| Parameter |
Value |
| Designation |
C/1978 A1 (West) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1977-07-21T10:46:21.555840Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:26Z |
| Obs used |
60 |
| NEO |
- |
| M1 |
6.000 |
| K1 |
8.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1978-03-26.0000000 |
| e |
1.00269511 |
| q (au) |
5.606239 |
| a (au) |
-2080.153011 |
| i (deg) |
116.921045 |
| Ω (om, deg) |
211.624226 |
| ω (w, deg) |
343.273891 |
| M (ma, deg) |
0.002572 |
Magnitude
Scatter + Global Linear
$$
M_a = (-0.758 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
-0.758 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.506 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-05-12 00:00 |
02:41:14.60 |
+60:30:23.4 |
HIP 12543 |
3.04 |
| 2026-05-12 12:00 |
02:41:17.74 |
+60:30:29.9 |
HIP 12543 |
2.81 |
| 2026-05-13 00:00 |
02:41:20.87 |
+60:30:36.5 |
HIP 12543 |
2.62 |
| 2026-05-13 12:00 |
02:41:24.00 |
+60:30:43.3 |
HIP 12543 |
2.47 |
| 2026-05-14 00:00 |
02:41:27.13 |
+60:30:50.2 |
HIP 12543 |
2.39 |
| 2026-05-14 12:00 |
02:41:30.25 |
+60:30:57.3 |
HIP 12543 |
2.37 |
| 2026-05-15 00:00 |
02:41:33.36 |
+60:31:04.4 |
HIP 12543 |
2.41 |
| 2026-05-15 12:00 |
02:41:36.47 |
+60:31:11.7 |
HIP 12543 |
2.51 |
| 2026-05-16 00:00 |
02:41:39.58 |
+60:31:19.2 |
HIP 12543 |
2.67 |
| 2026-05-16 12:00 |
02:41:42.68 |
+60:31:26.8 |
HIP 12543 |
2.88 |
| 2026-05-17 00:00 |
02:41:45.77 |
+60:31:34.5 |
HIP 12543 |
3.12 |
| 2026-05-17 12:00 |
02:41:48.86 |
+60:31:42.3 |
HIP 12543 |
3.39 |
| 2026-05-18 00:00 |
02:41:51.94 |
+60:31:50.3 |
HIP 12543 |
3.68 |
| 2026-05-18 12:00 |
02:41:55.02 |
+60:31:58.4 |
HIP 12543 |
3.99 |
| 2026-05-19 00:00 |
02:41:58.09 |
+60:32:06.6 |
HIP 12543 |
4.32 |
| 2026-05-19 12:00 |
02:42:01.15 |
+60:32:14.9 |
HIP 12543 |
4.65 |
| 2026-05-20 00:00 |
02:42:04.21 |
+60:32:23.4 |
HIP 12543 |
4.99 |
| 2026-05-20 12:00 |
02:42:07.26 |
+60:32:32.0 |
HIP 12543 |
5.34 |
| 2026-05-21 00:00 |
02:42:10.30 |
+60:32:40.7 |
HIP 12543 |
5.70 |
| 2026-05-21 12:00 |
02:42:13.33 |
+60:32:49.6 |
HIP 12543 |
6.06 |
| 2026-05-22 00:00 |
02:42:16.36 |
+60:32:58.6 |
HIP 12543 |
6.43 |
| 2026-05-22 12:00 |
02:42:19.37 |
+60:33:07.7 |
HIP 12543 |
6.79 |
| 2026-05-23 00:00 |
02:42:22.38 |
+60:33:16.9 |
HIP 12543 |
7.16 |
| 2026-05-23 12:00 |
02:42:25.38 |
+60:33:26.2 |
HIP 12543 |
7.53 |
| 2026-05-24 00:00 |
02:42:28.38 |
+60:33:35.7 |
HIP 12543 |
7.91 |
| 2026-05-24 12:00 |
02:42:31.36 |
+60:33:45.3 |
HIP 12543 |
8.28 |
| 2026-05-25 00:00 |
02:42:34.33 |
+60:33:55.0 |
HIP 12729 |
8.14 |
| 2026-05-25 12:00 |
02:42:37.30 |
+60:34:04.8 |
HIP 12729 |
7.75 |
| 2026-05-26 00:00 |
02:42:40.26 |
+60:34:14.8 |
HIP 12729 |
7.35 |
| 2026-05-26 12:00 |
02:42:43.20 |
+60:34:24.8 |
HIP 12729 |
6.95 |
| 2026-05-27 00:00 |
02:42:46.14 |
+60:34:35.0 |
HIP 12729 |
6.56 |
| 2026-05-27 12:00 |
02:42:49.07 |
+60:34:45.3 |
HIP 12729 |
6.16 |
| 2026-05-28 00:00 |
02:42:51.98 |
+60:34:55.7 |
HIP 12729 |
5.77 |
| 2026-05-28 12:00 |
02:42:54.89 |
+60:35:06.2 |
HIP 12729 |
5.38 |
| 2026-05-29 00:00 |
02:42:57.79 |
+60:35:16.8 |
HIP 12729 |
4.99 |
| 2026-05-29 12:00 |
02:43:00.67 |
+60:35:27.5 |
HIP 12729 |
4.61 |
| 2026-05-30 00:00 |
02:43:03.55 |
+60:35:38.4 |
HIP 12729 |
4.22 |
| 2026-05-30 12:00 |
02:43:06.41 |
+60:35:49.3 |
HIP 12729 |
3.84 |
| 2026-05-31 00:00 |
02:43:09.26 |
+60:36:00.4 |
HIP 12729 |
3.47 |
| 2026-05-31 12:00 |
02:43:12.10 |
+60:36:11.6 |
HIP 12729 |
3.10 |
| 2026-06-01 00:00 |
02:43:14.93 |
+60:36:22.9 |
HIP 12729 |
2.74 |
| 2026-06-01 12:00 |
02:43:17.75 |
+60:36:34.3 |
HIP 12729 |
2.39 |
| 2026-06-02 00:00 |
02:43:20.56 |
+60:36:45.8 |
HIP 12729 |
2.06 |