| Parameter |
Value |
| Designation |
C/1978 H1 (Meier) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1978-11-11T09:49:21.498240Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:26Z |
| Obs used |
276 |
| NEO |
- |
| M1 |
5.100 |
| K1 |
7.250 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1978-12-13.0000000 |
| e |
1.00084968 |
| q (au) |
1.136526 |
| a (au) |
-1337.595649 |
| i (deg) |
43.761381 |
| Ω (om, deg) |
349.344795 |
| ω (w, deg) |
231.402033 |
| M (ma, deg) |
0.000636 |
Magnitude
Scatter + Global Linear
$$
M_a = (1.696 + 4.508\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
1.696 |
| n |
4.508 |
| gf |
1.000 |
| gb |
-0.500 |
| 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
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) |
End (UTC) |
a |
b |
| 1978-04-27 |
1978-11-09 |
-2.4267 |
+0.754 |
| 1978-11-13 |
1979-12-21 |
-2.6793 |
+1.685 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-07-29 00:00 |
00:26:56.36 |
+29:51:08.0 |
HIP 2102 |
21.14 |
| 2026-07-29 12:00 |
00:26:55.57 |
+29:51:13.9 |
HIP 2102 |
21.02 |
| 2026-07-30 00:00 |
00:26:54.75 |
+29:51:19.6 |
HIP 2102 |
20.90 |
| 2026-07-30 12:00 |
00:26:53.93 |
+29:51:25.2 |
HIP 2102 |
20.78 |
| 2026-07-31 00:00 |
00:26:53.09 |
+29:51:30.8 |
HIP 2102 |
20.66 |
| 2026-07-31 12:00 |
00:26:52.24 |
+29:51:36.2 |
HIP 2102 |
20.55 |
| 2026-08-01 00:00 |
00:26:51.38 |
+29:51:41.5 |
HIP 2102 |
20.44 |
| 2026-08-01 12:00 |
00:26:50.51 |
+29:51:46.7 |
HIP 2102 |
20.33 |
| 2026-08-02 00:00 |
00:26:49.62 |
+29:51:51.8 |
HIP 2102 |
20.23 |
| 2026-08-02 12:00 |
00:26:48.72 |
+29:51:56.8 |
HIP 2102 |
20.13 |
| 2026-08-03 00:00 |
00:26:47.81 |
+29:52:01.6 |
HIP 2102 |
20.03 |
| 2026-08-03 12:00 |
00:26:46.89 |
+29:52:06.4 |
HIP 2102 |
19.93 |
| 2026-08-04 00:00 |
00:26:45.95 |
+29:52:11.1 |
HIP 2102 |
19.84 |
| 2026-08-04 12:00 |
00:26:45.00 |
+29:52:15.6 |
HIP 2102 |
19.76 |
| 2026-08-05 00:00 |
00:26:44.04 |
+29:52:20.1 |
HIP 2102 |
19.67 |
| 2026-08-05 12:00 |
00:26:43.07 |
+29:52:24.4 |
HIP 2102 |
19.59 |
| 2026-08-06 00:00 |
00:26:42.09 |
+29:52:28.6 |
HIP 2102 |
19.52 |
| 2026-08-06 12:00 |
00:26:41.09 |
+29:52:32.7 |
HIP 2102 |
19.45 |
| 2026-08-07 00:00 |
00:26:40.09 |
+29:52:36.7 |
HIP 2102 |
19.38 |
| 2026-08-07 12:00 |
00:26:39.07 |
+29:52:40.6 |
HIP 2102 |
19.32 |
| 2026-08-08 00:00 |
00:26:38.04 |
+29:52:44.4 |
HIP 2102 |
19.26 |
| 2026-08-08 12:00 |
00:26:37.00 |
+29:52:48.0 |
HIP 2102 |
19.20 |
| 2026-08-09 00:00 |
00:26:35.94 |
+29:52:51.6 |
HIP 2102 |
19.15 |
| 2026-08-09 12:00 |
00:26:34.88 |
+29:52:55.0 |
HIP 2102 |
19.11 |
| 2026-08-10 00:00 |
00:26:33.80 |
+29:52:58.3 |
HIP 2102 |
19.07 |
| 2026-08-10 12:00 |
00:26:32.72 |
+29:53:01.5 |
HIP 2102 |
19.04 |
| 2026-08-11 00:00 |
00:26:31.62 |
+29:53:04.6 |
HIP 1980 |
18.96 |
| 2026-08-11 12:00 |
00:26:30.51 |
+29:53:07.6 |
HIP 1980 |
18.73 |
| 2026-08-12 00:00 |
00:26:29.39 |
+29:53:10.4 |
HIP 1980 |
18.49 |
| 2026-08-12 12:00 |
00:26:28.25 |
+29:53:13.1 |
HIP 1980 |
18.26 |
| 2026-08-13 00:00 |
00:26:27.11 |
+29:53:15.8 |
HIP 1980 |
18.02 |
| 2026-08-13 12:00 |
00:26:25.96 |
+29:53:18.3 |
HIP 1980 |
17.77 |
| 2026-08-14 00:00 |
00:26:24.79 |
+29:53:20.6 |
HIP 1980 |
17.53 |
| 2026-08-14 12:00 |
00:26:23.62 |
+29:53:22.9 |
HIP 1980 |
17.28 |
| 2026-08-15 00:00 |
00:26:22.43 |
+29:53:25.1 |
HIP 1980 |
17.03 |
| 2026-08-15 12:00 |
00:26:21.24 |
+29:53:27.1 |
HIP 1980 |
16.78 |
| 2026-08-16 00:00 |
00:26:20.03 |
+29:53:29.0 |
HIP 1980 |
16.53 |
| 2026-08-16 12:00 |
00:26:18.81 |
+29:53:30.8 |
HIP 1980 |
16.28 |
| 2026-08-17 00:00 |
00:26:17.59 |
+29:53:32.5 |
HIP 1980 |
16.02 |
| 2026-08-17 12:00 |
00:26:16.35 |
+29:53:34.1 |
HIP 1980 |
15.76 |
| 2026-08-18 00:00 |
00:26:15.10 |
+29:53:35.5 |
HIP 1980 |
15.50 |
| 2026-08-18 12:00 |
00:26:13.85 |
+29:53:36.9 |
HIP 1980 |
15.23 |
| 2026-08-19 00:00 |
00:26:12.58 |
+29:53:38.1 |
HIP 1980 |
14.97 |