| 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) |
| 2026-06-01 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 |
| 2026-06-02 12:00 |
20:56:08.36 |
+44:51:25.7 |
HIP 103371 |
6.19 |
| 2026-06-03 00:00 |
20:56:05.63 |
+44:52:06.7 |
HIP 103371 |
6.16 |
| 2026-06-03 12:00 |
20:56:02.87 |
+44:52:47.5 |
HIP 103371 |
6.26 |
| 2026-06-04 00:00 |
20:56:00.08 |
+44:53:28.0 |
HIP 103371 |
6.47 |
| 2026-06-04 12:00 |
20:55:57.24 |
+44:54:08.3 |
HIP 103371 |
6.78 |
| 2026-06-05 00:00 |
20:55:54.37 |
+44:54:48.3 |
HIP 103371 |
7.18 |
| 2026-06-05 12:00 |
20:55:51.47 |
+44:55:28.0 |
HIP 103371 |
7.67 |
| 2026-06-06 00:00 |
20:55:48.52 |
+44:56:07.5 |
HIP 103371 |
8.21 |
| 2026-06-06 12:00 |
20:55:45.54 |
+44:56:46.7 |
HIP 103371 |
8.81 |
| 2026-06-07 00:00 |
20:55:42.52 |
+44:57:25.6 |
HIP 103371 |
9.45 |
| 2026-06-07 12:00 |
20:55:39.47 |
+44:58:04.2 |
HIP 103371 |
10.12 |
| 2026-06-08 00:00 |
20:55:36.38 |
+44:58:42.6 |
HIP 103371 |
10.82 |
| 2026-06-08 12:00 |
20:55:33.26 |
+44:59:20.7 |
HIP 103371 |
11.55 |
| 2026-06-09 00:00 |
20:55:30.10 |
+44:59:58.5 |
HIP 103222 |
11.40 |
| 2026-06-09 12:00 |
20:55:26.90 |
+45:00:36.0 |
HIP 103222 |
10.55 |
| 2026-06-10 00:00 |
20:55:23.67 |
+45:01:13.2 |
HIP 103222 |
9.71 |
| 2026-06-10 12:00 |
20:55:20.41 |
+45:01:50.1 |
HIP 103222 |
8.87 |
| 2026-06-11 00:00 |
20:55:17.11 |
+45:02:26.7 |
HIP 103222 |
8.02 |
| 2026-06-11 12:00 |
20:55:13.77 |
+45:03:03.0 |
HIP 103222 |
7.18 |
| 2026-06-12 00:00 |
20:55:10.40 |
+45:03:39.1 |
HIP 103222 |
6.33 |
| 2026-06-12 12:00 |
20:55:07.00 |
+45:04:14.8 |
HIP 103222 |
5.49 |
| 2026-06-13 00:00 |
20:55:03.56 |
+45:04:50.2 |
HIP 103222 |
4.64 |
| 2026-06-13 12:00 |
20:55:00.09 |
+45:05:25.3 |
HIP 103222 |
3.80 |
| 2026-06-14 00:00 |
20:54:56.58 |
+45:06:00.1 |
HIP 103222 |
2.95 |
| 2026-06-14 12:00 |
20:54:53.04 |
+45:06:34.5 |
HIP 103222 |
2.11 |
| 2026-06-15 00:00 |
20:54:49.47 |
+45:07:08.7 |
HIP 103222 |
1.27 |
| 2026-06-15 12:00 |
20:54:45.86 |
+45:07:42.5 |
HIP 103222 |
0.48 |
| 2026-06-16 00:00 |
20:54:42.23 |
+45:08:16.0 |
HIP 103222 |
0.55 |
| 2026-06-16 12:00 |
20:54:38.56 |
+45:08:49.1 |
HIP 103222 |
1.35 |
| 2026-06-17 00:00 |
20:54:34.85 |
+45:09:22.0 |
HIP 103222 |
2.19 |
| 2026-06-17 12:00 |
20:54:31.12 |
+45:09:54.5 |
HIP 103222 |
3.04 |
| 2026-06-18 00:00 |
20:54:27.36 |
+45:10:26.6 |
HIP 103222 |
3.89 |
| 2026-06-18 12:00 |
20:54:23.56 |
+45:10:58.5 |
HIP 103222 |
4.74 |
| 2026-06-19 00:00 |
20:54:19.73 |
+45:11:30.0 |
HIP 103167 |
5.46 |
| 2026-06-19 12:00 |
20:54:15.87 |
+45:12:01.1 |
HIP 103167 |
5.69 |
| 2026-06-20 00:00 |
20:54:11.99 |
+45:12:31.9 |
HIP 103167 |
6.02 |
| 2026-06-20 12:00 |
20:54:08.07 |
+45:13:02.4 |
HIP 103167 |
6.44 |
| 2026-06-21 00:00 |
20:54:04.12 |
+45:13:32.5 |
HIP 103167 |
6.94 |
| 2026-06-21 12:00 |
20:54:00.14 |
+45:14:02.2 |
HIP 103167 |
7.50 |
| 2026-06-22 00:00 |
20:53:56.14 |
+45:14:31.7 |
HIP 103094 |
7.55 |