| 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
$$
M_a = (14.985 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
14.985 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-0.565 |
| 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) |
| 2026-07-29 00:00 |
07:52:32.65 |
+24:29:23.9 |
HIP 38385 |
22.30 |
| 2026-07-29 12:00 |
07:53:05.02 |
+24:28:05.6 |
HIP 38385 |
27.47 |
| 2026-07-30 00:00 |
07:53:37.34 |
+24:26:47.1 |
HIP 38711 |
26.44 |
| 2026-07-30 12:00 |
07:54:09.62 |
+24:25:28.4 |
HIP 38711 |
18.98 |
| 2026-07-31 00:00 |
07:54:41.86 |
+24:24:09.5 |
HIP 38711 |
11.53 |
| 2026-07-31 12:00 |
07:55:14.05 |
+24:22:50.5 |
HIP 38711 |
4.09 |
| 2026-08-01 00:00 |
07:55:46.19 |
+24:21:31.3 |
HIP 38711 |
3.38 |
| 2026-08-01 12:00 |
07:56:18.29 |
+24:20:12.0 |
HIP 38711 |
10.80 |
| 2026-08-02 00:00 |
07:56:50.35 |
+24:18:52.4 |
HIP 38711 |
18.22 |
| 2026-08-02 12:00 |
07:57:22.35 |
+24:17:32.8 |
HIP 39022 |
23.58 |
| 2026-08-03 00:00 |
07:57:54.31 |
+24:16:12.9 |
HIP 39018 |
16.19 |
| 2026-08-03 12:00 |
07:58:26.23 |
+24:14:52.9 |
HIP 39018 |
8.80 |
| 2026-08-04 00:00 |
07:58:58.09 |
+24:13:32.8 |
HIP 39018 |
1.48 |
| 2026-08-04 12:00 |
07:59:29.90 |
+24:12:12.5 |
HIP 39018 |
5.99 |
| 2026-08-05 00:00 |
08:00:01.67 |
+24:10:52.1 |
HIP 39018 |
13.35 |
| 2026-08-05 12:00 |
08:00:33.39 |
+24:09:31.5 |
HIP 39235 |
19.66 |
| 2026-08-06 00:00 |
08:01:05.05 |
+24:08:10.8 |
HIP 39235 |
14.60 |
| 2026-08-06 12:00 |
08:01:36.67 |
+24:06:49.9 |
HIP 39235 |
12.15 |
| 2026-08-07 00:00 |
08:02:08.23 |
+24:05:29.0 |
HIP 39235 |
13.78 |
| 2026-08-07 12:00 |
08:02:39.74 |
+24:04:07.9 |
HIP 39235 |
18.42 |
| 2026-08-08 00:00 |
08:03:11.19 |
+24:02:46.7 |
HIP 39235 |
24.40 |
| 2026-08-08 12:00 |
08:03:42.60 |
+24:01:25.4 |
HIP 39528 |
22.94 |
| 2026-08-09 00:00 |
08:04:13.95 |
+24:00:03.9 |
HIP 39528 |
20.81 |
| 2026-08-09 12:00 |
08:04:45.24 |
+23:58:42.4 |
HIP 39528 |
21.11 |
| 2026-08-10 00:00 |
08:05:16.48 |
+23:57:20.7 |
HIP 39546 |
21.24 |
| 2026-08-10 12:00 |
08:05:47.66 |
+23:55:59.0 |
HIP 39686 |
17.07 |
| 2026-08-11 00:00 |
08:06:18.78 |
+23:54:37.2 |
HIP 39686 |
14.79 |
| 2026-08-11 12:00 |
08:06:49.85 |
+23:53:15.3 |
HIP 39686 |
15.84 |
| 2026-08-12 00:00 |
08:07:20.86 |
+23:51:53.3 |
HIP 39790 |
11.52 |
| 2026-08-12 12:00 |
08:07:51.81 |
+23:50:31.2 |
HIP 39790 |
10.57 |
| 2026-08-13 00:00 |
08:08:22.69 |
+23:49:09.0 |
HIP 39790 |
13.94 |
| 2026-08-13 12:00 |
08:08:53.52 |
+23:47:46.8 |
HIP 39790 |
19.49 |
| 2026-08-14 00:00 |
08:09:24.28 |
+23:46:24.5 |
HIP 39790 |
25.85 |
| 2026-08-14 12:00 |
08:09:54.99 |
+23:45:02.2 |
HIP 40102 |
27.20 |
| 2026-08-15 00:00 |
08:10:25.63 |
+23:43:39.8 |
HIP 40102 |
20.96 |
| 2026-08-15 12:00 |
08:10:56.20 |
+23:42:17.4 |
HIP 40102 |
15.52 |
| 2026-08-16 00:00 |
08:11:26.71 |
+23:40:54.9 |
HIP 40102 |
12.01 |
| 2026-08-16 12:00 |
08:11:57.16 |
+23:39:32.3 |
HIP 40102 |
12.21 |
| 2026-08-17 00:00 |
08:12:27.54 |
+23:38:09.8 |
HIP 40102 |
15.96 |
| 2026-08-17 12:00 |
08:12:57.85 |
+23:36:47.2 |
HIP 40102 |
21.46 |
| 2026-08-18 00:00 |
08:13:28.10 |
+23:35:24.6 |
HIP 40421 |
24.94 |
| 2026-08-18 12:00 |
08:13:58.28 |
+23:34:01.9 |
HIP 40421 |
19.46 |
| 2026-08-19 00:00 |
08:14:28.39 |
+23:32:39.3 |
HIP 40421 |
15.31 |