| Parameter |
Value |
| Designation |
318P/McNaught-Hartley |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2015-10-21T00:27:13.642560Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:28:23Z |
| Obs used |
442 |
| NEO |
- |
| M1 |
9.600 |
| K1 |
13.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2012-04-13.0000000 |
| e |
0.67524420 |
| q (au) |
2.445459 |
| a (au) |
7.530148 |
| i (deg) |
17.894853 |
| Ω (om, deg) |
35.754310 |
| ω (w, deg) |
313.177220 |
| M (ma, deg) |
298.659661 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.986 + 4.792\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.986 |
| n |
4.792 |
| gf |
1.000 |
| gb |
-0.500 |
| k |
0.800 |
| δ90 |
2.293 |
| 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 |
11:44:29.44 |
+16:46:04.4 |
HIP 57310 |
24.93 |
| 2026-03-26 12:00 |
11:44:21.16 |
+16:46:41.8 |
HIP 57310 |
25.08 |
| 2026-03-27 00:00 |
11:44:12.89 |
+16:47:18.7 |
HIP 57310 |
25.41 |
| 2026-03-27 12:00 |
11:44:04.64 |
+16:47:55.2 |
HIP 57310 |
25.90 |
| 2026-03-28 00:00 |
11:43:56.41 |
+16:48:31.2 |
HIP 57310 |
26.55 |
| 2026-03-28 12:00 |
11:43:48.20 |
+16:49:06.8 |
HIP 57310 |
27.34 |
| 2026-03-29 00:00 |
11:43:40.01 |
+16:49:41.8 |
HIP 57310 |
28.26 |
| 2026-03-29 12:00 |
11:43:31.84 |
+16:50:16.4 |
HIP 57310 |
29.29 |
| 2026-03-30 00:00 |
11:43:23.69 |
+16:50:50.5 |
HIP 57310 |
30.43 |
| 2026-03-30 12:00 |
11:43:15.57 |
+16:51:24.2 |
HIP 57310 |
31.66 |
| 2026-03-31 00:00 |
11:43:07.46 |
+16:51:57.3 |
HIP 57310 |
32.96 |
| 2026-03-31 12:00 |
11:42:59.39 |
+16:52:30.0 |
HIP 56981 |
31.81 |
| 2026-04-01 00:00 |
11:42:51.33 |
+16:53:02.1 |
HIP 56981 |
29.81 |
| 2026-04-01 12:00 |
11:42:43.30 |
+16:53:33.8 |
HIP 56981 |
27.81 |
| 2026-04-02 00:00 |
11:42:35.30 |
+16:54:05.0 |
HIP 56981 |
25.83 |
| 2026-04-02 12:00 |
11:42:27.33 |
+16:54:35.6 |
HIP 56981 |
23.86 |
| 2026-04-03 00:00 |
11:42:19.38 |
+16:55:05.8 |
HIP 56981 |
21.89 |
| 2026-04-03 12:00 |
11:42:11.46 |
+16:55:35.4 |
HIP 56981 |
19.93 |
| 2026-04-04 00:00 |
11:42:03.58 |
+16:56:04.6 |
HIP 56981 |
17.98 |
| 2026-04-04 12:00 |
11:41:55.72 |
+16:56:33.2 |
HIP 56981 |
16.05 |
| 2026-04-05 00:00 |
11:41:47.89 |
+16:57:01.3 |
HIP 56981 |
14.12 |
| 2026-04-05 12:00 |
11:41:40.10 |
+16:57:28.9 |
HIP 56981 |
12.20 |
| 2026-04-06 00:00 |
11:41:32.34 |
+16:57:56.0 |
HIP 56981 |
10.29 |
| 2026-04-06 12:00 |
11:41:24.61 |
+16:58:22.6 |
HIP 56981 |
8.39 |
| 2026-04-07 00:00 |
11:41:16.92 |
+16:58:48.6 |
HIP 56981 |
6.51 |
| 2026-04-07 12:00 |
11:41:09.26 |
+16:59:14.1 |
HIP 56981 |
4.63 |
| 2026-04-08 00:00 |
11:41:01.63 |
+16:59:39.1 |
HIP 56981 |
2.78 |
| 2026-04-08 12:00 |
11:40:54.05 |
+17:00:03.5 |
HIP 56981 |
1.02 |
| 2026-04-09 00:00 |
11:40:46.50 |
+17:00:27.4 |
HIP 56981 |
1.11 |
| 2026-04-09 12:00 |
11:40:38.99 |
+17:00:50.8 |
HIP 56981 |
2.86 |
| 2026-04-10 00:00 |
11:40:31.51 |
+17:01:13.6 |
HIP 56981 |
4.67 |
| 2026-04-10 12:00 |
11:40:24.08 |
+17:01:35.9 |
HIP 56981 |
6.48 |
| 2026-04-11 00:00 |
11:40:16.69 |
+17:01:57.6 |
HIP 56981 |
8.28 |
| 2026-04-11 12:00 |
11:40:09.33 |
+17:02:18.8 |
HIP 56981 |
10.07 |
| 2026-04-12 00:00 |
11:40:02.02 |
+17:02:39.5 |
HIP 56981 |
11.85 |
| 2026-04-12 12:00 |
11:39:54.76 |
+17:02:59.6 |
HIP 56981 |
13.62 |
| 2026-04-13 00:00 |
11:39:47.53 |
+17:03:19.1 |
HIP 56821 |
13.53 |
| 2026-04-13 12:00 |
11:39:40.35 |
+17:03:38.1 |
HIP 56821 |
11.79 |
| 2026-04-14 00:00 |
11:39:33.21 |
+17:03:56.5 |
HIP 56821 |
10.06 |
| 2026-04-14 12:00 |
11:39:26.12 |
+17:04:14.3 |
HIP 56821 |
8.34 |
| 2026-04-15 00:00 |
11:39:19.08 |
+17:04:31.6 |
HIP 56821 |
6.63 |
| 2026-04-15 12:00 |
11:39:12.08 |
+17:04:48.4 |
HIP 56821 |
4.95 |
| 2026-04-16 00:00 |
11:39:05.13 |
+17:05:04.5 |
HIP 56821 |
3.28 |