| Parameter |
Value |
| Designation |
C/2018 C2 (Lemmon) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2018-06-02T05:22:27.024960Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:41Z |
| Obs used |
1672 |
| NEO |
- |
| M1 |
7.600 |
| K1 |
26.500 |
| PC |
0.030 |
| Discovery observation (MPC, UTC) |
2018-02-05T13:13:03.072000Z |
| Discovery magnitude (MPC) |
19.60 G |
| Discovery observatory (MPC) |
G96 · University of Arizona Mt. Lemmon Survey |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2018-05-20.0000000 |
| e |
1.00180656 |
| q (au) |
1.956513 |
| a (au) |
-1083.006061 |
| i (deg) |
34.453393 |
| Ω (om, deg) |
91.139716 |
| ω (w, deg) |
134.138488 |
| M (ma, deg) |
-0.000366 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.243 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.243 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.500 |
| 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
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) |
End (UTC) |
a |
b |
| 2018-01-28 |
2018-06-01 |
+12.3467 |
-3.481 |
| 2018-06-02 |
2018-10-27 |
-13.9723 |
+3.855 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-06-01 00:00 |
01:45:35.73 |
-25:01:11.2 |
HIP 8209 |
2.07 |
| 2026-06-01 12:00 |
01:45:40.43 |
-25:01:22.0 |
HIP 8209 |
1.83 |
| 2026-06-02 00:00 |
01:45:45.10 |
-25:01:33.2 |
HIP 8209 |
2.16 |
| 2026-06-02 12:00 |
01:45:49.74 |
-25:01:44.8 |
HIP 8209 |
2.87 |
| 2026-06-03 00:00 |
01:45:54.35 |
-25:01:56.8 |
HIP 8209 |
3.75 |
| 2026-06-03 12:00 |
01:45:58.92 |
-25:02:09.3 |
HIP 8209 |
4.70 |
| 2026-06-04 00:00 |
01:46:03.47 |
-25:02:22.3 |
HIP 8209 |
5.67 |
| 2026-06-04 12:00 |
01:46:07.98 |
-25:02:35.6 |
HIP 8209 |
6.66 |
| 2026-06-05 00:00 |
01:46:12.46 |
-25:02:49.4 |
HIP 8209 |
7.66 |
| 2026-06-05 12:00 |
01:46:16.91 |
-25:03:03.6 |
HIP 8209 |
8.66 |
| 2026-06-06 00:00 |
01:46:21.32 |
-25:03:18.2 |
HIP 8209 |
9.67 |
| 2026-06-06 12:00 |
01:46:25.71 |
-25:03:33.3 |
HIP 8209 |
10.66 |
| 2026-06-07 00:00 |
01:46:30.06 |
-25:03:48.8 |
HIP 8209 |
11.66 |
| 2026-06-07 12:00 |
01:46:34.37 |
-25:04:04.7 |
HIP 8209 |
12.65 |
| 2026-06-08 00:00 |
01:46:38.66 |
-25:04:21.1 |
HIP 8209 |
13.64 |
| 2026-06-08 12:00 |
01:46:42.90 |
-25:04:37.8 |
HIP 8209 |
14.63 |
| 2026-06-09 00:00 |
01:46:47.12 |
-25:04:55.0 |
HIP 8209 |
15.60 |
| 2026-06-09 12:00 |
01:46:51.30 |
-25:05:12.6 |
HIP 8209 |
16.58 |
| 2026-06-10 00:00 |
01:46:55.44 |
-25:05:30.7 |
HIP 8209 |
17.55 |
| 2026-06-10 12:00 |
01:46:59.55 |
-25:05:49.1 |
HIP 8209 |
18.51 |
| 2026-06-11 00:00 |
01:47:03.63 |
-25:06:08.0 |
HIP 8209 |
19.47 |
| 2026-06-11 12:00 |
01:47:07.66 |
-25:06:27.3 |
HIP 8209 |
20.42 |
| 2026-06-12 00:00 |
01:47:11.67 |
-25:06:47.0 |
HIP 8209 |
21.37 |
| 2026-06-12 12:00 |
01:47:15.63 |
-25:07:07.2 |
HIP 8209 |
22.31 |
| 2026-06-13 00:00 |
01:47:19.56 |
-25:07:27.7 |
HIP 8209 |
23.25 |
| 2026-06-13 12:00 |
01:47:23.46 |
-25:07:48.7 |
HIP 8209 |
24.18 |
| 2026-06-14 00:00 |
01:47:27.31 |
-25:08:10.1 |
HIP 8209 |
25.11 |
| 2026-06-14 12:00 |
01:47:31.13 |
-25:08:31.9 |
HIP 8209 |
26.03 |
| 2026-06-15 00:00 |
01:47:34.91 |
-25:08:54.1 |
HIP 8209 |
26.94 |
| 2026-06-15 12:00 |
01:47:38.66 |
-25:09:16.7 |
HIP 8209 |
27.85 |
| 2026-06-16 00:00 |
01:47:42.36 |
-25:09:39.8 |
HIP 8209 |
28.75 |
| 2026-06-16 12:00 |
01:47:46.03 |
-25:10:03.2 |
HIP 8209 |
29.65 |
| 2026-06-17 00:00 |
01:47:49.66 |
-25:10:27.0 |
HIP 8209 |
30.54 |
| 2026-06-17 12:00 |
01:47:53.25 |
-25:10:51.3 |
HIP 8209 |
31.43 |
| 2026-06-18 00:00 |
01:47:56.80 |
-25:11:15.9 |
HIP 8310 |
32.15 |
| 2026-06-18 12:00 |
01:48:00.31 |
-25:11:41.0 |
HIP 8310 |
32.02 |
| 2026-06-19 00:00 |
01:48:03.78 |
-25:12:06.4 |
HIP 8310 |
31.91 |
| 2026-06-19 12:00 |
01:48:07.21 |
-25:12:32.2 |
HIP 8310 |
31.82 |
| 2026-06-20 00:00 |
01:48:10.60 |
-25:12:58.5 |
HIP 8310 |
31.74 |
| 2026-06-20 12:00 |
01:48:13.95 |
-25:13:25.1 |
HIP 8310 |
31.68 |
| 2026-06-21 00:00 |
01:48:17.26 |
-25:13:52.1 |
HIP 8310 |
31.63 |
| 2026-06-21 12:00 |
01:48:20.53 |
-25:14:19.5 |
HIP 8310 |
31.59 |
| 2026-06-22 00:00 |
01:48:23.76 |
-25:14:47.3 |
HIP 8310 |
31.56 |