208P/McMillan
| Parameter |
Value |
| Designation |
208P/McMillan |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2016-07-02T01:58:31.463040Z |
| Orbit solution date (soln_date, UTC) |
2025-10-28T16:12:51Z |
| Obs used |
402 |
| NEO |
- |
| M1 |
16.100 |
| K1 |
4.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2014-08-19.0000000 |
| e |
0.37204667 |
| q (au) |
2.543028 |
| a (au) |
4.049708 |
| i (deg) |
4.409401 |
| Ω (om, deg) |
36.427937 |
| ω (w, deg) |
310.603963 |
| M (ma, deg) |
277.388305 |
Magnitude
Scatter + Global Linear
$$
M_a = (14.986 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
14.986 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-0.533 |
| 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
Finding Chart
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
05:30:39.09 |
+27:50:58.4 |
HIP 25871 |
10.79 |
| 2026-02-03 12:00 |
05:30:33.05 |
+27:50:33.3 |
HIP 25871 |
11.84 |
| 2026-02-04 00:00 |
05:30:27.33 |
+27:50:08.3 |
HIP 25871 |
12.89 |
| 2026-02-04 12:00 |
05:30:21.91 |
+27:49:43.4 |
HIP 25871 |
13.92 |
| 2026-02-05 00:00 |
05:30:16.79 |
+27:49:18.5 |
HIP 25871 |
14.92 |
| 2026-02-05 12:00 |
05:30:11.98 |
+27:48:53.6 |
HIP 25871 |
15.89 |
| 2026-02-06 00:00 |
05:30:07.48 |
+27:48:28.9 |
HIP 25871 |
16.81 |
| 2026-02-06 12:00 |
05:30:03.29 |
+27:48:04.2 |
HIP 25871 |
17.68 |
| 2026-02-07 00:00 |
05:29:59.40 |
+27:47:39.6 |
HIP 25871 |
18.49 |
| 2026-02-07 12:00 |
05:29:55.82 |
+27:47:15.1 |
HIP 25871 |
19.26 |
| 2026-02-08 00:00 |
05:29:52.55 |
+27:46:50.7 |
HIP 25871 |
19.96 |
| 2026-02-08 12:00 |
05:29:49.58 |
+27:46:26.5 |
HIP 25871 |
20.61 |
| 2026-02-09 00:00 |
05:29:46.91 |
+27:46:02.3 |
HIP 25871 |
21.20 |
| 2026-02-09 12:00 |
05:29:44.55 |
+27:45:38.2 |
HIP 25871 |
21.73 |
| 2026-02-10 00:00 |
05:29:42.49 |
+27:45:14.3 |
HIP 25871 |
22.19 |
| 2026-02-10 12:00 |
05:29:40.74 |
+27:44:50.5 |
HIP 25871 |
22.60 |
| 2026-02-11 00:00 |
05:29:39.29 |
+27:44:26.8 |
HIP 25871 |
22.95 |
| 2026-02-11 12:00 |
05:29:38.15 |
+27:44:03.2 |
HIP 25871 |
23.23 |
| 2026-02-12 00:00 |
05:29:37.30 |
+27:43:39.8 |
HIP 25871 |
23.46 |
| 2026-02-12 12:00 |
05:29:36.76 |
+27:43:16.6 |
HIP 25871 |
23.62 |
| 2026-02-13 00:00 |
05:29:36.52 |
+27:42:53.4 |
HIP 25871 |
23.73 |
| 2026-02-13 12:00 |
05:29:36.58 |
+27:42:30.4 |
HIP 25871 |
23.77 |
| 2026-02-14 00:00 |
05:29:36.94 |
+27:42:07.6 |
HIP 25871 |
23.75 |
| 2026-02-14 12:00 |
05:29:37.61 |
+27:41:45.0 |
HIP 25871 |
23.68 |
| 2026-02-15 00:00 |
05:29:38.56 |
+27:41:22.4 |
HIP 25871 |
23.54 |
| 2026-02-15 12:00 |
05:29:39.82 |
+27:41:00.1 |
HIP 25871 |
23.35 |
| 2026-02-16 00:00 |
05:29:41.37 |
+27:40:37.9 |
HIP 25871 |
23.10 |
| 2026-02-16 12:00 |
05:29:43.22 |
+27:40:15.9 |
HIP 25871 |
22.79 |
| 2026-02-17 00:00 |
05:29:45.37 |
+27:39:54.1 |
HIP 25871 |
22.44 |
| 2026-02-17 12:00 |
05:29:47.81 |
+27:39:32.4 |
HIP 25871 |
22.02 |
| 2026-02-18 00:00 |
05:29:50.54 |
+27:39:10.9 |
HIP 25871 |
21.56 |
| 2026-02-18 12:00 |
05:29:53.57 |
+27:38:49.5 |
HIP 25871 |
21.05 |
| 2026-02-19 00:00 |
05:29:56.88 |
+27:38:28.4 |
HIP 25871 |
20.49 |
| 2026-02-19 12:00 |
05:30:00.49 |
+27:38:07.4 |
HIP 25871 |
19.89 |
| 2026-02-20 00:00 |
05:30:04.39 |
+27:37:46.6 |
HIP 25871 |
19.26 |
| 2026-02-20 12:00 |
05:30:08.57 |
+27:37:26.0 |
HIP 25871 |
18.59 |
| 2026-02-21 00:00 |
05:30:13.04 |
+27:37:05.6 |
HIP 25871 |
17.89 |
| 2026-02-21 12:00 |
05:30:17.79 |
+27:36:45.3 |
HIP 25871 |
17.17 |
| 2026-02-22 00:00 |
05:30:22.83 |
+27:36:25.2 |
HIP 25871 |
16.45 |
| 2026-02-22 12:00 |
05:30:28.15 |
+27:36:05.3 |
HIP 25871 |
15.72 |
| 2026-02-23 00:00 |
05:30:33.75 |
+27:35:45.6 |
HIP 25871 |
15.02 |
| 2026-02-23 12:00 |
05:30:39.63 |
+27:35:26.1 |
HIP 25871 |
14.35 |
| 2026-02-24 00:00 |
05:30:45.79 |
+27:35:06.8 |
HIP 25871 |
13.74 |