| 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) |
| 2026-07-29 00:00 |
01:50:18.36 |
-26:04:10.4 |
HIP 8444 |
20.04 |
| 2026-07-29 12:00 |
01:50:18.11 |
-26:05:00.0 |
HIP 8444 |
19.80 |
| 2026-07-30 00:00 |
01:50:17.81 |
-26:05:49.8 |
HIP 8444 |
19.58 |
| 2026-07-30 12:00 |
01:50:17.47 |
-26:06:39.7 |
HIP 8444 |
19.38 |
| 2026-07-31 00:00 |
01:50:17.07 |
-26:07:29.8 |
HIP 8444 |
19.21 |
| 2026-07-31 12:00 |
01:50:16.62 |
-26:08:20.0 |
HIP 8444 |
19.06 |
| 2026-08-01 00:00 |
01:50:16.13 |
-26:09:10.4 |
HIP 8444 |
18.93 |
| 2026-08-01 12:00 |
01:50:15.58 |
-26:10:01.0 |
HIP 8444 |
18.83 |
| 2026-08-02 00:00 |
01:50:14.99 |
-26:10:51.7 |
HIP 8444 |
18.76 |
| 2026-08-02 12:00 |
01:50:14.34 |
-26:11:42.5 |
HIP 8444 |
18.71 |
| 2026-08-03 00:00 |
01:50:13.65 |
-26:12:33.5 |
HIP 8444 |
18.70 |
| 2026-08-03 12:00 |
01:50:12.91 |
-26:13:24.6 |
HIP 8444 |
18.71 |
| 2026-08-04 00:00 |
01:50:12.12 |
-26:14:15.9 |
HIP 8444 |
18.76 |
| 2026-08-04 12:00 |
01:50:11.28 |
-26:15:07.2 |
HIP 8444 |
18.83 |
| 2026-08-05 00:00 |
01:50:10.39 |
-26:15:58.7 |
HIP 8444 |
18.94 |
| 2026-08-05 12:00 |
01:50:09.45 |
-26:16:50.4 |
HIP 8444 |
19.08 |
| 2026-08-06 00:00 |
01:50:08.46 |
-26:17:42.1 |
HIP 8444 |
19.25 |
| 2026-08-06 12:00 |
01:50:07.42 |
-26:18:33.9 |
HIP 8444 |
19.44 |
| 2026-08-07 00:00 |
01:50:06.33 |
-26:19:25.9 |
HIP 8444 |
19.67 |
| 2026-08-07 12:00 |
01:50:05.19 |
-26:20:18.0 |
HIP 8444 |
19.93 |
| 2026-08-08 00:00 |
01:50:04.01 |
-26:21:10.1 |
HIP 8444 |
20.22 |
| 2026-08-08 12:00 |
01:50:02.77 |
-26:22:02.4 |
HIP 8444 |
20.54 |
| 2026-08-09 00:00 |
01:50:01.49 |
-26:22:54.7 |
HIP 8417 |
20.65 |
| 2026-08-09 12:00 |
01:50:00.15 |
-26:23:47.2 |
HIP 8417 |
20.72 |
| 2026-08-10 00:00 |
01:49:58.77 |
-26:24:39.7 |
HIP 8435 |
20.33 |
| 2026-08-10 12:00 |
01:49:57.34 |
-26:25:32.3 |
HIP 8435 |
19.57 |
| 2026-08-11 00:00 |
01:49:55.86 |
-26:26:25.0 |
HIP 8435 |
18.83 |
| 2026-08-11 12:00 |
01:49:54.33 |
-26:27:17.7 |
HIP 8435 |
18.08 |
| 2026-08-12 00:00 |
01:49:52.75 |
-26:28:10.5 |
HIP 8435 |
17.35 |
| 2026-08-12 12:00 |
01:49:51.12 |
-26:29:03.4 |
HIP 8435 |
16.63 |
| 2026-08-13 00:00 |
01:49:49.45 |
-26:29:56.3 |
HIP 8435 |
15.93 |
| 2026-08-13 12:00 |
01:49:47.72 |
-26:30:49.2 |
HIP 8435 |
15.24 |
| 2026-08-14 00:00 |
01:49:45.95 |
-26:31:42.2 |
HIP 8435 |
14.57 |
| 2026-08-14 12:00 |
01:49:44.13 |
-26:32:35.3 |
HIP 8435 |
13.93 |
| 2026-08-15 00:00 |
01:49:42.26 |
-26:33:28.4 |
HIP 8435 |
13.31 |
| 2026-08-15 12:00 |
01:49:40.35 |
-26:34:21.5 |
HIP 8435 |
12.74 |
| 2026-08-16 00:00 |
01:49:38.38 |
-26:35:14.6 |
HIP 8435 |
12.20 |
| 2026-08-16 12:00 |
01:49:36.37 |
-26:36:07.8 |
HIP 8435 |
11.71 |
| 2026-08-17 00:00 |
01:49:34.31 |
-26:37:00.9 |
HIP 8435 |
11.28 |
| 2026-08-17 12:00 |
01:49:32.20 |
-26:37:54.1 |
HIP 8435 |
10.91 |
| 2026-08-18 00:00 |
01:49:30.05 |
-26:38:47.3 |
HIP 8435 |
10.62 |
| 2026-08-18 12:00 |
01:49:27.85 |
-26:39:40.5 |
HIP 8435 |
10.40 |
| 2026-08-19 00:00 |
01:49:25.60 |
-26:40:33.7 |
HIP 8435 |
10.27 |