22.52 |
| 2026-05-29 00:00 |
08:30:53.63 |
+63:35:28.9 |
HIP 42045 |
22.15 |
| 2026-05-29 12:00 |
08:30:57.60 |
+63:34:44.1 |
HIP 42045 |
21.79 |
| 2026-05-30 00:00 |
08:31:01.62 |
+63:33:59.5 |
HIP 42045 |
21.45 |
| 2026-05-30 12:00 |
08:31:05.69 |
+63:33:14.9 |
HIP 42045 |
21.14 |
| 2026-05-31 00:00 |
08:31:09.83 |
+63:32:30.5 |
HIP 42045 |
20.86 |
| 2026-05-31 12:00 |
08:31:14.01 |
+63:31:46.3 |
HIP 42045 |
20.60 |
| 2026-06-01 00:00 |
08:31:18.26 |
+63:31:02.1 |
HIP 42045 |
20.36 |
| 2026-06-01 12:00 |
08:31:22.56 |
+63:30:18.2 |
HIP 42045 |
20.16 |
| 2026-06-02 00:00 |
08:31:26.91 |
+63:29:34.3 |
HIP 42045 |
19.98 |