| 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) |
| 2026-07-29 00:00 |
20:48:00.55 |
+45:32:39.4 |
HIP 102687 |
7.14 |
| 2026-07-29 12:00 |
20:47:55.28 |
+45:32:38.4 |
HIP 102585 |
6.42 |
| 2026-07-30 00:00 |
20:47:50.01 |
+45:32:36.9 |
HIP 102585 |
5.57 |
| 2026-07-30 12:00 |
20:47:44.74 |
+45:32:35.0 |
HIP 102585 |
4.75 |
| 2026-07-31 00:00 |
20:47:39.47 |
+45:32:32.7 |
HIP 102585 |
3.97 |
| 2026-07-31 12:00 |
20:47:34.19 |
+45:32:29.9 |
HIP 102585 |
3.29 |
| 2026-08-01 00:00 |
20:47:28.92 |
+45:32:26.7 |
HIP 102585 |
2.75 |
| 2026-08-01 12:00 |
20:47:23.64 |
+45:32:23.1 |
HIP 102585 |
2.47 |
| 2026-08-02 00:00 |
20:47:18.36 |
+45:32:19.1 |
HIP 102585 |
2.52 |
| 2026-08-02 12:00 |
20:47:13.09 |
+45:32:14.6 |
HIP 102585 |
2.89 |
| 2026-08-03 00:00 |
20:47:07.81 |
+45:32:09.7 |
HIP 102585 |
3.48 |
| 2026-08-03 12:00 |
20:47:02.54 |
+45:32:04.4 |
HIP 102585 |
4.20 |
| 2026-08-04 00:00 |
20:46:57.26 |
+45:31:58.6 |
HIP 102585 |
4.99 |
| 2026-08-04 12:00 |
20:46:51.99 |
+45:31:52.4 |
HIP 102585 |
5.83 |
| 2026-08-05 00:00 |
20:46:46.72 |
+45:31:45.8 |
HIP 102585 |
6.69 |
| 2026-08-05 12:00 |
20:46:41.45 |
+45:31:38.8 |
HIP 102585 |
7.57 |
| 2026-08-06 00:00 |
20:46:36.19 |
+45:31:31.3 |
HIP 102585 |
8.46 |
| 2026-08-06 12:00 |
20:46:30.92 |
+45:31:23.4 |
HIP 102585 |
9.37 |
| 2026-08-07 00:00 |
20:46:25.67 |
+45:31:15.1 |
HIP 102585 |
10.28 |
| 2026-08-07 12:00 |
20:46:20.41 |
+45:31:06.4 |
HIP 102585 |
11.19 |
| 2026-08-08 00:00 |
20:46:15.16 |
+45:30:57.2 |
HIP 102585 |
12.11 |
| 2026-08-08 12:00 |
20:46:09.92 |
+45:30:47.6 |
HIP 102585 |
13.04 |
| 2026-08-09 00:00 |
20:46:04.68 |
+45:30:37.6 |
HIP 102585 |
13.96 |
| 2026-08-09 12:00 |
20:45:59.44 |
+45:30:27.2 |
HIP 102585 |
14.89 |
| 2026-08-10 00:00 |
20:45:54.21 |
+45:30:16.3 |
HIP 102585 |
15.82 |
| 2026-08-10 12:00 |
20:45:48.99 |
+45:30:05.0 |
HIP 102585 |
16.75 |
| 2026-08-11 00:00 |
20:45:43.78 |
+45:29:53.3 |
HIP 102585 |
17.68 |
| 2026-08-11 12:00 |
20:45:38.57 |
+45:29:41.2 |
HIP 102585 |
18.61 |
| 2026-08-12 00:00 |
20:45:33.37 |
+45:29:28.7 |
HIP 102585 |
19.54 |
| 2026-08-12 12:00 |
20:45:28.18 |
+45:29:15.7 |
HIP 102585 |
20.48 |
| 2026-08-13 00:00 |
20:45:23.00 |
+45:29:02.4 |
HIP 102585 |
21.41 |
| 2026-08-13 12:00 |
20:45:17.83 |
+45:28:48.6 |
HIP 102585 |
22.35 |
| 2026-08-14 00:00 |
20:45:12.66 |
+45:28:34.4 |
HIP 102585 |
23.28 |
| 2026-08-14 12:00 |
20:45:07.51 |
+45:28:19.8 |
HIP 102585 |
24.22 |
| 2026-08-15 00:00 |
20:45:02.37 |
+45:28:04.8 |
HIP 102585 |
25.16 |
| 2026-08-15 12:00 |
20:44:57.23 |
+45:27:49.3 |
HIP 102585 |
26.09 |
| 2026-08-16 00:00 |
20:44:52.11 |
+45:27:33.5 |
HIP 102585 |
27.03 |
| 2026-08-16 12:00 |
20:44:47.00 |
+45:27:17.3 |
HIP 102585 |
27.96 |
| 2026-08-17 00:00 |
20:44:41.91 |
+45:27:00.6 |
HIP 102585 |
28.90 |
| 2026-08-17 12:00 |
20:44:36.82 |
+45:26:43.6 |
HIP 102585 |
29.83 |
| 2026-08-18 00:00 |
20:44:31.75 |
+45:26:26.2 |
HIP 102585 |
30.77 |
| 2026-08-18 12:00 |
20:44:26.69 |
+45:26:08.3 |
HIP 102585 |
31.70 |
| 2026-08-19 00:00 |
20:44:21.65 |
+45:25:50.1 |
HIP 102189 |
31.73 |