| 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 |
0.995 |
| gb |
-0.500 |
| k |
0.800 |
| δ90 |
2.292 |
| 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 |
11:54:11.96 |
+13:02:04.9 |
HIP 57941 |
29.64 |
| 2026-09-20 12:00 |
11:54:21.32 |
+13:01:01.1 |
HIP 57941 |
31.91 |
| 2026-09-21 00:00 |
11:54:30.68 |
+12:59:57.4 |
HIP 57941 |
34.21 |
| 2026-09-21 12:00 |
11:54:40.04 |
+12:58:54.0 |
HIP 57941 |
36.54 |
| 2026-09-22 00:00 |
11:54:49.40 |
+12:57:50.8 |
HIP 58253 |
38.55 |
| 2026-09-22 12:00 |
11:54:58.76 |
+12:56:47.9 |
HIP 58253 |
37.56 |
| 2026-09-23 00:00 |
11:55:08.12 |
+12:55:45.1 |
HIP 58253 |
36.70 |
| 2026-09-23 12:00 |
11:55:17.48 |
+12:54:42.5 |
HIP 58253 |
35.99 |
| 2026-09-24 00:00 |
11:55:26.83 |
+12:53:40.2 |
HIP 58253 |
35.45 |
| 2026-09-24 12:00 |
11:55:36.19 |
+12:52:38.1 |
HIP 58228 |
34.65 |
| 2026-09-25 00:00 |
11:55:45.54 |
+12:51:36.2 |
HIP 58228 |
32.83 |
| 2026-09-25 12:00 |
11:55:54.89 |
+12:50:34.6 |
HIP 58228 |
31.11 |
| 2026-09-26 00:00 |
11:56:04.23 |
+12:49:33.1 |
HIP 58228 |
29.51 |
| 2026-09-26 12:00 |
11:56:13.58 |
+12:48:31.9 |
HIP 58228 |
28.04 |
| 2026-09-27 00:00 |
11:56:22.91 |
+12:47:31.0 |
HIP 58228 |
26.73 |
| 2026-09-27 12:00 |
11:56:32.25 |
+12:46:30.3 |
HIP 58228 |
25.60 |
| 2026-09-28 00:00 |
11:56:41.58 |
+12:45:29.8 |
HIP 58228 |
24.68 |
| 2026-09-28 12:00 |
11:56:50.90 |
+12:44:29.5 |
HIP 58228 |
23.98 |
| 2026-09-29 00:00 |
11:57:00.22 |
+12:43:29.5 |
HIP 58228 |
23.53 |
| 2026-09-29 12:00 |
11:57:09.53 |
+12:42:29.8 |
HIP 58228 |
23.34 |
| 2026-09-30 00:00 |
11:57:18.84 |
+12:41:30.3 |
HIP 58417 |
22.06 |
| 2026-09-30 12:00 |
11:57:28.13 |
+12:40:31.1 |
HIP 58417 |
20.55 |
| 2026-10-01 00:00 |
11:57:37.42 |
+12:39:32.1 |
HIP 58417 |
19.25 |
| 2026-10-01 12:00 |
11:57:46.71 |
+12:38:33.3 |
HIP 58417 |
18.18 |
| 2026-10-02 00:00 |
11:57:55.98 |
+12:37:34.9 |
HIP 58417 |
17.40 |
| 2026-10-02 12:00 |
11:58:05.25 |
+12:36:36.7 |
HIP 58417 |
16.94 |
| 2026-10-03 00:00 |
11:58:14.51 |
+12:35:38.7 |
HIP 58417 |
16.82 |
| 2026-10-03 12:00 |
11:58:23.75 |
+12:34:41.1 |
HIP 58417 |
17.06 |
| 2026-10-04 00:00 |
11:58:32.99 |
+12:33:43.7 |
HIP 58417 |
17.64 |
| 2026-10-04 12:00 |
11:58:42.22 |
+12:32:46.6 |
HIP 58417 |
18.52 |
| 2026-10-05 00:00 |
11:58:51.43 |
+12:31:49.8 |
HIP 58417 |
19.66 |
| 2026-10-05 12:00 |
11:59:00.64 |
+12:30:53.2 |
HIP 58417 |
21.01 |
| 2026-10-06 00:00 |
11:59:09.83 |
+12:29:56.9 |
HIP 58417 |
22.55 |
| 2026-10-06 12:00 |
11:59:19.01 |
+12:29:01.0 |
HIP 58417 |
24.22 |
| 2026-10-07 00:00 |
11:59:28.17 |
+12:28:05.3 |
HIP 58442 |
24.59 |
| 2026-10-07 12:00 |
11:59:37.33 |
+12:27:09.9 |
HIP 58616 |
23.98 |
| 2026-10-08 00:00 |
11:59:46.47 |
+12:26:14.8 |
HIP 58616 |
21.62 |
| 2026-10-08 12:00 |
11:59:55.59 |
+12:25:20.1 |
HIP 58616 |
19.28 |
| 2026-10-09 00:00 |
12:00:04.70 |
+12:24:25.6 |
HIP 58616 |
16.96 |
| 2026-10-09 12:00 |
12:00:13.79 |
+12:23:31.4 |
HIP 58616 |
14.67 |
| 2026-10-10 00:00 |
12:00:22.87 |
+12:22:37.6 |
HIP 58616 |
12.43 |
| 2026-10-10 12:00 |
12:00:31.93 |
+12:21:44.0 |
HIP 58616 |
10.26 |
| 2026-10-11 00:00 |
12:00:40.98 |
+12:20:50.8 |
HIP 58616 |
8.22 |