| Parameter |
Value |
| Designation |
421P/McNaught |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2009-09-09T00:24:44.127360Z |
| Orbit solution date (soln_date, UTC) |
2023-04-24T23:44:12Z |
| Obs used |
96 |
| NEO |
- |
| M1 |
13.700 |
| K1 |
13.250 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2010-11-09.0000000 |
| e |
0.67538400 |
| q (au) |
1.649202 |
| a (au) |
5.080472 |
| i (deg) |
10.094478 |
| Ω (om, deg) |
55.683595 |
| ω (w, deg) |
259.900711 |
| M (ma, deg) |
36.664020 |
Magnitude
Scatter + Global Linear
$$
M_a = (18.549 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
18.549 |
| n |
2.000 |
| gf |
0.986 |
| gb |
-0.500 |
| k |
0.830 |
| δ90 |
7.395 |
| 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 |
09:36:58.32 |
+23:48:54.6 |
HIP 47258 |
20.11 |
| 2026-09-20 12:00 |
09:37:11.57 |
+23:48:12.7 |
HIP 47258 |
18.85 |
| 2026-09-21 00:00 |
09:37:24.76 |
+23:47:31.1 |
HIP 47258 |
18.03 |
| 2026-09-21 12:00 |
09:37:37.91 |
+23:46:50.0 |
HIP 47288 |
16.20 |
| 2026-09-22 00:00 |
09:37:51.00 |
+23:46:09.3 |
HIP 47288 |
14.28 |
| 2026-09-22 12:00 |
09:38:04.04 |
+23:45:29.0 |
HIP 47288 |
12.84 |
| 2026-09-23 00:00 |
09:38:17.02 |
+23:44:49.1 |
HIP 47288 |
12.03 |
| 2026-09-23 12:00 |
09:38:29.94 |
+23:44:09.6 |
HIP 47288 |
11.96 |
| 2026-09-24 00:00 |
09:38:42.81 |
+23:43:30.5 |
HIP 47288 |
12.64 |
| 2026-09-24 12:00 |
09:38:55.62 |
+23:42:51.9 |
HIP 47288 |
13.95 |
| 2026-09-25 00:00 |
09:39:08.38 |
+23:42:13.7 |
HIP 47288 |
15.72 |
| 2026-09-25 12:00 |
09:39:21.08 |
+23:41:36.0 |
HIP 47288 |
17.82 |
| 2026-09-26 00:00 |
09:39:33.72 |
+23:40:58.7 |
HIP 47288 |
20.13 |
| 2026-09-26 12:00 |
09:39:46.30 |
+23:40:21.8 |
HIP 47288 |
22.58 |
| 2026-09-27 00:00 |
09:39:58.82 |
+23:39:45.3 |
HIP 47288 |
25.13 |
| 2026-09-27 12:00 |
09:40:11.28 |
+23:39:09.3 |
HIP 47288 |
27.74 |
| 2026-09-28 00:00 |
09:40:23.68 |
+23:38:33.8 |
HIP 47576 |
29.46 |
| 2026-09-28 12:00 |
09:40:36.02 |
+23:37:58.7 |
HIP 47576 |
26.94 |
| 2026-09-29 00:00 |
09:40:48.30 |
+23:37:24.1 |
HIP 47576 |
24.52 |
| 2026-09-29 12:00 |
09:41:00.51 |
+23:36:49.9 |
HIP 47576 |
22.23 |
| 2026-09-30 00:00 |
09:41:12.66 |
+23:36:16.2 |
HIP 47576 |
20.09 |
| 2026-09-30 12:00 |
09:41:24.75 |
+23:35:42.9 |
HIP 47576 |
18.17 |
| 2026-10-01 00:00 |
09:41:36.78 |
+23:35:10.1 |
HIP 47576 |
16.51 |
| 2026-10-01 12:00 |
09:41:48.74 |
+23:34:37.8 |
HIP 47644 |
14.02 |
| 2026-10-02 00:00 |
09:42:00.63 |
+23:34:06.0 |
HIP 47644 |
11.39 |
| 2026-10-02 12:00 |
09:42:12.46 |
+23:33:34.6 |
HIP 47644 |
8.88 |
| 2026-10-03 00:00 |
09:42:24.22 |
+23:33:03.7 |
HIP 47644 |
6.56 |
| 2026-10-03 12:00 |
09:42:35.91 |
+23:32:33.3 |
HIP 47644 |
4.74 |
| 2026-10-04 00:00 |
09:42:47.54 |
+23:32:03.4 |
HIP 47644 |
4.09 |
| 2026-10-04 12:00 |
09:42:59.10 |
+23:31:34.0 |
HIP 47644 |
5.05 |
| 2026-10-05 00:00 |
09:43:10.59 |
+23:31:05.1 |
HIP 47644 |
6.96 |
| 2026-10-05 12:00 |
09:43:22.00 |
+23:30:36.7 |
HIP 47644 |
9.25 |
| 2026-10-06 00:00 |
09:43:33.35 |
+23:30:08.8 |
HIP 47644 |
11.67 |
| 2026-10-06 12:00 |
09:43:44.63 |
+23:29:41.4 |
HIP 47644 |
14.16 |
| 2026-10-07 00:00 |
09:43:55.83 |
+23:29:14.5 |
HIP 47644 |
16.67 |
| 2026-10-07 12:00 |
09:44:06.96 |
+23:28:48.2 |
HIP 47853 |
15.55 |
| 2026-10-08 00:00 |
09:44:18.02 |
+23:28:22.3 |
HIP 47853 |
13.01 |
| 2026-10-08 12:00 |
09:44:29.00 |
+23:27:57.0 |
HIP 47853 |
10.50 |
| 2026-10-09 00:00 |
09:44:39.90 |
+23:27:32.2 |
HIP 47853 |
8.04 |
| 2026-10-09 12:00 |
09:44:50.74 |
+23:27:07.9 |
HIP 47853 |
5.67 |
| 2026-10-10 00:00 |
09:45:01.49 |
+23:26:44.2 |
HIP 47853 |
3.50 |
| 2026-10-10 12:00 |
09:45:12.17 |
+23:26:21.0 |
HIP 47853 |
2.21 |
| 2026-10-11 00:00 |
09:45:22.77 |
+23:25:58.4 |
HIP 47853 |
3.11 |