| Parameter |
Value |
| Designation |
123P/West-Hartley |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2019-02-04T20:19:41.352960Z |
| Orbit solution date (soln_date, UTC) |
2026-04-27T16:15:41Z |
| Obs used |
3574 |
| NEO |
- |
| M1 |
8.200 |
| K1 |
18.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2017-01-12.0000000 |
| e |
0.44911917 |
| q (au) |
2.126475 |
| a (au) |
3.860136 |
| i (deg) |
15.358521 |
| Ω (om, deg) |
46.504182 |
| ω (w, deg) |
102.973946 |
| M (ma, deg) |
262.032181 |
Magnitude
Scatter + Global Linear
$$
M_a = (9.204 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
9.204 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.673 |
| k |
0.995 |
| 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
Finding Chart
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-05-12 00:00 |
05:48:03.84 |
+33:15:07.1 |
HIP 27252 |
24.69 |
| 2026-05-12 12:00 |
05:49:09.59 |
+33:15:38.7 |
HIP 27528 |
18.88 |
| 2026-05-13 00:00 |
05:50:15.49 |
+33:16:08.8 |
HIP 27528 |
18.79 |
| 2026-05-13 12:00 |
05:51:21.52 |
+33:16:37.3 |
HIP 27646 |
18.84 |
| 2026-05-14 00:00 |
05:52:27.70 |
+33:17:04.2 |
HIP 27806 |
10.58 |
| 2026-05-14 12:00 |
05:53:34.02 |
+33:17:29.5 |
HIP 27806 |
10.35 |
| 2026-05-15 00:00 |
05:54:40.47 |
+33:17:53.3 |
HIP 28101 |
21.56 |
| 2026-05-15 12:00 |
05:55:47.07 |
+33:18:15.5 |
HIP 28101 |
7.67 |
| 2026-05-16 00:00 |
05:56:53.79 |
+33:18:36.1 |
HIP 28101 |
6.37 |
| 2026-05-16 12:00 |
05:58:00.66 |
+33:18:55.0 |
HIP 28212 |
5.47 |
| 2026-05-17 00:00 |
05:59:07.65 |
+33:19:12.3 |
HIP 28429 |
17.77 |
| 2026-05-17 12:00 |
06:00:14.78 |
+33:19:28.0 |
HIP 28429 |
11.25 |
| 2026-05-18 00:00 |
06:01:22.03 |
+33:19:42.0 |
HIP 28429 |
18.21 |
| 2026-05-18 12:00 |
06:02:29.42 |
+33:19:54.4 |
HIP 28429 |
30.55 |
| 2026-05-19 00:00 |
06:03:36.93 |
+33:20:05.1 |
HIP 28861 |
29.10 |
| 2026-05-19 12:00 |
06:04:44.56 |
+33:20:14.2 |
HIP 28861 |
18.78 |
| 2026-05-20 00:00 |
06:05:52.32 |
+33:20:21.5 |
HIP 28861 |
16.05 |
| 2026-05-20 12:00 |
06:07:00.20 |
+33:20:27.2 |
HIP 28994 |
17.12 |
| 2026-05-21 00:00 |
06:08:08.20 |
+33:20:31.1 |
HIP 28994 |
21.64 |
| 2026-05-21 12:00 |
06:09:16.32 |
+33:20:33.4 |
HIP 29230 |
16.03 |
| 2026-05-22 00:00 |
06:10:24.56 |
+33:20:33.9 |
HIP 29230 |
16.72 |
| 2026-05-22 12:00 |
06:11:32.91 |
+33:20:32.6 |
HIP 29309 |
22.95 |
| 2026-05-23 00:00 |
06:12:41.38 |
+33:20:29.7 |
HIP 29534 |
13.46 |
| 2026-05-23 12:00 |
06:13:49.96 |
+33:20:24.9 |
HIP 29581 |
6.16 |
| 2026-05-24 00:00 |
06:14:58.66 |
+33:20:18.5 |
HIP 29581 |
13.40 |
| 2026-05-24 12:00 |
06:16:07.46 |
+33:20:10.2 |
HIP 29760 |
8.32 |
| 2026-05-25 00:00 |
06:17:16.37 |
+33:20:00.2 |
HIP 29760 |
17.57 |
| 2026-05-25 12:00 |
06:18:25.39 |
+33:19:48.4 |
HIP 29987 |
9.97 |
| 2026-05-26 00:00 |
06:19:34.51 |
+33:19:34.7 |
HIP 29987 |
13.86 |
| 2026-05-26 12:00 |
06:20:43.74 |
+33:19:19.3 |
HIP 29987 |
26.51 |
| 2026-05-27 00:00 |
06:21:53.08 |
+33:19:02.1 |
HIP 30367 |
26.33 |
| 2026-05-27 12:00 |
06:23:02.51 |
+33:18:43.0 |
HIP 30367 |
20.42 |
| 2026-05-28 00:00 |
06:24:12.05 |
+33:18:22.1 |
HIP 30573 |
17.45 |
| 2026-05-28 12:00 |
06:25:21.69 |
+33:17:59.4 |
HIP 30573 |
3.97 |
| 2026-05-29 00:00 |
06:26:31.43 |
+33:17:34.9 |
HIP 30573 |
12.30 |
| 2026-05-29 12:00 |
06:27:41.26 |
+33:17:08.4 |
HIP 30748 |
9.61 |
| 2026-05-30 00:00 |
06:28:51.19 |
+33:16:40.1 |
HIP 30748 |
17.41 |
| 2026-05-30 12:00 |
06:30:01.21 |
+33:16:10.0 |
HIP 31054 |
30.42 |
| 2026-05-31 00:00 |
06:31:11.33 |
+33:15:38.0 |
HIP 31054 |
27.41 |
| 2026-05-31 12:00 |
06:32:21.54 |
+33:15:04.1 |
HIP 31290 |
21.77 |
| 2026-06-01 00:00 |
06:33:31.85 |
+33:14:28.2 |
HIP 31290 |
13.22 |
| 2026-06-01 12:00 |
06:34:42.24 |
+33:13:50.5 |
HIP 31467 |
16.59 |
| 2026-06-02 00:00 |
06:35:52.72 |
+33:13:10.9 |
HIP 31585 |
13.68 |