| Parameter |
Value |
| Designation |
C/2010 A4 (Siding Spring) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2010-10-08T17:46:24.746880Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:31:39Z |
| Obs used |
140 |
| NEO |
- |
| M1 |
7.100 |
| K1 |
15.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2010-05-04.0000000 |
| e |
0.99062596 |
| q (au) |
2.737996 |
| a (au) |
292.082906 |
| i (deg) |
96.730138 |
| Ω (om, deg) |
346.685502 |
| ω (w, deg) |
271.685276 |
| M (ma, deg) |
359.968855 |
Magnitude
Scatter + Global Linear
$$
M_a = (7.590 + 5.685\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
7.590 |
| n |
5.685 |
| gf |
1.000 |
| gb |
-1.000 |
| k |
0.998 |
| 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) |
| 2026-05-12 00:00 |
20:57:28.28 |
+44:18:41.7 |
HIP 103519 |
13.24 |
| 2026-05-12 12:00 |
20:57:27.28 |
+44:19:30.9 |
HIP 103519 |
12.79 |
| 2026-05-13 00:00 |
20:57:26.24 |
+44:20:20.0 |
HIP 103519 |
12.39 |
| 2026-05-13 12:00 |
20:57:25.15 |
+44:21:08.9 |
HIP 103519 |
12.03 |
| 2026-05-14 00:00 |
20:57:24.03 |
+44:21:57.7 |
HIP 103519 |
11.74 |
| 2026-05-14 12:00 |
20:57:22.86 |
+44:22:46.4 |
HIP 103519 |
11.50 |
| 2026-05-15 00:00 |
20:57:21.65 |
+44:23:34.9 |
HIP 103519 |
11.33 |
| 2026-05-15 12:00 |
20:57:20.39 |
+44:24:23.3 |
HIP 103519 |
11.23 |
| 2026-05-16 00:00 |
20:57:19.10 |
+44:25:11.6 |
HIP 103519 |
11.20 |
| 2026-05-16 12:00 |
20:57:17.77 |
+44:25:59.7 |
HIP 103519 |
11.23 |
| 2026-05-17 00:00 |
20:57:16.39 |
+44:26:47.6 |
HIP 103519 |
11.34 |
| 2026-05-17 12:00 |
20:57:14.97 |
+44:27:35.4 |
HIP 103519 |
11.51 |
| 2026-05-18 00:00 |
20:57:13.51 |
+44:28:23.1 |
HIP 103519 |
11.75 |
| 2026-05-18 12:00 |
20:57:12.01 |
+44:29:10.6 |
HIP 103519 |
12.05 |
| 2026-05-19 00:00 |
20:57:10.47 |
+44:29:57.9 |
HIP 103519 |
12.40 |
| 2026-05-19 12:00 |
20:57:08.89 |
+44:30:45.1 |
HIP 103519 |
12.81 |
| 2026-05-20 00:00 |
20:57:07.26 |
+44:31:32.1 |
HIP 103519 |
13.26 |
| 2026-05-20 12:00 |
20:57:05.60 |
+44:32:18.9 |
HIP 103519 |
13.76 |
| 2026-05-21 00:00 |
20:57:03.89 |
+44:33:05.6 |
HIP 103519 |
14.29 |
| 2026-05-21 12:00 |
20:57:02.15 |
+44:33:52.0 |
HIP 103519 |
14.85 |
| 2026-05-22 00:00 |
20:57:00.36 |
+44:34:38.3 |
HIP 103519 |
15.45 |
| 2026-05-22 12:00 |
20:56:58.53 |
+44:35:24.4 |
HIP 103476 |
15.35 |
| 2026-05-23 00:00 |
20:56:56.66 |
+44:36:10.3 |
HIP 103476 |
14.98 |
| 2026-05-23 12:00 |
20:56:54.76 |
+44:36:56.1 |
HIP 103476 |
14.66 |
| 2026-05-24 00:00 |
20:56:52.81 |
+44:37:41.6 |
HIP 103476 |
14.39 |
| 2026-05-24 12:00 |
20:56:50.82 |
+44:38:26.9 |
HIP 103476 |
14.18 |
| 2026-05-25 00:00 |
20:56:48.79 |
+44:39:12.0 |
HIP 103476 |
14.01 |
| 2026-05-25 12:00 |
20:56:46.73 |
+44:39:57.0 |
HIP 103476 |
13.90 |
| 2026-05-26 00:00 |
20:56:44.62 |
+44:40:41.7 |
HIP 103476 |
13.85 |
| 2026-05-26 12:00 |
20:56:42.47 |
+44:41:26.2 |
HIP 103476 |
13.85 |
| 2026-05-27 00:00 |
20:56:40.29 |
+44:42:10.5 |
HIP 103371 |
13.34 |
| 2026-05-27 12:00 |
20:56:38.06 |
+44:42:54.6 |
HIP 103371 |
12.59 |
| 2026-05-28 00:00 |
20:56:35.80 |
+44:43:38.4 |
HIP 103371 |
11.84 |
| 2026-05-28 12:00 |
20:56:33.50 |
+44:44:22.1 |
HIP 103371 |
11.12 |
| 2026-05-29 00:00 |
20:56:31.16 |
+44:45:05.5 |
HIP 103371 |
10.41 |
| 2026-05-29 12:00 |
20:56:28.78 |
+44:45:48.7 |
HIP 103371 |
9.73 |
| 2026-05-30 00:00 |
20:56:26.36 |
+44:46:31.6 |
HIP 103371 |
9.08 |
| 2026-05-30 12:00 |
20:56:23.90 |
+44:47:14.4 |
HIP 103371 |
8.47 |
| 2026-05-31 00:00 |
20:56:21.40 |
+44:47:56.9 |
HIP 103371 |
7.90 |
| 2026-05-31 12:00 |
20:56:18.87 |
+44:48:39.1 |
HIP 103371 |
7.39 |
| 2026-06-01 00:00 |
20:56:16.30 |
+44:49:21.1 |
HIP 103371 |
6.95 |
| 2026-06-01 12:00 |
20:56:13.69 |
+44:50:02.9 |
HIP 103371 |
6.60 |
| 2026-06-02 00:00 |
20:56:11.04 |
+44:50:44.4 |
HIP 103371 |
6.34 |