| 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) |
| 2026-03-26 00:00 |
08:32:20.99 |
+65:12:22.8 |
HIP 42080 |
14.66 |
| 2026-03-26 12:00 |
08:32:15.20 |
+65:11:45.4 |
HIP 42080 |
15.11 |
| 2026-03-27 00:00 |
08:32:09.50 |
+65:11:07.8 |
HIP 42080 |
15.59 |
| 2026-03-27 12:00 |
08:32:03.88 |
+65:10:29.8 |
HIP 42080 |
16.09 |
| 2026-03-28 00:00 |
08:31:58.34 |
+65:09:51.6 |
HIP 42080 |
16.62 |
| 2026-03-28 12:00 |
08:31:52.87 |
+65:09:13.2 |
HIP 42080 |
17.17 |
| 2026-03-29 00:00 |
08:31:47.50 |
+65:08:34.5 |
HIP 42080 |
17.73 |
| 2026-03-29 12:00 |
08:31:42.20 |
+65:07:55.5 |
HIP 42080 |
18.30 |
| 2026-03-30 00:00 |
08:31:36.98 |
+65:07:16.3 |
HIP 42080 |
18.89 |
| 2026-03-30 12:00 |
08:31:31.85 |
+65:06:36.9 |
HIP 42080 |
19.50 |
| 2026-03-31 00:00 |
08:31:26.80 |
+65:05:57.2 |
HIP 42080 |
20.11 |
| 2026-03-31 12:00 |
08:31:21.83 |
+65:05:17.3 |
HIP 41838 |
19.93 |
| 2026-04-01 00:00 |
08:31:16.94 |
+65:04:37.1 |
HIP 41838 |
19.34 |
| 2026-04-01 12:00 |
08:31:12.13 |
+65:03:56.7 |
HIP 41838 |
18.77 |
| 2026-04-02 00:00 |
08:31:07.41 |
+65:03:16.1 |
HIP 41838 |
18.21 |
| 2026-04-02 12:00 |
08:31:02.77 |
+65:02:35.3 |
HIP 41838 |
17.66 |
| 2026-04-03 00:00 |
08:30:58.21 |
+65:01:54.2 |
HIP 41838 |
17.14 |
| 2026-04-03 12:00 |
08:30:53.74 |
+65:01:13.0 |
HIP 41838 |
16.63 |
| 2026-04-04 00:00 |
08:30:49.34 |
+65:00:31.5 |
HIP 41838 |
16.15 |
| 2026-04-04 12:00 |
08:30:45.04 |
+64:59:49.8 |
HIP 41838 |
15.68 |
| 2026-04-05 00:00 |
08:30:40.81 |
+64:59:07.8 |
HIP 41838 |
15.25 |
| 2026-04-05 12:00 |
08:30:36.67 |
+64:58:25.7 |
HIP 41838 |
14.83 |
| 2026-04-06 00:00 |
08:30:32.61 |
+64:57:43.4 |
HIP 41838 |
14.45 |
| 2026-04-06 12:00 |
08:30:28.63 |
+64:57:00.9 |
HIP 41838 |
14.10 |
| 2026-04-07 00:00 |
08:30:24.74 |
+64:56:18.2 |
HIP 41838 |
13.78 |
| 2026-04-07 12:00 |
08:30:20.93 |
+64:55:35.3 |
HIP 41838 |
13.49 |
| 2026-04-08 00:00 |
08:30:17.20 |
+64:54:52.2 |
HIP 41838 |
13.25 |
| 2026-04-08 12:00 |
08:30:13.56 |
+64:54:08.9 |
HIP 41838 |
13.03 |
| 2026-04-09 00:00 |
08:30:10.00 |
+64:53:25.5 |
HIP 41838 |
12.86 |
| 2026-04-09 12:00 |
08:30:06.52 |
+64:52:41.9 |
HIP 41838 |
12.74 |
| 2026-04-10 00:00 |
08:30:03.13 |
+64:51:58.1 |
HIP 41838 |
12.65 |
| 2026-04-10 12:00 |
08:29:59.82 |
+64:51:14.1 |
HIP 41838 |
12.61 |
| 2026-04-11 00:00 |
08:29:56.60 |
+64:50:30.0 |
HIP 41838 |
12.61 |
| 2026-04-11 12:00 |
08:29:53.46 |
+64:49:45.7 |
HIP 41838 |
12.65 |
| 2026-04-12 00:00 |
08:29:50.40 |
+64:49:01.2 |
HIP 41838 |
12.74 |
| 2026-04-12 12:00 |
08:29:47.43 |
+64:48:16.6 |
HIP 41838 |
12.86 |
| 2026-04-13 00:00 |
08:29:44.54 |
+64:47:31.8 |
HIP 41838 |
13.03 |
| 2026-04-13 12:00 |
08:29:41.74 |
+64:46:46.9 |
HIP 41838 |
13.24 |
| 2026-04-14 00:00 |
08:29:39.02 |
+64:46:01.8 |
HIP 41838 |
13.48 |
| 2026-04-14 12:00 |
08:29:36.38 |
+64:45:16.6 |
HIP 41838 |
13.76 |
| 2026-04-15 00:00 |
08:29:33.83 |
+64:44:31.3 |
HIP 41838 |
14.06 |
| 2026-04-15 12:00 |
08:29:31.36 |
+64:43:45.8 |
HIP 41838 |
14.40 |
| 2026-04-16 00:00 |
08:29:28.98 |
+64:43:00.2 |
HIP 41838 |
14.77 |