| 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) |
| 2026-06-01 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 |
| 2026-06-02 12:00 |
20:15:52.99 |
+69:15:04.4 |
HIP 99922 |
3.14 |
| 2026-06-03 00:00 |
20:15:45.28 |
+69:15:57.9 |
HIP 99922 |
4.16 |
| 2026-06-03 12:00 |
20:15:37.48 |
+69:16:50.9 |
HIP 99922 |
5.23 |
| 2026-06-04 00:00 |
20:15:29.57 |
+69:17:43.5 |
HIP 99922 |
6.31 |
| 2026-06-04 12:00 |
20:15:21.58 |
+69:18:35.7 |
HIP 99922 |
7.41 |
| 2026-06-05 00:00 |
20:15:13.48 |
+69:19:27.4 |
HIP 99922 |
8.52 |
| 2026-06-05 12:00 |
20:15:05.29 |
+69:20:18.7 |
HIP 99922 |
9.63 |
| 2026-06-06 00:00 |
20:14:57.01 |
+69:21:09.6 |
HIP 99922 |
10.74 |
| 2026-06-06 12:00 |
20:14:48.63 |
+69:22:00.0 |
HIP 99922 |
11.85 |
| 2026-06-07 00:00 |
20:14:40.16 |
+69:22:49.9 |
HIP 99922 |
12.97 |
| 2026-06-07 12:00 |
20:14:31.59 |
+69:23:39.4 |
HIP 99922 |
14.08 |
| 2026-06-08 00:00 |
20:14:22.93 |
+69:24:28.4 |
HIP 99922 |
15.20 |
| 2026-06-08 12:00 |
20:14:14.18 |
+69:25:17.0 |
HIP 99922 |
16.31 |
| 2026-06-09 00:00 |
20:14:05.34 |
+69:26:05.1 |
HIP 99922 |
17.43 |
| 2026-06-09 12:00 |
20:13:56.40 |
+69:26:52.7 |
HIP 99922 |
18.55 |
| 2026-06-10 00:00 |
20:13:47.38 |
+69:27:39.8 |
HIP 99922 |
19.66 |
| 2026-06-10 12:00 |
20:13:38.27 |
+69:28:26.4 |
HIP 99922 |
20.78 |
| 2026-06-11 00:00 |
20:13:29.06 |
+69:29:12.6 |
HIP 99922 |
21.89 |
| 2026-06-11 12:00 |
20:13:19.77 |
+69:29:58.2 |
HIP 99922 |
23.00 |
| 2026-06-12 00:00 |
20:13:10.40 |
+69:30:43.4 |
HIP 99475 |
22.74 |
| 2026-06-12 12:00 |
20:13:00.93 |
+69:31:28.0 |
HIP 99475 |
21.72 |
| 2026-06-13 00:00 |
20:12:51.38 |
+69:32:12.1 |
HIP 99475 |
20.71 |
| 2026-06-13 12:00 |
20:12:41.74 |
+69:32:55.8 |
HIP 99475 |
19.72 |
| 2026-06-14 00:00 |
20:12:32.02 |
+69:33:38.9 |
HIP 99475 |
18.75 |
| 2026-06-14 12:00 |
20:12:22.22 |
+69:34:21.5 |
HIP 99475 |
17.80 |
| 2026-06-15 00:00 |
20:12:12.33 |
+69:35:03.5 |
HIP 99475 |
16.88 |
| 2026-06-15 12:00 |
20:12:02.37 |
+69:35:45.0 |
HIP 99475 |
15.99 |
| 2026-06-16 00:00 |
20:11:52.32 |
+69:36:26.0 |
HIP 99475 |
15.13 |
| 2026-06-16 12:00 |
20:11:42.19 |
+69:37:06.5 |
HIP 99475 |
14.32 |
| 2026-06-17 00:00 |
20:11:31.98 |
+69:37:46.4 |
HIP 99475 |
13.55 |
| 2026-06-17 12:00 |
20:11:21.69 |
+69:38:25.7 |
HIP 99475 |
12.85 |
| 2026-06-18 00:00 |
20:11:11.33 |
+69:39:04.5 |
HIP 99475 |
12.21 |
| 2026-06-18 12:00 |
20:11:00.89 |
+69:39:42.8 |
HIP 99475 |
11.66 |
| 2026-06-19 00:00 |
20:10:50.38 |
+69:40:20.4 |
HIP 99475 |
11.19 |
| 2026-06-19 12:00 |
20:10:39.79 |
+69:40:57.6 |
HIP 99475 |
10.84 |
| 2026-06-20 00:00 |
20:10:29.13 |
+69:41:34.1 |
HIP 99475 |
10.59 |
| 2026-06-20 12:00 |
20:10:18.40 |
+69:42:10.1 |
HIP 99475 |
10.47 |
| 2026-06-21 00:00 |
20:10:07.59 |
+69:42:45.5 |
HIP 99475 |
10.48 |
| 2026-06-21 12:00 |
20:09:56.72 |
+69:43:20.4 |
HIP 99475 |
10.61 |
| 2026-06-22 00:00 |
20:09:45.78 |
+69:43:54.7 |
HIP 99475 |
10.86 |