| 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
$$
M_a = (15.846 + 4.599\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
15.846 |
| n |
4.599 |
| 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) |
| 2026-07-29 00:00 |
19:54:23.18 |
+69:56:47.1 |
HIP 98333 |
33.43 |
| 2026-07-29 12:00 |
19:54:10.38 |
+69:56:32.4 |
HIP 98333 |
34.34 |
| 2026-07-30 00:00 |
19:53:57.60 |
+69:56:17.1 |
HIP 98333 |
35.26 |
| 2026-07-30 12:00 |
19:53:44.85 |
+69:56:01.2 |
HIP 97433 |
34.82 |
| 2026-07-31 00:00 |
19:53:32.12 |
+69:55:44.5 |
HIP 97433 |
34.11 |
| 2026-07-31 12:00 |
19:53:19.43 |
+69:55:27.2 |
HIP 97433 |
33.43 |
| 2026-08-01 00:00 |
19:53:06.76 |
+69:55:09.2 |
HIP 97433 |
32.78 |
| 2026-08-01 12:00 |
19:52:54.12 |
+69:54:50.6 |
HIP 97433 |
32.17 |
| 2026-08-02 00:00 |
19:52:41.51 |
+69:54:31.3 |
HIP 97433 |
31.59 |
| 2026-08-02 12:00 |
19:52:28.94 |
+69:54:11.3 |
HIP 97433 |
31.05 |
| 2026-08-03 00:00 |
19:52:16.40 |
+69:53:50.7 |
HIP 97433 |
30.55 |
| 2026-08-03 12:00 |
19:52:03.89 |
+69:53:29.4 |
HIP 97433 |
30.10 |
| 2026-08-04 00:00 |
19:51:51.42 |
+69:53:07.5 |
HIP 97433 |
29.69 |
| 2026-08-04 12:00 |
19:51:38.99 |
+69:52:44.9 |
HIP 97263 |
29.01 |
| 2026-08-05 00:00 |
19:51:26.60 |
+69:52:21.6 |
HIP 97263 |
27.99 |
| 2026-08-05 12:00 |
19:51:14.25 |
+69:51:57.7 |
HIP 97263 |
26.98 |
| 2026-08-06 00:00 |
19:51:01.93 |
+69:51:33.2 |
HIP 97263 |
25.99 |
| 2026-08-06 12:00 |
19:50:49.66 |
+69:51:07.9 |
HIP 97263 |
25.01 |
| 2026-08-07 00:00 |
19:50:37.44 |
+69:50:42.1 |
HIP 97263 |
24.05 |
| 2026-08-07 12:00 |
19:50:25.26 |
+69:50:15.6 |
HIP 97263 |
23.12 |
| 2026-08-08 00:00 |
19:50:13.12 |
+69:49:48.4 |
HIP 97263 |
22.21 |
| 2026-08-08 12:00 |
19:50:01.04 |
+69:49:20.6 |
HIP 97263 |
21.33 |
| 2026-08-09 00:00 |
19:49:49.00 |
+69:48:52.2 |
HIP 97263 |
20.48 |
| 2026-08-09 12:00 |
19:49:37.01 |
+69:48:23.1 |
HIP 97263 |
19.66 |
| 2026-08-10 00:00 |
19:49:25.08 |
+69:47:53.4 |
HIP 97263 |
18.89 |
| 2026-08-10 12:00 |
19:49:13.19 |
+69:47:23.0 |
HIP 97263 |
18.16 |
| 2026-08-11 00:00 |
19:49:01.36 |
+69:46:52.0 |
HIP 97263 |
17.49 |
| 2026-08-11 12:00 |
19:48:49.59 |
+69:46:20.4 |
HIP 97263 |
16.87 |
| 2026-08-12 00:00 |
19:48:37.87 |
+69:45:48.1 |
HIP 97263 |
16.32 |
| 2026-08-12 12:00 |
19:48:26.21 |
+69:45:15.3 |
HIP 97263 |
15.85 |
| 2026-08-13 00:00 |
19:48:14.60 |
+69:44:41.8 |
HIP 97263 |
15.45 |
| 2026-08-13 12:00 |
19:48:03.06 |
+69:44:07.6 |
HIP 97263 |
15.15 |
| 2026-08-14 00:00 |
19:47:51.58 |
+69:43:32.9 |
HIP 97263 |
14.93 |
| 2026-08-14 12:00 |
19:47:40.16 |
+69:42:57.6 |
HIP 97263 |
14.81 |
| 2026-08-15 00:00 |
19:47:28.80 |
+69:42:21.6 |
HIP 97263 |
14.80 |
| 2026-08-15 12:00 |
19:47:17.51 |
+69:41:45.0 |
HIP 97263 |
14.88 |
| 2026-08-16 00:00 |
19:47:06.29 |
+69:41:07.8 |
HIP 97263 |
15.06 |
| 2026-08-16 12:00 |
19:46:55.13 |
+69:40:30.1 |
HIP 97263 |
15.33 |
| 2026-08-17 00:00 |
19:46:44.04 |
+69:39:51.7 |
HIP 97263 |
15.70 |
| 2026-08-17 12:00 |
19:46:33.02 |
+69:39:12.7 |
HIP 97263 |
16.15 |
| 2026-08-18 00:00 |
19:46:22.07 |
+69:38:33.2 |
HIP 97263 |
16.68 |
| 2026-08-18 12:00 |
19:46:11.18 |
+69:37:53.0 |
HIP 97041 |
17.19 |
| 2026-08-19 00:00 |
19:46:00.38 |
+69:37:12.3 |
HIP 97041 |
16.04 |