| Parameter |
Value |
| Designation |
C/2012 H2 (McNaught) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2012-05-03T17:33:48.790080Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:32:07Z |
| Obs used |
40 |
| NEO |
- |
| M1 |
15.700 |
| K1 |
10.000 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2012-05-18.0000000 |
| e |
0.89360944 |
| q (au) |
1.716772 |
| a (au) |
16.136509 |
| i (deg) |
92.835585 |
| Ω (om, deg) |
184.135948 |
| ω (w, deg) |
295.901982 |
| M (ma, deg) |
0.216949 |
Magnitude
Scatter + Global Linear
$$
M_a = (15.847 + 4.598\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
15.847 |
| n |
4.598 |
| gf |
1.000 |
| gb |
-0.576 |
| k |
0.800 |
| 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) |
| 2026-05-12 00:00 |
20:19:46.25 |
+68:31:11.1 |
HIP 100261 |
21.70 |
| 2026-05-12 12:00 |
20:19:43.11 |
+68:32:18.2 |
HIP 100261 |
20.62 |
| 2026-05-13 00:00 |
20:19:39.85 |
+68:33:25.2 |
HIP 100261 |
19.54 |
| 2026-05-13 12:00 |
20:19:36.48 |
+68:34:32.0 |
HIP 100261 |
18.48 |
| 2026-05-14 00:00 |
20:19:33.00 |
+68:35:38.5 |
HIP 100261 |
17.43 |
| 2026-05-14 12:00 |
20:19:29.40 |
+68:36:44.8 |
HIP 100261 |
16.41 |
| 2026-05-15 00:00 |
20:19:25.70 |
+68:37:50.9 |
HIP 100261 |
15.41 |
| 2026-05-15 12:00 |
20:19:21.89 |
+68:38:56.7 |
HIP 100261 |
14.43 |
| 2026-05-16 00:00 |
20:19:17.96 |
+68:40:02.3 |
HIP 100261 |
13.50 |
| 2026-05-16 12:00 |
20:19:13.92 |
+68:41:07.7 |
HIP 100261 |
12.60 |
| 2026-05-17 00:00 |
20:19:09.78 |
+68:42:12.8 |
HIP 100261 |
11.76 |
| 2026-05-17 12:00 |
20:19:05.52 |
+68:43:17.6 |
HIP 100261 |
10.98 |
| 2026-05-18 00:00 |
20:19:01.16 |
+68:44:22.2 |
HIP 100261 |
10.28 |
| 2026-05-18 12:00 |
20:18:56.68 |
+68:45:26.5 |
HIP 100261 |
9.67 |
| 2026-05-19 00:00 |
20:18:52.09 |
+68:46:30.5 |
HIP 100261 |
9.18 |
| 2026-05-19 12:00 |
20:18:47.40 |
+68:47:34.3 |
HIP 100261 |
8.82 |
| 2026-05-20 00:00 |
20:18:42.60 |
+68:48:37.7 |
HIP 100261 |
8.61 |
| 2026-05-20 12:00 |
20:18:37.68 |
+68:49:40.9 |
HIP 100261 |
8.56 |
| 2026-05-21 00:00 |
20:18:32.66 |
+68:50:43.7 |
HIP 100261 |
8.67 |
| 2026-05-21 12:00 |
20:18:27.53 |
+68:51:46.3 |
HIP 100261 |
8.93 |
| 2026-05-22 00:00 |
20:18:22.30 |
+68:52:48.5 |
HIP 100261 |
9.34 |
| 2026-05-22 12:00 |
20:18:16.95 |
+68:53:50.5 |
HIP 100261 |
9.87 |
| 2026-05-23 00:00 |
20:18:11.50 |
+68:54:52.1 |
HIP 100261 |
10.51 |
| 2026-05-23 12:00 |
20:18:05.94 |
+68:55:53.4 |
HIP 100261 |
11.23 |
| 2026-05-24 00:00 |
20:18:00.28 |
+68:56:54.4 |
HIP 100261 |
12.02 |
| 2026-05-24 12:00 |
20:17:54.51 |
+68:57:55.0 |
HIP 100261 |
12.87 |
| 2026-05-25 00:00 |
20:17:48.64 |
+68:58:55.3 |
HIP 100261 |
13.77 |
| 2026-05-25 12:00 |
20:17:42.66 |
+68:59:55.3 |
HIP 100261 |
14.71 |
| 2026-05-26 00:00 |
20:17:36.57 |
+69:00:54.9 |
HIP 99922 |
14.35 |
| 2026-05-26 12:00 |
20:17:30.38 |
+69:01:54.1 |
HIP 99922 |
13.22 |
| 2026-05-27 00:00 |
20:17:24.09 |
+69:02:53.0 |
HIP 99922 |
12.09 |
| 2026-05-27 12:00 |
20:17:17.69 |
+69:03:51.6 |
HIP 99922 |
10.96 |
| 2026-05-28 00:00 |
20:17:11.19 |
+69:04:49.8 |
HIP 99922 |
9.84 |
| 2026-05-28 12:00 |
20:17:04.59 |
+69:05:47.6 |
HIP 99922 |
8.72 |
| 2026-05-29 00:00 |
20:16:57.88 |
+69:06:45.0 |
HIP 99922 |
7.60 |
| 2026-05-29 12:00 |
20:16:51.07 |
+69:07:42.1 |
HIP 99922 |
6.50 |
| 2026-05-30 00:00 |
20:16:44.16 |
+69:08:38.8 |
HIP 99922 |
5.40 |
| 2026-05-30 12:00 |
20:16:37.15 |
+69:09:35.1 |
HIP 99922 |
4.33 |
| 2026-05-31 00:00 |
20:16:30.04 |
+69:10:31.0 |
HIP 99922 |
3.29 |
| 2026-05-31 12:00 |
20:16:22.83 |
+69:11:26.5 |
HIP 99922 |
2.35 |
| 2026-06-01 00:00 |
20:16:15.52 |
+69:12:21.6 |
HIP 99922 |
1.66 |
| 2026-06-01 12:00 |
20:16:08.10 |
+69:13:16.3 |
HIP 99922 |
1.60 |
| 2026-06-02 00:00 |
20:16:00.59 |
+69:14:10.5 |
HIP 99922 |
2.22 |