| 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 · 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 |
-0.998 |
| 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) |
| 2026-05-12 00:00 |
01:42:05.82 |
-25:00:01.8 |
HIP 7892 |
9.80 |
| 2026-05-12 12:00 |
01:42:11.51 |
-24:59:54.9 |
HIP 7892 |
10.77 |
| 2026-05-13 00:00 |
01:42:17.18 |
-24:59:48.4 |
HIP 7892 |
11.80 |
| 2026-05-13 12:00 |
01:42:22.84 |
-24:59:42.3 |
HIP 7892 |
12.87 |
| 2026-05-14 00:00 |
01:42:28.47 |
-24:59:36.7 |
HIP 7892 |
13.99 |
| 2026-05-14 12:00 |
01:42:34.09 |
-24:59:31.5 |
HIP 7892 |
15.12 |
| 2026-05-15 00:00 |
01:42:39.68 |
-24:59:26.8 |
HIP 7892 |
16.28 |
| 2026-05-15 12:00 |
01:42:45.26 |
-24:59:22.6 |
HIP 7892 |
17.45 |
| 2026-05-16 00:00 |
01:42:50.81 |
-24:59:18.7 |
HIP 7892 |
18.63 |
| 2026-05-16 12:00 |
01:42:56.35 |
-24:59:15.4 |
HIP 7892 |
19.82 |
| 2026-05-17 00:00 |
01:43:01.86 |
-24:59:12.4 |
HIP 7892 |
21.01 |
| 2026-05-17 12:00 |
01:43:07.35 |
-24:59:09.9 |
HIP 7892 |
22.21 |
| 2026-05-18 00:00 |
01:43:12.82 |
-24:59:07.9 |
HIP 7993 |
22.79 |
| 2026-05-18 12:00 |
01:43:18.27 |
-24:59:06.3 |
HIP 7993 |
23.21 |
| 2026-05-19 00:00 |
01:43:23.69 |
-24:59:05.2 |
HIP 7993 |
23.69 |
| 2026-05-19 12:00 |
01:43:29.09 |
-24:59:04.5 |
HIP 7993 |
24.23 |
| 2026-05-20 00:00 |
01:43:34.47 |
-24:59:04.2 |
HIP 7993 |
24.82 |
| 2026-05-20 12:00 |
01:43:39.82 |
-24:59:04.5 |
HIP 7993 |
25.46 |
| 2026-05-21 00:00 |
01:43:45.15 |
-24:59:05.1 |
HIP 8209 |
26.03 |
| 2026-05-21 12:00 |
01:43:50.45 |
-24:59:06.2 |
HIP 8209 |
24.84 |
| 2026-05-22 00:00 |
01:43:55.73 |
-24:59:07.7 |
HIP 8209 |
23.66 |
| 2026-05-22 12:00 |
01:44:00.99 |
-24:59:09.7 |
HIP 8209 |
22.48 |
| 2026-05-23 00:00 |
01:44:06.22 |
-24:59:12.2 |
HIP 8209 |
21.31 |
| 2026-05-23 12:00 |
01:44:11.42 |
-24:59:15.0 |
HIP 8209 |
20.14 |
| 2026-05-24 00:00 |
01:44:16.60 |
-24:59:18.3 |
HIP 8209 |
18.98 |
| 2026-05-24 12:00 |
01:44:21.75 |
-24:59:22.1 |
HIP 8209 |
17.83 |
| 2026-05-25 00:00 |
01:44:26.88 |
-24:59:26.3 |
HIP 8209 |
16.68 |
| 2026-05-25 12:00 |
01:44:31.98 |
-24:59:30.9 |
HIP 8209 |
15.53 |
| 2026-05-26 00:00 |
01:44:37.05 |
-24:59:36.0 |
HIP 8209 |
14.40 |
| 2026-05-26 12:00 |
01:44:42.10 |
-24:59:41.5 |
HIP 8209 |
13.27 |
| 2026-05-27 00:00 |
01:44:47.12 |
-24:59:47.5 |
HIP 8209 |
12.15 |
| 2026-05-27 12:00 |
01:44:52.11 |
-24:59:53.9 |
HIP 8209 |
11.03 |
| 2026-05-28 00:00 |
01:44:57.07 |
-25:00:00.8 |
HIP 8209 |
9.93 |
| 2026-05-28 12:00 |
01:45:02.00 |
-25:00:08.0 |
HIP 8209 |
8.83 |
| 2026-05-29 00:00 |
01:45:06.91 |
-25:00:15.7 |
HIP 8209 |
7.75 |
| 2026-05-29 12:00 |
01:45:11.79 |
-25:00:23.9 |
HIP 8209 |
6.68 |
| 2026-05-30 00:00 |
01:45:16.63 |
-25:00:32.5 |
HIP 8209 |
5.63 |
| 2026-05-30 12:00 |
01:45:21.45 |
-25:00:41.5 |
HIP 8209 |
4.60 |
| 2026-05-31 00:00 |
01:45:26.24 |
-25:00:51.0 |
HIP 8209 |
3.63 |
| 2026-05-31 12:00 |
01:45:31.00 |
-25:01:00.9 |
HIP 8209 |
2.75 |
| 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 |