| 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 |
0.998 |
| gb |
-0.721 |
| 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) |
| 2026-03-26 00:00 |
23:36:38.56 |
-58:23:49.6 |
HIP 116570 |
14.81 |
| 2026-03-26 12:00 |
23:36:46.63 |
-58:23:49.0 |
HIP 116570 |
14.42 |
| 2026-03-27 00:00 |
23:36:54.68 |
-58:23:49.1 |
HIP 116570 |
14.11 |
| 2026-03-27 12:00 |
23:37:02.71 |
-58:23:49.8 |
HIP 116570 |
13.89 |
| 2026-03-28 00:00 |
23:37:10.73 |
-58:23:51.1 |
HIP 116570 |
13.75 |
| 2026-03-28 12:00 |
23:37:18.72 |
-58:23:53.0 |
HIP 116612 |
13.54 |
| 2026-03-29 00:00 |
23:37:26.70 |
-58:23:55.6 |
HIP 116612 |
13.22 |
| 2026-03-29 12:00 |
23:37:34.65 |
-58:23:58.8 |
HIP 116612 |
12.99 |
| 2026-03-30 00:00 |
23:37:42.59 |
-58:24:02.7 |
HIP 116612 |
12.85 |
| 2026-03-30 12:00 |
23:37:50.50 |
-58:24:07.2 |
HIP 116612 |
12.80 |
| 2026-03-31 00:00 |
23:37:58.39 |
-58:24:12.3 |
HIP 116612 |
12.85 |
| 2026-03-31 12:00 |
23:38:06.25 |
-58:24:18.1 |
HIP 116612 |
12.99 |
| 2026-04-01 00:00 |
23:38:14.10 |
-58:24:24.4 |
HIP 116612 |
13.22 |
| 2026-04-01 12:00 |
23:38:21.92 |
-58:24:31.5 |
HIP 116612 |
13.54 |
| 2026-04-02 00:00 |
23:38:29.71 |
-58:24:39.1 |
HIP 116612 |
13.93 |
| 2026-04-02 12:00 |
23:38:37.48 |
-58:24:47.4 |
HIP 116612 |
14.40 |
| 2026-04-03 00:00 |
23:38:45.23 |
-58:24:56.3 |
HIP 116612 |
14.93 |
| 2026-04-03 12:00 |
23:38:52.95 |
-58:25:05.9 |
HIP 116612 |
15.52 |
| 2026-04-04 00:00 |
23:39:00.64 |
-58:25:16.1 |
HIP 116612 |
16.17 |
| 2026-04-04 12:00 |
23:39:08.30 |
-58:25:26.9 |
HIP 116612 |
16.85 |
| 2026-04-05 00:00 |
23:39:15.94 |
-58:25:38.4 |
HIP 116612 |
17.58 |
| 2026-04-05 12:00 |
23:39:23.55 |
-58:25:50.5 |
HIP 116612 |
18.33 |
| 2026-04-06 00:00 |
23:39:31.13 |
-58:26:03.2 |
HIP 116612 |
19.12 |
| 2026-04-06 12:00 |
23:39:38.68 |
-58:26:16.5 |
HIP 116612 |
19.94 |
| 2026-04-07 00:00 |
23:39:46.20 |
-58:26:30.5 |
HIP 116612 |
20.78 |
| 2026-04-07 12:00 |
23:39:53.69 |
-58:26:45.2 |
HIP 116959 |
21.02 |
| 2026-04-08 00:00 |
23:40:01.15 |
-58:27:00.4 |
HIP 116959 |
20.01 |
| 2026-04-08 12:00 |
23:40:08.57 |
-58:27:16.3 |
HIP 116959 |
19.01 |
| 2026-04-09 00:00 |
23:40:15.97 |
-58:27:32.9 |
HIP 116959 |
18.00 |
| 2026-04-09 12:00 |
23:40:23.33 |
-58:27:50.0 |
HIP 116959 |
17.00 |
| 2026-04-10 00:00 |
23:40:30.66 |
-58:28:07.8 |
HIP 116959 |
16.01 |
| 2026-04-10 12:00 |
23:40:37.95 |
-58:28:26.3 |
HIP 116959 |
15.01 |
| 2026-04-11 00:00 |
23:40:45.21 |
-58:28:45.3 |
HIP 116959 |
14.03 |
| 2026-04-11 12:00 |
23:40:52.44 |
-58:29:05.0 |
HIP 116959 |
13.04 |
| 2026-04-12 00:00 |
23:40:59.63 |
-58:29:25.4 |
HIP 116959 |
12.06 |
| 2026-04-12 12:00 |
23:41:06.78 |
-58:29:46.3 |
HIP 116959 |
11.10 |
| 2026-04-13 00:00 |
23:41:13.89 |
-58:30:07.9 |
HIP 116959 |
10.14 |
| 2026-04-13 12:00 |
23:41:20.97 |
-58:30:30.2 |
HIP 116959 |
9.19 |
| 2026-04-14 00:00 |
23:41:28.01 |
-58:30:53.0 |
HIP 116959 |
8.26 |
| 2026-04-14 12:00 |
23:41:35.01 |
-58:31:16.5 |
HIP 116959 |
7.35 |
| 2026-04-15 00:00 |
23:41:41.97 |
-58:31:40.7 |
HIP 116959 |
6.47 |
| 2026-04-15 12:00 |
23:41:48.89 |
-58:32:05.4 |
HIP 116959 |
5.64 |
| 2026-04-16 00:00 |
23:41:55.77 |
-58:32:30.8 |
HIP 116959 |
4.88 |