C/2020 F7 (Lemmon)
| Parameter |
Value |
| Designation |
C/2020 F7 (Lemmon) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2021-11-14T02:39:42.822720Z |
| Orbit solution date (soln_date, UTC) |
2023-12-28T19:42:30Z |
| Obs used |
608 |
| NEO |
- |
| M1 |
6.600 |
| K1 |
10.750 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2020-12-09.0000000 |
| e |
0.99310004 |
| q (au) |
5.331815 |
| a (au) |
772.731657 |
| i (deg) |
93.951702 |
| Ω (om, deg) |
321.886317 |
| ω (w, deg) |
227.985641 |
| M (ma, deg) |
359.984394 |
Magnitude
Scatter + Global Linear
$$
M_a = (2.349 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
2.349 |
| n |
6.000 |
| gf |
0.970 |
| gb |
-0.676 |
| k |
1.000 |
| δ90 |
9.976 |
| 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
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) |
End (UTC) |
a |
b |
| 2020-01-04 |
2021-11-11 |
+4.9500 |
-3.771 |
| 2021-11-14 |
2023-12-20 |
-12.9005 |
+9.601 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
22:45:27.87 |
-45:15:01.4 |
HIP 112337 |
17.91 |
| 2026-02-03 12:00 |
22:45:37.43 |
-45:13:11.0 |
HIP 112467 |
16.59 |
| 2026-02-04 00:00 |
22:45:47.01 |
-45:11:21.2 |
HIP 112467 |
14.14 |
| 2026-02-04 12:00 |
22:45:56.62 |
-45:09:31.9 |
HIP 112467 |
11.71 |
| 2026-02-05 00:00 |
22:46:06.26 |
-45:07:43.1 |
HIP 112467 |
9.31 |
| 2026-02-05 12:00 |
22:46:15.93 |
-45:05:54.9 |
HIP 112467 |
6.97 |
| 2026-02-06 00:00 |
22:46:25.63 |
-45:04:07.3 |
HIP 112467 |
4.77 |
| 2026-02-06 12:00 |
22:46:35.36 |
-45:02:20.2 |
HIP 112467 |
3.03 |
| 2026-02-07 00:00 |
22:46:45.12 |
-45:00:33.7 |
HIP 112467 |
2.79 |
| 2026-02-07 12:00 |
22:46:54.90 |
-44:58:47.7 |
HIP 112467 |
4.31 |
| 2026-02-08 00:00 |
22:47:04.70 |
-44:57:02.3 |
HIP 112515 |
4.00 |
| 2026-02-08 12:00 |
22:47:14.54 |
-44:55:17.5 |
HIP 112515 |
3.40 |
| 2026-02-09 00:00 |
22:47:24.39 |
-44:53:33.3 |
HIP 112515 |
4.38 |
| 2026-02-09 12:00 |
22:47:34.27 |
-44:51:49.6 |
HIP 112515 |
6.23 |
| 2026-02-10 00:00 |
22:47:44.18 |
-44:50:06.5 |
HIP 112515 |
8.39 |
| 2026-02-10 12:00 |
22:47:54.10 |
-44:48:24.0 |
HIP 112515 |
10.67 |
| 2026-02-11 00:00 |
22:48:04.05 |
-44:46:42.1 |
HIP 112515 |
13.01 |
| 2026-02-11 12:00 |
22:48:14.01 |
-44:45:00.8 |
HIP 112663 |
11.82 |
| 2026-02-12 00:00 |
22:48:24.00 |
-44:43:20.1 |
HIP 112663 |
9.38 |
| 2026-02-12 12:00 |
22:48:34.01 |
-44:41:40.0 |
HIP 112663 |
6.96 |
| 2026-02-13 00:00 |
22:48:44.03 |
-44:40:00.5 |
HIP 112663 |
4.57 |
| 2026-02-13 12:00 |
22:48:54.07 |
-44:38:21.5 |
HIP 112663 |
2.27 |
| 2026-02-14 00:00 |
22:49:04.13 |
-44:36:43.2 |
HIP 112663 |
1.12 |
| 2026-02-14 12:00 |
22:49:14.21 |
-44:35:05.5 |
HIP 112663 |
3.02 |
| 2026-02-15 00:00 |
22:49:24.30 |
-44:33:28.5 |
HIP 112663 |
5.36 |
| 2026-02-15 12:00 |
22:49:34.40 |
-44:31:52.0 |
HIP 112735 |
7.11 |
| 2026-02-16 00:00 |
22:49:44.52 |
-44:30:16.2 |
HIP 112735 |
5.00 |
| 2026-02-16 12:00 |
22:49:54.65 |
-44:28:40.9 |
HIP 112735 |
3.33 |
| 2026-02-17 00:00 |
22:50:04.80 |
-44:27:06.4 |
HIP 112735 |
2.97 |
| 2026-02-17 12:00 |
22:50:14.95 |
-44:25:32.4 |
HIP 112735 |
4.25 |
| 2026-02-18 00:00 |
22:50:25.12 |
-44:23:59.1 |
HIP 112735 |
6.23 |
| 2026-02-18 12:00 |
22:50:35.30 |
-44:22:26.4 |
HIP 112735 |
8.43 |
| 2026-02-19 00:00 |
22:50:45.48 |
-44:20:54.3 |
HIP 112735 |
10.70 |
| 2026-02-19 12:00 |
22:50:55.68 |
-44:19:22.9 |
HIP 112735 |
13.01 |
| 2026-02-20 00:00 |
22:51:05.88 |
-44:17:52.2 |
HIP 112735 |
15.34 |
| 2026-02-20 12:00 |
22:51:16.09 |
-44:16:22.0 |
HIP 112735 |
17.68 |
| 2026-02-21 00:00 |
22:51:26.30 |
-44:14:52.6 |
HIP 112735 |
20.01 |
| 2026-02-21 12:00 |
22:51:36.52 |
-44:13:23.8 |
HIP 112735 |
22.35 |
| 2026-02-22 00:00 |
22:51:46.75 |
-44:11:55.6 |
HIP 112885 |
22.06 |
| 2026-02-22 12:00 |
22:51:56.98 |
-44:10:28.1 |
HIP 112885 |
20.86 |
| 2026-02-23 00:00 |
22:52:07.21 |
-44:09:01.3 |
HIP 112885 |
19.88 |
| 2026-02-23 12:00 |
22:52:17.45 |
-44:07:35.1 |
HIP 112885 |
19.15 |
| 2026-02-24 00:00 |
22:52:27.68 |
-44:06:09.6 |
HIP 112885 |
18.69 |