| Parameter |
Value |
| Designation |
C/2004 T3 (Siding Spring) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2003-04-15T07:36:04.478400Z |
| Orbit solution date (soln_date, UTC) |
2026-06-09T11:12:22Z |
| Obs used |
110 |
| NEO |
- |
| M1 |
6.400 |
| K1 |
7.250 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2005-02-10.0000000 |
| e |
0.99847370 |
| q (au) |
8.864377 |
| a (au) |
5807.750491 |
| i (deg) |
71.964273 |
| Ω (om, deg) |
50.354719 |
| ω (w, deg) |
259.687076 |
| M (ma, deg) |
0.001485 |
Magnitude
Scatter + Global Linear
$$
M_a = (-1.455 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
-1.455 |
| n |
6.000 |
| gf |
0.999 |
| gb |
-0.869 |
| k |
1.000 |
| 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) |
| 2026-09-20 00:00 |
03:23:24.46 |
+41:15:22.8 |
HIP 15791 |
3.18 |
| 2026-09-20 12:00 |
03:23:22.25 |
+41:15:36.1 |
HIP 15791 |
3.55 |
| 2026-09-21 00:00 |
03:23:20.01 |
+41:15:49.3 |
HIP 15791 |
3.94 |
| 2026-09-21 12:00 |
03:23:17.74 |
+41:16:02.3 |
HIP 15791 |
4.35 |
| 2026-09-22 00:00 |
03:23:15.44 |
+41:16:15.1 |
HIP 15791 |
4.77 |
| 2026-09-22 12:00 |
03:23:13.11 |
+41:16:27.8 |
HIP 15791 |
5.21 |
| 2026-09-23 00:00 |
03:23:10.76 |
+41:16:40.3 |
HIP 15791 |
5.66 |
| 2026-09-23 12:00 |
03:23:08.37 |
+41:16:52.7 |
HIP 15791 |
6.11 |
| 2026-09-24 00:00 |
03:23:05.97 |
+41:17:04.9 |
HIP 15726 |
6.36 |
| 2026-09-24 12:00 |
03:23:03.53 |
+41:17:16.9 |
HIP 15726 |
5.86 |
| 2026-09-25 00:00 |
03:23:01.06 |
+41:17:28.8 |
HIP 15726 |
5.36 |
| 2026-09-25 12:00 |
03:22:58.57 |
+41:17:40.5 |
HIP 15726 |
4.86 |
| 2026-09-26 00:00 |
03:22:56.05 |
+41:17:52.0 |
HIP 15726 |
4.35 |
| 2026-09-26 12:00 |
03:22:53.51 |
+41:18:03.4 |
HIP 15726 |
3.84 |
| 2026-09-27 00:00 |
03:22:50.94 |
+41:18:14.6 |
HIP 15726 |
3.33 |
| 2026-09-27 12:00 |
03:22:48.34 |
+41:18:25.6 |
HIP 15726 |
2.81 |
| 2026-09-28 00:00 |
03:22:45.71 |
+41:18:36.5 |
HIP 15726 |
2.30 |
| 2026-09-28 12:00 |
03:22:43.06 |
+41:18:47.2 |
HIP 15726 |
1.80 |
| 2026-09-29 00:00 |
03:22:40.38 |
+41:18:57.7 |
HIP 15726 |
1.31 |
| 2026-09-29 12:00 |
03:22:37.68 |
+41:19:08.1 |
HIP 15726 |
0.87 |
| 2026-09-30 00:00 |
03:22:34.95 |
+41:19:18.3 |
HIP 15726 |
0.63 |
| 2026-09-30 12:00 |
03:22:32.20 |
+41:19:28.3 |
HIP 15726 |
0.79 |
| 2026-10-01 00:00 |
03:22:29.42 |
+41:19:38.1 |
HIP 15726 |
1.20 |
| 2026-10-01 12:00 |
03:22:26.62 |
+41:19:47.8 |
HIP 15726 |
1.70 |
| 2026-10-02 00:00 |
03:22:23.79 |
+41:19:57.3 |
HIP 15726 |
2.23 |
| 2026-10-02 12:00 |
03:22:20.93 |
+41:20:06.6 |
HIP 15726 |
2.77 |
| 2026-10-03 00:00 |
03:22:18.05 |
+41:20:15.7 |
HIP 15726 |
3.32 |
| 2026-10-03 12:00 |
03:22:15.15 |
+41:20:24.7 |
HIP 15726 |
3.88 |
| 2026-10-04 00:00 |
03:22:12.22 |
+41:20:33.5 |
HIP 15726 |
4.44 |
| 2026-10-04 12:00 |
03:22:09.27 |
+41:20:42.1 |
HIP 15726 |
5.01 |
| 2026-10-05 00:00 |
03:22:06.30 |
+41:20:50.5 |
HIP 15726 |
5.58 |
| 2026-10-05 12:00 |
03:22:03.30 |
+41:20:58.7 |
HIP 15726 |
6.16 |
| 2026-10-06 00:00 |
03:22:00.28 |
+41:21:06.8 |
HIP 15726 |
6.74 |
| 2026-10-06 12:00 |
03:21:57.23 |
+41:21:14.7 |
HIP 15726 |
7.33 |
| 2026-10-07 00:00 |
03:21:54.16 |
+41:21:22.4 |
HIP 15726 |
7.92 |
| 2026-10-07 12:00 |
03:21:51.07 |
+41:21:29.9 |
HIP 15726 |
8.51 |
| 2026-10-08 00:00 |
03:21:47.96 |
+41:21:37.2 |
HIP 15726 |
9.11 |
| 2026-10-08 12:00 |
03:21:44.82 |
+41:21:44.4 |
HIP 15726 |
9.71 |
| 2026-10-09 00:00 |
03:21:41.67 |
+41:21:51.4 |
HIP 15726 |
10.31 |
| 2026-10-09 12:00 |
03:21:38.49 |
+41:21:58.2 |
HIP 15726 |
10.92 |
| 2026-10-10 00:00 |
03:21:35.29 |
+41:22:04.8 |
HIP 15726 |
11.53 |
| 2026-10-10 12:00 |
03:21:32.06 |
+41:22:11.2 |
HIP 15726 |
12.14 |
| 2026-10-11 00:00 |
03:21:28.82 |
+41:22:17.4 |
HIP 15726 |
12.76 |