| Parameter |
Value |
| Designation |
C/2013 G2 (McNaught) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2012-12-06T08:24:02.825280Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:32:32Z |
| Obs used |
111 |
| NEO |
- |
| M1 |
13.700 |
| K1 |
4.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2013-05-24.0000000 |
| e |
1.00017667 |
| q (au) |
2.154122 |
| a (au) |
-12193.190355 |
| i (deg) |
96.001965 |
| Ω (om, deg) |
274.112530 |
| ω (w, deg) |
293.912193 |
| M (ma, deg) |
0.000123 |
Magnitude
Scatter + Global Linear
$$
M_a = (11.810 + 2.787\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
11.810 |
| n |
2.787 |
| gf |
1.000 |
| gb |
-0.500 |
| k |
1.000 |
| 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) |
| 2026-09-20 00:00 |
17:03:53.37 |
+58:27:32.0 |
HIP 83305 |
19.47 |
| 2026-09-20 12:00 |
17:03:54.65 |
+58:26:39.4 |
HIP 83305 |
19.91 |
| 2026-09-21 00:00 |
17:03:56.00 |
+58:25:46.8 |
HIP 83305 |
20.39 |
| 2026-09-21 12:00 |
17:03:57.41 |
+58:24:54.3 |
HIP 83305 |
20.91 |
| 2026-09-22 00:00 |
17:03:58.88 |
+58:24:02.0 |
HIP 83305 |
21.45 |
| 2026-09-22 12:00 |
17:04:00.41 |
+58:23:09.7 |
HIP 83305 |
22.03 |
| 2026-09-23 00:00 |
17:04:02.00 |
+58:22:17.5 |
HIP 83305 |
22.63 |
| 2026-09-23 12:00 |
17:04:03.65 |
+58:21:25.5 |
HIP 83305 |
23.25 |
| 2026-09-24 00:00 |
17:04:05.36 |
+58:20:33.5 |
HIP 83305 |
23.90 |
| 2026-09-24 12:00 |
17:04:07.13 |
+58:19:41.7 |
HIP 83765 |
24.32 |
| 2026-09-25 00:00 |
17:04:08.95 |
+58:18:50.0 |
HIP 83765 |
23.97 |
| 2026-09-25 12:00 |
17:04:10.84 |
+58:17:58.4 |
HIP 83765 |
23.65 |
| 2026-09-26 00:00 |
17:04:12.78 |
+58:17:07.0 |
HIP 83765 |
23.35 |
| 2026-09-26 12:00 |
17:04:14.78 |
+58:16:15.7 |
HIP 83765 |
23.07 |
| 2026-09-27 00:00 |
17:04:16.84 |
+58:15:24.5 |
HIP 83765 |
22.82 |
| 2026-09-27 12:00 |
17:04:18.96 |
+58:14:33.5 |
HIP 83765 |
22.59 |
| 2026-09-28 00:00 |
17:04:21.13 |
+58:13:42.6 |
HIP 83765 |
22.38 |
| 2026-09-28 12:00 |
17:04:23.37 |
+58:12:51.8 |
HIP 83765 |
22.20 |
| 2026-09-29 00:00 |
17:04:25.66 |
+58:12:01.2 |
HIP 83765 |
22.05 |
| 2026-09-29 12:00 |
17:04:28.00 |
+58:11:10.8 |
HIP 83765 |
21.92 |
| 2026-09-30 00:00 |
17:04:30.41 |
+58:10:20.5 |
HIP 83765 |
21.83 |
| 2026-09-30 12:00 |
17:04:32.87 |
+58:09:30.3 |
HIP 83765 |
21.76 |
| 2026-10-01 00:00 |
17:04:35.39 |
+58:08:40.4 |
HIP 83765 |
21.72 |
| 2026-10-01 12:00 |
17:04:37.96 |
+58:07:50.6 |
HIP 83765 |
21.71 |
| 2026-10-02 00:00 |
17:04:40.59 |
+58:07:01.0 |
HIP 83765 |
21.73 |
| 2026-10-02 12:00 |
17:04:43.28 |
+58:06:11.5 |
HIP 83765 |
21.77 |
| 2026-10-03 00:00 |
17:04:46.02 |
+58:05:22.2 |
HIP 83765 |
21.85 |
| 2026-10-03 12:00 |
17:04:48.81 |
+58:04:33.1 |
HIP 83765 |
21.95 |
| 2026-10-04 00:00 |
17:04:51.67 |
+58:03:44.2 |
HIP 83765 |
22.08 |
| 2026-10-04 12:00 |
17:04:54.57 |
+58:02:55.5 |
HIP 83765 |
22.24 |
| 2026-10-05 00:00 |
17:04:57.54 |
+58:02:07.0 |
HIP 83765 |
22.43 |
| 2026-10-05 12:00 |
17:05:00.55 |
+58:01:18.7 |
HIP 83765 |
22.64 |
| 2026-10-06 00:00 |
17:05:03.63 |
+58:00:30.5 |
HIP 83765 |
22.88 |
| 2026-10-06 12:00 |
17:05:06.75 |
+57:59:42.6 |
HIP 83765 |
23.14 |
| 2026-10-07 00:00 |
17:05:09.93 |
+57:58:54.9 |
HIP 83765 |
23.43 |
| 2026-10-07 12:00 |
17:05:13.16 |
+57:58:07.4 |
HIP 83765 |
23.74 |
| 2026-10-08 00:00 |
17:05:16.45 |
+57:57:20.1 |
HIP 83765 |
24.07 |
| 2026-10-08 12:00 |
17:05:19.79 |
+57:56:33.1 |
HIP 83765 |
24.42 |
| 2026-10-09 00:00 |
17:05:23.18 |
+57:55:46.2 |
HIP 83765 |
24.79 |
| 2026-10-09 12:00 |
17:05:26.63 |
+57:54:59.6 |
HIP 83765 |
25.19 |
| 2026-10-10 00:00 |
17:05:30.12 |
+57:54:13.3 |
HIP 83765 |
25.60 |
| 2026-10-10 12:00 |
17:05:33.67 |
+57:53:27.1 |
HIP 83765 |
26.03 |
| 2026-10-11 00:00 |
17:05:37.27 |
+57:52:41.2 |
HIP 83765 |
26.47 |