| 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 |
-0.507 |
| 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) |
| 2026-07-29 00:00 |
02:46:40.42 |
+61:06:06.4 |
HIP 12817 |
25.92 |
| 2026-07-29 12:00 |
02:46:40.82 |
+61:06:23.3 |
HIP 12817 |
25.71 |
| 2026-07-30 00:00 |
02:46:41.20 |
+61:06:40.2 |
HIP 12817 |
25.50 |
| 2026-07-30 12:00 |
02:46:41.55 |
+61:06:57.1 |
HIP 12817 |
25.29 |
| 2026-07-31 00:00 |
02:46:41.87 |
+61:07:13.9 |
HIP 12817 |
25.08 |
| 2026-07-31 12:00 |
02:46:42.16 |
+61:07:30.7 |
HIP 12817 |
24.87 |
| 2026-08-01 00:00 |
02:46:42.43 |
+61:07:47.5 |
HIP 12817 |
24.66 |
| 2026-08-01 12:00 |
02:46:42.66 |
+61:08:04.3 |
HIP 12817 |
24.45 |
| 2026-08-02 00:00 |
02:46:42.88 |
+61:08:21.0 |
HIP 12817 |
24.24 |
| 2026-08-02 12:00 |
02:46:43.06 |
+61:08:37.8 |
HIP 12817 |
24.03 |
| 2026-08-03 00:00 |
02:46:43.22 |
+61:08:54.4 |
HIP 12817 |
23.81 |
| 2026-08-03 12:00 |
02:46:43.34 |
+61:09:11.1 |
HIP 12817 |
23.60 |
| 2026-08-04 00:00 |
02:46:43.45 |
+61:09:27.7 |
HIP 12817 |
23.39 |
| 2026-08-04 12:00 |
02:46:43.52 |
+61:09:44.3 |
HIP 12817 |
23.18 |
| 2026-08-05 00:00 |
02:46:43.57 |
+61:10:00.9 |
HIP 12817 |
22.97 |
| 2026-08-05 12:00 |
02:46:43.58 |
+61:10:17.4 |
HIP 12817 |
22.75 |
| 2026-08-06 00:00 |
02:46:43.57 |
+61:10:33.8 |
HIP 12817 |
22.54 |
| 2026-08-06 12:00 |
02:46:43.54 |
+61:10:50.3 |
HIP 12817 |
22.33 |
| 2026-08-07 00:00 |
02:46:43.47 |
+61:11:06.7 |
HIP 12817 |
22.11 |
| 2026-08-07 12:00 |
02:46:43.38 |
+61:11:23.0 |
HIP 12817 |
21.90 |
| 2026-08-08 00:00 |
02:46:43.26 |
+61:11:39.4 |
HIP 12817 |
21.69 |
| 2026-08-08 12:00 |
02:46:43.11 |
+61:11:55.6 |
HIP 12817 |
21.47 |
| 2026-08-09 00:00 |
02:46:42.93 |
+61:12:11.9 |
HIP 12817 |
21.26 |
| 2026-08-09 12:00 |
02:46:42.73 |
+61:12:28.0 |
HIP 12817 |
21.04 |
| 2026-08-10 00:00 |
02:46:42.50 |
+61:12:44.2 |
HIP 12817 |
20.82 |
| 2026-08-10 12:00 |
02:46:42.24 |
+61:13:00.2 |
HIP 12817 |
20.61 |
| 2026-08-11 00:00 |
02:46:41.95 |
+61:13:16.3 |
HIP 12817 |
20.39 |
| 2026-08-11 12:00 |
02:46:41.63 |
+61:13:32.3 |
HIP 12817 |
20.17 |
| 2026-08-12 00:00 |
02:46:41.28 |
+61:13:48.2 |
HIP 12817 |
19.95 |
| 2026-08-12 12:00 |
02:46:40.91 |
+61:14:04.1 |
HIP 12817 |
19.74 |
| 2026-08-13 00:00 |
02:46:40.51 |
+61:14:19.9 |
HIP 12817 |
19.52 |
| 2026-08-13 12:00 |
02:46:40.08 |
+61:14:35.6 |
HIP 12817 |
19.30 |
| 2026-08-14 00:00 |
02:46:39.62 |
+61:14:51.3 |
HIP 12817 |
19.08 |
| 2026-08-14 12:00 |
02:46:39.14 |
+61:15:07.0 |
HIP 12817 |
18.86 |
| 2026-08-15 00:00 |
02:46:38.62 |
+61:15:22.5 |
HIP 12817 |
18.64 |
| 2026-08-15 12:00 |
02:46:38.08 |
+61:15:38.1 |
HIP 12817 |
18.41 |
| 2026-08-16 00:00 |
02:46:37.51 |
+61:15:53.5 |
HIP 12817 |
18.19 |
| 2026-08-16 12:00 |
02:46:36.91 |
+61:16:08.9 |
HIP 12817 |
17.97 |
| 2026-08-17 00:00 |
02:46:36.29 |
+61:16:24.2 |
HIP 12817 |
17.75 |
| 2026-08-17 12:00 |
02:46:35.63 |
+61:16:39.5 |
HIP 12817 |
17.52 |
| 2026-08-18 00:00 |
02:46:34.95 |
+61:16:54.6 |
HIP 12817 |
17.30 |
| 2026-08-18 12:00 |
02:46:34.24 |
+61:17:09.7 |
HIP 12817 |
17.07 |
| 2026-08-19 00:00 |
02:46:33.50 |
+61:17:24.8 |
HIP 12817 |
16.84 |