| Parameter |
Value |
| Designation |
C/1917 F1 (Mellish) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1917-04-11T04:12:43.113600Z |
| Orbit solution date (soln_date, UTC) |
2025-09-09T12:42:30Z |
| Obs used |
12 |
| NEO |
Yes |
| M1 |
10.900 |
| K1 |
15.750 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1917-04-17.0000000 |
| e |
0.99302944 |
| q (au) |
0.190197 |
| a (au) |
27.285690 |
| i (deg) |
32.686283 |
| Ω (om, deg) |
88.675684 |
| ω (w, deg) |
121.313996 |
| M (ma, deg) |
0.040277 |
Magnitude
Scatter + Global Linear
$$
M_a = (9.401 + 5.430\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
9.401 |
| n |
5.430 |
| gf |
0.800 |
| gb |
-1.000 |
| k |
1.000 |
| δ90 |
1.000 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-05-12 00:00 |
02:56:42.41 |
-10:07:43.8 |
HIP 13784 |
14.45 |
| 2026-05-12 12:00 |
02:56:45.00 |
-10:07:34.6 |
HIP 13784 |
14.06 |
| 2026-05-13 00:00 |
02:56:47.59 |
-10:07:25.5 |
HIP 13784 |
13.68 |
| 2026-05-13 12:00 |
02:56:50.18 |
-10:07:16.6 |
HIP 13784 |
13.33 |
| 2026-05-14 00:00 |
02:56:52.76 |
-10:07:07.8 |
HIP 13784 |
13.00 |
| 2026-05-14 12:00 |
02:56:55.34 |
-10:06:59.2 |
HIP 13784 |
12.69 |
| 2026-05-15 00:00 |
02:56:57.93 |
-10:06:50.7 |
HIP 13784 |
12.41 |
| 2026-05-15 12:00 |
02:57:00.50 |
-10:06:42.4 |
HIP 13784 |
12.15 |
| 2026-05-16 00:00 |
02:57:03.08 |
-10:06:34.3 |
HIP 13784 |
11.92 |
| 2026-05-16 12:00 |
02:57:05.65 |
-10:06:26.3 |
HIP 13784 |
11.72 |
| 2026-05-17 00:00 |
02:57:08.22 |
-10:06:18.5 |
HIP 13784 |
11.55 |
| 2026-05-17 12:00 |
02:57:10.79 |
-10:06:10.8 |
HIP 13784 |
11.41 |
| 2026-05-18 00:00 |
02:57:13.36 |
-10:06:03.3 |
HIP 13784 |
11.31 |
| 2026-05-18 12:00 |
02:57:15.92 |
-10:05:56.0 |
HIP 13784 |
11.24 |
| 2026-05-19 00:00 |
02:57:18.47 |
-10:05:48.9 |
HIP 13784 |
11.20 |
| 2026-05-19 12:00 |
02:57:21.03 |
-10:05:41.9 |
HIP 13784 |
11.19 |
| 2026-05-20 00:00 |
02:57:23.58 |
-10:05:35.0 |
HIP 13784 |
11.22 |
| 2026-05-20 12:00 |
02:57:26.12 |
-10:05:28.4 |
HIP 13784 |
11.29 |
| 2026-05-21 00:00 |
02:57:28.66 |
-10:05:21.9 |
HIP 13784 |
11.38 |
| 2026-05-21 12:00 |
02:57:31.20 |
-10:05:15.5 |
HIP 13784 |
11.51 |
| 2026-05-22 00:00 |
02:57:33.73 |
-10:05:09.4 |
HIP 13784 |
11.67 |
| 2026-05-22 12:00 |
02:57:36.25 |
-10:05:03.3 |
HIP 13784 |
11.86 |
| 2026-05-23 00:00 |
02:57:38.78 |
-10:04:57.5 |
HIP 13784 |
12.07 |
| 2026-05-23 12:00 |
02:57:41.29 |
-10:04:51.8 |
HIP 13784 |
12.31 |
| 2026-05-24 00:00 |
02:57:43.80 |
-10:04:46.3 |
HIP 13784 |
12.57 |
| 2026-05-24 12:00 |
02:57:46.31 |
-10:04:41.0 |
HIP 13784 |
12.85 |
| 2026-05-25 00:00 |
02:57:48.81 |
-10:04:35.8 |
HIP 13784 |
13.16 |
| 2026-05-25 12:00 |
02:57:51.30 |
-10:04:30.8 |
HIP 13784 |
13.48 |
| 2026-05-26 00:00 |
02:57:53.79 |
-10:04:26.0 |
HIP 13784 |
13.82 |
| 2026-05-26 12:00 |
02:57:56.27 |
-10:04:21.3 |
HIP 13784 |
14.18 |
| 2026-05-27 00:00 |
02:57:58.74 |
-10:04:16.8 |
HIP 13784 |
14.55 |
| 2026-05-27 12:00 |
02:58:01.21 |
-10:04:12.5 |
HIP 13784 |
14.93 |
| 2026-05-28 00:00 |
02:58:03.67 |
-10:04:08.4 |
HIP 13784 |
15.32 |
| 2026-05-28 12:00 |
02:58:06.13 |
-10:04:04.4 |
HIP 13784 |
15.73 |
| 2026-05-29 00:00 |
02:58:08.58 |
-10:04:00.6 |
HIP 13784 |
16.14 |
| 2026-05-29 12:00 |
02:58:11.02 |
-10:03:56.9 |
HIP 13784 |
16.56 |
| 2026-05-30 00:00 |
02:58:13.45 |
-10:03:53.4 |
HIP 13784 |
16.99 |
| 2026-05-30 12:00 |
02:58:15.88 |
-10:03:50.1 |
HIP 13784 |
17.43 |
| 2026-05-31 00:00 |
02:58:18.30 |
-10:03:47.0 |
HIP 13784 |
17.87 |
| 2026-05-31 12:00 |
02:58:20.71 |
-10:03:44.0 |
HIP 13784 |
18.32 |
| 2026-06-01 00:00 |
02:58:23.11 |
-10:03:41.2 |
HIP 13883 |
18.11 |
| 2026-06-01 12:00 |
02:58:25.50 |
-10:03:38.6 |
HIP 13883 |
17.88 |
| 2026-06-02 00:00 |
02:58:27.89 |
-10:03:36.1 |
HIP 13883 |
17.67 |