| Parameter |
Value |
| Designation |
C/2017 S7 (Lemmon) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2017-05-27T21:16:49.696320Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:36Z |
| Obs used |
157 |
| NEO |
- |
| M1 |
6.700 |
| K1 |
10.000 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2017-11-16.0000000 |
| e |
1.00249982 |
| q (au) |
7.614408 |
| a (au) |
-3045.987574 |
| i (deg) |
124.224743 |
| Ω (om, deg) |
262.788416 |
| ω (w, deg) |
187.747383 |
| M (ma, deg) |
0.001009 |
Magnitude
Scatter + Global Linear
$$
M_a = (1.282 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
1.282 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.505 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-20 00:00 |
23:14:17.00 |
-63:47:55.7 |
HIP 114580 |
11.66 |
| 2026-09-20 12:00 |
23:14:02.02 |
-63:48:01.4 |
HIP 114580 |
10.17 |
| 2026-09-21 00:00 |
23:13:47.06 |
-63:48:06.4 |
HIP 114580 |
8.74 |
| 2026-09-21 12:00 |
23:13:32.14 |
-63:48:10.5 |
HIP 114580 |
7.42 |
| 2026-09-22 00:00 |
23:13:17.24 |
-63:48:13.9 |
HIP 114580 |
6.27 |
| 2026-09-22 12:00 |
23:13:02.36 |
-63:48:16.5 |
HIP 114580 |
5.40 |
| 2026-09-23 00:00 |
23:12:47.52 |
-63:48:18.3 |
HIP 114580 |
4.94 |
| 2026-09-23 12:00 |
23:12:32.72 |
-63:48:19.3 |
HIP 114580 |
5.01 |
| 2026-09-24 00:00 |
23:12:17.94 |
-63:48:19.6 |
HIP 114580 |
5.60 |
| 2026-09-24 12:00 |
23:12:03.20 |
-63:48:19.1 |
HIP 114580 |
6.55 |
| 2026-09-25 00:00 |
23:11:48.50 |
-63:48:17.9 |
HIP 114580 |
7.73 |
| 2026-09-25 12:00 |
23:11:33.83 |
-63:48:15.8 |
HIP 114580 |
9.06 |
| 2026-09-26 00:00 |
23:11:19.20 |
-63:48:13.0 |
HIP 114427 |
9.18 |
| 2026-09-26 12:00 |
23:11:04.61 |
-63:48:09.5 |
HIP 114427 |
8.18 |
| 2026-09-27 00:00 |
23:10:50.06 |
-63:48:05.2 |
HIP 114427 |
7.40 |
| 2026-09-27 12:00 |
23:10:35.56 |
-63:48:00.1 |
HIP 114427 |
6.89 |
| 2026-09-28 00:00 |
23:10:21.09 |
-63:47:54.2 |
HIP 114427 |
6.73 |
| 2026-09-28 12:00 |
23:10:06.67 |
-63:47:47.6 |
HIP 114427 |
6.93 |
| 2026-09-29 00:00 |
23:09:52.29 |
-63:47:40.3 |
HIP 114427 |
7.46 |
| 2026-09-29 12:00 |
23:09:37.96 |
-63:47:32.2 |
HIP 114427 |
8.25 |
| 2026-09-30 00:00 |
23:09:23.68 |
-63:47:23.3 |
HIP 114269 |
7.14 |
| 2026-09-30 12:00 |
23:09:09.45 |
-63:47:13.7 |
HIP 114269 |
6.22 |
| 2026-10-01 00:00 |
23:08:55.27 |
-63:47:03.3 |
HIP 114269 |
5.61 |
| 2026-10-01 12:00 |
23:08:41.13 |
-63:46:52.2 |
HIP 114269 |
5.42 |
| 2026-10-02 00:00 |
23:08:27.05 |
-63:46:40.4 |
HIP 114269 |
5.69 |
| 2026-10-02 12:00 |
23:08:13.03 |
-63:46:27.8 |
HIP 114269 |
6.35 |
| 2026-10-03 00:00 |
23:07:59.05 |
-63:46:14.4 |
HIP 114269 |
7.30 |
| 2026-10-03 12:00 |
23:07:45.14 |
-63:46:00.3 |
HIP 114269 |
8.44 |
| 2026-10-04 00:00 |
23:07:31.28 |
-63:45:45.5 |
HIP 114236 |
9.27 |
| 2026-10-04 12:00 |
23:07:17.47 |
-63:45:29.9 |
HIP 114236 |
9.90 |
| 2026-10-05 00:00 |
23:07:03.73 |
-63:45:13.7 |
HIP 114236 |
10.70 |
| 2026-10-05 12:00 |
23:06:50.04 |
-63:44:56.6 |
HIP 114236 |
11.65 |
| 2026-10-06 00:00 |
23:06:36.42 |
-63:44:38.9 |
HIP 114236 |
12.70 |
| 2026-10-06 12:00 |
23:06:22.86 |
-63:44:20.4 |
HIP 114236 |
13.83 |
| 2026-10-07 00:00 |
23:06:09.37 |
-63:44:01.2 |
HIP 114236 |
15.02 |
| 2026-10-07 12:00 |
23:05:55.93 |
-63:43:41.3 |
HIP 114236 |
16.26 |
| 2026-10-08 00:00 |
23:05:42.57 |
-63:43:20.6 |
HIP 114236 |
17.53 |
| 2026-10-08 12:00 |
23:05:29.27 |
-63:42:59.3 |
HIP 114236 |
18.83 |
| 2026-10-09 00:00 |
23:05:16.04 |
-63:42:37.2 |
HIP 113867 |
19.55 |
| 2026-10-09 12:00 |
23:05:02.88 |
-63:42:14.4 |
HIP 113867 |
19.09 |
| 2026-10-10 00:00 |
23:04:49.79 |
-63:41:50.9 |
HIP 113867 |
18.75 |
| 2026-10-10 12:00 |
23:04:36.77 |
-63:41:26.7 |
HIP 113867 |
18.54 |
| 2026-10-11 00:00 |
23:04:23.82 |
-63:41:01.9 |
HIP 113867 |
18.46 |