| 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
$$
M_a = (18.570 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
18.570 |
| n |
2.000 |
| gf |
0.971 |
| gb |
-0.500 |
| k |
0.825 |
| δ90 |
7.163 |
| 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 |
08:38:58.71 |
+28:18:03.0 |
HIP 42294 |
21.27 |
| 2026-05-12 12:00 |
08:39:05.05 |
+28:17:09.8 |
HIP 42294 |
22.67 |
| 2026-05-13 00:00 |
08:39:11.50 |
+28:16:16.3 |
HIP 42294 |
24.13 |
| 2026-05-13 12:00 |
08:39:18.06 |
+28:15:22.6 |
HIP 42294 |
25.63 |
| 2026-05-14 00:00 |
08:39:24.72 |
+28:14:28.6 |
HIP 42577 |
26.32 |
| 2026-05-14 12:00 |
08:39:31.49 |
+28:13:34.4 |
HIP 42577 |
26.09 |
| 2026-05-15 00:00 |
08:39:38.37 |
+28:12:39.9 |
HIP 42577 |
25.96 |
| 2026-05-15 12:00 |
08:39:45.36 |
+28:11:45.1 |
HIP 42577 |
25.94 |
| 2026-05-16 00:00 |
08:39:52.45 |
+28:10:50.1 |
HIP 42577 |
26.04 |
| 2026-05-16 12:00 |
08:39:59.64 |
+28:09:54.8 |
HIP 42577 |
26.26 |
| 2026-05-17 00:00 |
08:40:06.94 |
+28:08:59.3 |
HIP 42577 |
26.60 |
| 2026-05-17 12:00 |
08:40:14.35 |
+28:08:03.6 |
HIP 42577 |
27.06 |
| 2026-05-18 00:00 |
08:40:21.85 |
+28:07:07.6 |
HIP 42710 |
27.42 |
| 2026-05-18 12:00 |
08:40:29.46 |
+28:06:11.3 |
HIP 42710 |
25.51 |
| 2026-05-19 00:00 |
08:40:37.17 |
+28:05:14.9 |
HIP 42710 |
23.58 |
| 2026-05-19 12:00 |
08:40:44.98 |
+28:04:18.2 |
HIP 42710 |
21.62 |
| 2026-05-20 00:00 |
08:40:52.89 |
+28:03:21.2 |
HIP 42710 |
19.65 |
| 2026-05-20 12:00 |
08:41:00.89 |
+28:02:24.1 |
HIP 42710 |
17.66 |
| 2026-05-21 00:00 |
08:41:09.00 |
+28:01:26.7 |
HIP 42710 |
15.64 |
| 2026-05-21 12:00 |
08:41:17.21 |
+28:00:29.1 |
HIP 42710 |
13.62 |
| 2026-05-22 00:00 |
08:41:25.51 |
+27:59:31.3 |
HIP 42710 |
11.57 |
| 2026-05-22 12:00 |
08:41:33.91 |
+27:58:33.2 |
HIP 42710 |
9.52 |
| 2026-05-23 00:00 |
08:41:42.40 |
+27:57:35.0 |
HIP 42710 |
7.47 |
| 2026-05-23 12:00 |
08:41:50.99 |
+27:56:36.5 |
HIP 42710 |
5.44 |
| 2026-05-24 00:00 |
08:41:59.67 |
+27:55:37.9 |
HIP 42710 |
3.51 |
| 2026-05-24 12:00 |
08:42:08.45 |
+27:54:39.0 |
HIP 42710 |
2.06 |
| 2026-05-25 00:00 |
08:42:17.31 |
+27:53:39.9 |
HIP 42710 |
2.38 |
| 2026-05-25 12:00 |
08:42:26.27 |
+27:52:40.6 |
HIP 42710 |
4.10 |
| 2026-05-26 00:00 |
08:42:35.33 |
+27:51:41.2 |
HIP 42710 |
6.16 |
| 2026-05-26 12:00 |
08:42:44.47 |
+27:50:41.5 |
HIP 42710 |
8.33 |
| 2026-05-27 00:00 |
08:42:53.70 |
+27:49:41.7 |
HIP 42710 |
10.55 |
| 2026-05-27 12:00 |
08:43:03.02 |
+27:48:41.6 |
HIP 42710 |
12.81 |
| 2026-05-28 00:00 |
08:43:12.43 |
+27:47:41.4 |
HIP 42710 |
15.09 |
| 2026-05-28 12:00 |
08:43:21.93 |
+27:46:41.0 |
HIP 42710 |
17.40 |
| 2026-05-29 00:00 |
08:43:31.51 |
+27:45:40.4 |
HIP 42710 |
19.74 |
| 2026-05-29 12:00 |
08:43:41.18 |
+27:44:39.6 |
HIP 42710 |
22.09 |
| 2026-05-30 00:00 |
08:43:50.94 |
+27:43:38.7 |
HIP 42710 |
24.47 |
| 2026-05-30 12:00 |
08:44:00.78 |
+27:42:37.6 |
HIP 42710 |
26.86 |
| 2026-05-31 00:00 |
08:44:10.71 |
+27:41:36.3 |
HIP 43048 |
28.00 |
| 2026-05-31 12:00 |
08:44:20.72 |
+27:40:34.8 |
HIP 43048 |
25.63 |
| 2026-06-01 00:00 |
08:44:30.82 |
+27:39:33.1 |
HIP 43048 |
23.25 |
| 2026-06-01 12:00 |
08:44:40.99 |
+27:38:31.3 |
HIP 43048 |
20.86 |
| 2026-06-02 00:00 |
08:44:51.25 |
+27:37:29.4 |
HIP 43048 |
18.49 |