| Parameter |
Value |
| Designation |
123P/West-Hartley |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2019-02-04T20:32:10.648320Z |
| Orbit solution date (soln_date, UTC) |
2026-07-07T05:59:09Z |
| Obs used |
3587 |
| NEO |
- |
| M1 |
8.200 |
| K1 |
18.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2017-01-25.0000000 |
| e |
0.44911568 |
| q (au) |
2.126469 |
| a (au) |
3.860102 |
| i (deg) |
15.358650 |
| Ω (om, deg) |
46.503806 |
| ω (w, deg) |
102.975490 |
| M (ma, deg) |
263.719220 |
Magnitude
Scatter + Global Linear
$$
M_a = (9.015 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
9.015 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.747 |
| k |
0.999 |
| 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) |
| 2026-07-29 00:00 |
08:54:02.39 |
+28:16:56.1 |
HIP 43587 |
19.21 |
| 2026-07-29 12:00 |
08:55:14.66 |
+28:12:26.2 |
HIP 43834 |
17.67 |
| 2026-07-30 00:00 |
08:56:26.87 |
+28:07:54.4 |
HIP 43834 |
16.08 |
| 2026-07-30 12:00 |
08:57:39.04 |
+28:03:20.9 |
HIP 43834 |
27.45 |
| 2026-07-31 00:00 |
08:58:51.17 |
+27:58:45.6 |
HIP 44342 |
39.52 |
| 2026-07-31 12:00 |
09:00:03.24 |
+27:54:08.5 |
HIP 44342 |
23.34 |
| 2026-08-01 00:00 |
09:01:15.27 |
+27:49:29.7 |
HIP 44342 |
8.78 |
| 2026-08-01 12:00 |
09:02:27.25 |
+27:44:49.1 |
HIP 44342 |
12.62 |
| 2026-08-02 00:00 |
09:03:39.18 |
+27:40:06.7 |
HIP 44512 |
15.37 |
| 2026-08-02 12:00 |
09:04:51.05 |
+27:35:22.6 |
HIP 44512 |
20.64 |
| 2026-08-03 00:00 |
09:06:02.88 |
+27:30:36.8 |
HIP 44823 |
26.75 |
| 2026-08-03 12:00 |
09:07:14.66 |
+27:25:49.2 |
HIP 44823 |
13.18 |
| 2026-08-04 00:00 |
09:08:26.39 |
+27:21:00.0 |
HIP 44920 |
9.59 |
| 2026-08-04 12:00 |
09:09:38.06 |
+27:16:08.9 |
HIP 44920 |
12.44 |
| 2026-08-05 00:00 |
09:10:49.68 |
+27:11:16.2 |
HIP 44920 |
27.79 |
| 2026-08-05 12:00 |
09:12:01.25 |
+27:06:21.8 |
HIP 45178 |
14.50 |
| 2026-08-06 00:00 |
09:13:12.76 |
+27:01:25.7 |
HIP 45178 |
13.99 |
| 2026-08-06 12:00 |
09:14:24.22 |
+26:56:28.0 |
HIP 45178 |
27.15 |
| 2026-08-07 00:00 |
09:15:35.63 |
+26:51:28.6 |
HIP 45490 |
24.57 |
| 2026-08-07 12:00 |
09:16:46.98 |
+26:46:27.5 |
HIP 45490 |
20.26 |
| 2026-08-08 00:00 |
09:17:58.27 |
+26:41:24.8 |
HIP 45490 |
27.84 |
| 2026-08-08 12:00 |
09:19:09.51 |
+26:36:20.5 |
HIP 45723 |
21.27 |
| 2026-08-09 00:00 |
09:20:20.69 |
+26:31:14.5 |
HIP 45723 |
21.77 |
| 2026-08-09 12:00 |
09:21:31.81 |
+26:26:06.9 |
HIP 45914 |
24.81 |
| 2026-08-10 00:00 |
09:22:42.88 |
+26:20:57.8 |
HIP 46146 |
27.95 |
| 2026-08-10 12:00 |
09:23:53.88 |
+26:15:47.0 |
HIP 46146 |
11.27 |
| 2026-08-11 00:00 |
09:25:04.83 |
+26:10:34.7 |
HIP 46146 |
5.74 |
| 2026-08-11 12:00 |
09:26:15.71 |
+26:05:20.8 |
HIP 46255 |
9.30 |
| 2026-08-12 00:00 |
09:27:26.53 |
+26:00:05.4 |
HIP 46325 |
23.12 |
| 2026-08-12 12:00 |
09:28:37.29 |
+25:54:48.4 |
HIP 46490 |
18.45 |
| 2026-08-13 00:00 |
09:29:47.99 |
+25:49:29.9 |
HIP 46702 |
21.86 |
| 2026-08-13 12:00 |
09:30:58.62 |
+25:44:09.9 |
HIP 46702 |
15.92 |
| 2026-08-14 00:00 |
09:32:09.19 |
+25:38:48.4 |
HIP 46702 |
24.32 |
| 2026-08-14 12:00 |
09:33:19.70 |
+25:33:25.4 |
HIP 46702 |
38.63 |
| 2026-08-15 00:00 |
09:34:30.14 |
+25:28:00.9 |
HIP 47026 |
34.52 |
| 2026-08-15 12:00 |
09:35:40.51 |
+25:22:34.9 |
HIP 47026 |
29.64 |
| 2026-08-16 00:00 |
09:36:50.82 |
+25:17:07.5 |
HIP 47298 |
21.02 |
| 2026-08-16 12:00 |
09:38:01.06 |
+25:11:38.6 |
HIP 47298 |
11.32 |
| 2026-08-17 00:00 |
09:39:11.23 |
+25:06:08.4 |
HIP 47382 |
15.91 |
| 2026-08-17 12:00 |
09:40:21.33 |
+25:00:36.6 |
HIP 47382 |
26.45 |
| 2026-08-18 00:00 |
09:41:31.37 |
+24:55:03.5 |
HIP 47685 |
31.50 |
| 2026-08-18 12:00 |
09:42:41.33 |
+24:49:29.0 |
HIP 47685 |
16.21 |
| 2026-08-19 00:00 |
09:43:51.23 |
+24:43:53.1 |
HIP 47685 |
9.96 |