| 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) |
| 2026-03-26 00:00 |
05:44:24.42 |
+27:20:14.3 |
HIP 27071 |
6.49 |
| 2026-03-26 12:00 |
05:44:44.58 |
+27:20:02.0 |
HIP 27071 |
7.28 |
| 2026-03-27 00:00 |
05:45:04.93 |
+27:19:49.8 |
HIP 27071 |
10.23 |
| 2026-03-27 12:00 |
05:45:25.46 |
+27:19:37.5 |
HIP 27071 |
14.09 |
| 2026-03-28 00:00 |
05:45:46.16 |
+27:19:25.2 |
HIP 27071 |
18.31 |
| 2026-03-28 12:00 |
05:46:07.04 |
+27:19:13.0 |
HIP 27071 |
22.72 |
| 2026-03-29 00:00 |
05:46:28.09 |
+27:19:00.7 |
HIP 27071 |
27.25 |
| 2026-03-29 12:00 |
05:46:49.31 |
+27:18:48.4 |
HIP 27456 |
26.75 |
| 2026-03-30 00:00 |
05:47:10.71 |
+27:18:36.1 |
HIP 27456 |
22.06 |
| 2026-03-30 12:00 |
05:47:32.27 |
+27:18:23.7 |
HIP 27456 |
17.38 |
| 2026-03-31 00:00 |
05:47:54.00 |
+27:18:11.4 |
HIP 27456 |
12.74 |
| 2026-03-31 12:00 |
05:48:15.90 |
+27:17:59.0 |
HIP 27456 |
8.29 |
| 2026-04-01 00:00 |
05:48:37.96 |
+27:17:46.5 |
HIP 27456 |
4.73 |
| 2026-04-01 12:00 |
05:49:00.19 |
+27:17:34.0 |
HIP 27456 |
4.93 |
| 2026-04-02 00:00 |
05:49:22.58 |
+27:17:21.5 |
HIP 27456 |
8.69 |
| 2026-04-02 12:00 |
05:49:45.12 |
+27:17:09.0 |
HIP 27527 |
9.83 |
| 2026-04-03 00:00 |
05:50:07.83 |
+27:16:56.3 |
HIP 27527 |
10.80 |
| 2026-04-03 12:00 |
05:50:30.70 |
+27:16:43.7 |
HIP 27605 |
13.73 |
| 2026-04-04 00:00 |
05:50:53.72 |
+27:16:30.9 |
HIP 27605 |
14.13 |
| 2026-04-04 12:00 |
05:51:16.89 |
+27:16:18.1 |
HIP 27605 |
16.25 |
| 2026-04-05 00:00 |
05:51:40.22 |
+27:16:05.2 |
HIP 27605 |
19.55 |
| 2026-04-05 12:00 |
05:52:03.70 |
+27:15:52.3 |
HIP 27817 |
19.70 |
| 2026-04-06 00:00 |
05:52:27.34 |
+27:15:39.3 |
HIP 27817 |
16.01 |
| 2026-04-06 12:00 |
05:52:51.12 |
+27:15:26.2 |
HIP 27817 |
13.40 |
| 2026-04-07 00:00 |
05:53:15.05 |
+27:15:13.0 |
HIP 27817 |
12.61 |
| 2026-04-07 12:00 |
05:53:39.13 |
+27:14:59.7 |
HIP 27817 |
13.98 |
| 2026-04-08 00:00 |
05:54:03.35 |
+27:14:46.3 |
HIP 27982 |
14.60 |
| 2026-04-08 12:00 |
05:54:27.72 |
+27:14:32.8 |
HIP 27982 |
9.99 |
| 2026-04-09 00:00 |
05:54:52.24 |
+27:14:19.3 |
HIP 27982 |
6.71 |
| 2026-04-09 12:00 |
05:55:16.89 |
+27:14:05.6 |
HIP 27982 |
7.07 |
| 2026-04-10 00:00 |
05:55:41.69 |
+27:13:51.8 |
HIP 27982 |
10.75 |
| 2026-04-10 12:00 |
05:56:06.63 |
+27:13:37.9 |
HIP 28164 |
14.15 |
| 2026-04-11 00:00 |
05:56:31.70 |
+27:13:23.8 |
HIP 28164 |
9.38 |
| 2026-04-11 12:00 |
05:56:56.91 |
+27:13:09.7 |
HIP 28164 |
6.15 |
| 2026-04-12 00:00 |
05:57:22.26 |
+27:12:55.4 |
HIP 28164 |
7.12 |
| 2026-04-12 12:00 |
05:57:47.75 |
+27:12:41.0 |
HIP 28164 |
11.31 |
| 2026-04-13 00:00 |
05:58:13.36 |
+27:12:26.4 |
HIP 28164 |
16.43 |
| 2026-04-13 12:00 |
05:58:39.11 |
+27:12:11.8 |
HIP 28417 |
19.76 |
| 2026-04-14 00:00 |
05:59:04.99 |
+27:11:56.9 |
HIP 28417 |
14.26 |
| 2026-04-14 12:00 |
05:59:31.01 |
+27:11:41.9 |
HIP 28417 |
9.07 |
| 2026-04-15 00:00 |
05:59:57.15 |
+27:11:26.8 |
HIP 28417 |
5.28 |
| 2026-04-15 12:00 |
06:00:23.41 |
+27:11:11.5 |
HIP 28417 |
6.44 |
| 2026-04-16 00:00 |
06:00:49.81 |
+27:10:56.1 |
HIP 28528 |
8.69 |