| Parameter |
Value |
| Designation |
C/2023 H2 (Lemmon) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2023-10-29T04:33:37.779840Z |
| Orbit solution date (soln_date, UTC) |
2024-07-30T14:57:25Z |
| Obs used |
724 |
| NEO |
- |
| M1 |
16.100 |
| K1 |
5.500 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2023-04-23T06:42:47.548800Z |
| Discovery magnitude (MPC) |
20.78 G |
| Discovery observatory (MPC) |
G96 · Mt. Lemmon Survey |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2023-10-07.0000000 |
| e |
0.99628184 |
| q (au) |
0.894405 |
| a (au) |
240.550492 |
| i (deg) |
113.753483 |
| Ω (om, deg) |
217.044806 |
| ω (w, deg) |
150.650349 |
| M (ma, deg) |
359.994138 |
Magnitude
Scatter + Global Linear
$$
M_a = (13.783 + 4.803\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
13.783 |
| n |
4.803 |
| gf |
0.800 |
| gb |
-0.500 |
| k |
0.800 |
| δ90 |
1.000 |
| 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 |
| 2023-03-26 |
2023-10-28 |
+3.5183 |
-1.258 |
| 2023-10-29 |
2024-02-05 |
-12.4077 |
-0.879 |
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 |
16:01:03.96 |
-83:02:57.5 |
HIP 77248 |
26.91 |
| 2026-05-12 12:00 |
15:59:14.58 |
-83:02:42.9 |
HIP 77248 |
23.59 |
| 2026-05-13 00:00 |
15:57:25.21 |
-83:02:25.4 |
HIP 77248 |
20.27 |
| 2026-05-13 12:00 |
15:55:35.88 |
-83:02:04.8 |
HIP 77248 |
16.94 |
| 2026-05-14 00:00 |
15:53:46.64 |
-83:01:41.2 |
HIP 77248 |
13.60 |
| 2026-05-14 12:00 |
15:51:57.53 |
-83:01:14.6 |
HIP 77248 |
10.26 |
| 2026-05-15 00:00 |
15:50:08.59 |
-83:00:45.0 |
HIP 77248 |
6.91 |
| 2026-05-15 12:00 |
15:48:19.86 |
-83:00:12.3 |
HIP 77248 |
3.56 |
| 2026-05-16 00:00 |
15:46:31.39 |
-82:59:36.6 |
HIP 77248 |
0.27 |
| 2026-05-16 12:00 |
15:44:43.20 |
-82:58:57.9 |
HIP 77248 |
3.17 |
| 2026-05-17 00:00 |
15:42:55.35 |
-82:58:16.2 |
HIP 77248 |
6.54 |
| 2026-05-17 12:00 |
15:41:07.87 |
-82:57:31.5 |
HIP 77248 |
9.92 |
| 2026-05-18 00:00 |
15:39:20.80 |
-82:56:43.9 |
HIP 77248 |
13.29 |
| 2026-05-18 12:00 |
15:37:34.18 |
-82:55:53.2 |
HIP 77248 |
16.68 |
| 2026-05-19 00:00 |
15:35:48.04 |
-82:54:59.7 |
HIP 76642 |
19.86 |
| 2026-05-19 12:00 |
15:34:02.43 |
-82:54:03.1 |
HIP 76642 |
21.89 |
| 2026-05-20 00:00 |
15:32:17.37 |
-82:53:03.7 |
HIP 76966 |
24.12 |
| 2026-05-20 12:00 |
15:30:32.90 |
-82:52:01.4 |
HIP 76966 |
26.45 |
| 2026-05-21 00:00 |
15:28:49.06 |
-82:50:56.1 |
HIP 76966 |
28.98 |
| 2026-05-21 12:00 |
15:27:05.87 |
-82:49:48.1 |
HIP 76966 |
31.66 |
| 2026-05-22 00:00 |
15:25:23.38 |
-82:48:37.1 |
HIP 76966 |
34.46 |
| 2026-05-22 12:00 |
15:23:41.60 |
-82:47:23.4 |
HIP 76966 |
37.36 |
| 2026-05-23 00:00 |
15:22:00.57 |
-82:46:06.9 |
HIP 73771 |
35.78 |
| 2026-05-23 12:00 |
15:20:20.32 |
-82:44:47.6 |
HIP 73771 |
33.75 |
| 2026-05-24 00:00 |
15:18:40.87 |
-82:43:25.6 |
HIP 73771 |
31.98 |
| 2026-05-24 12:00 |
15:17:02.25 |
-82:42:00.9 |
HIP 73771 |
30.52 |
| 2026-05-25 00:00 |
15:15:24.48 |
-82:40:33.6 |
HIP 73771 |
29.41 |
| 2026-05-25 12:00 |
15:13:47.60 |
-82:39:03.5 |
HIP 73771 |
28.69 |
| 2026-05-26 00:00 |
15:12:11.61 |
-82:37:30.9 |
HIP 73771 |
28.40 |
| 2026-05-26 12:00 |
15:10:36.54 |
-82:35:55.6 |
HIP 73771 |
28.54 |
| 2026-05-27 00:00 |
15:09:02.41 |
-82:34:17.8 |
HIP 73771 |
29.12 |
| 2026-05-27 12:00 |
15:07:29.25 |
-82:32:37.5 |
HIP 72825 |
28.89 |
| 2026-05-28 00:00 |
15:05:57.06 |
-82:30:54.7 |
HIP 72825 |
26.71 |
| 2026-05-28 12:00 |
15:04:25.87 |
-82:29:09.4 |
HIP 72825 |
24.83 |
| 2026-05-29 00:00 |
15:02:55.69 |
-82:27:21.7 |
HIP 72825 |
23.34 |
| 2026-05-29 12:00 |
15:01:26.54 |
-82:25:31.6 |
HIP 72825 |
22.32 |
| 2026-05-30 00:00 |
14:59:58.42 |
-82:23:39.1 |
HIP 72825 |
21.82 |
| 2026-05-30 12:00 |
14:58:31.36 |
-82:21:44.3 |
HIP 72825 |
21.89 |
| 2026-05-31 00:00 |
14:57:05.36 |
-82:19:47.2 |
HIP 72825 |
22.52 |
| 2026-05-31 12:00 |
14:55:40.43 |
-82:17:47.9 |
HIP 72825 |
23.68 |
| 2026-06-01 00:00 |
14:54:16.59 |
-82:15:46.3 |
HIP 72081 |
23.08 |
| 2026-06-01 12:00 |
14:52:53.84 |
-82:13:42.5 |
HIP 72081 |
19.63 |
| 2026-06-02 00:00 |
14:51:32.19 |
-82:11:36.6 |
HIP 72081 |
16.18 |