C/1978 H1 (Meier)
| 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) |
| 2026-02-03 00:00 |
00:21:19.15 |
+28:57:43.7 |
HIP 1690 |
3.85 |
| 2026-02-03 12:00 |
00:21:20.23 |
+28:57:40.8 |
HIP 1690 |
3.91 |
| 2026-02-04 00:00 |
00:21:21.31 |
+28:57:38.0 |
HIP 1690 |
3.99 |
| 2026-02-04 12:00 |
00:21:22.40 |
+28:57:35.3 |
HIP 1690 |
4.09 |
| 2026-02-05 00:00 |
00:21:23.51 |
+28:57:32.8 |
HIP 1690 |
4.20 |
| 2026-02-05 12:00 |
00:21:24.62 |
+28:57:30.3 |
HIP 1690 |
4.32 |
| 2026-02-06 00:00 |
00:21:25.75 |
+28:57:28.0 |
HIP 1690 |
4.46 |
| 2026-02-06 12:00 |
00:21:26.89 |
+28:57:25.8 |
HIP 1690 |
4.61 |
| 2026-02-07 00:00 |
00:21:28.04 |
+28:57:23.8 |
HIP 1690 |
4.78 |
| 2026-02-07 12:00 |
00:21:29.20 |
+28:57:21.8 |
HIP 1690 |
4.95 |
| 2026-02-08 00:00 |
00:21:30.37 |
+28:57:20.0 |
HIP 1690 |
5.13 |
| 2026-02-08 12:00 |
00:21:31.55 |
+28:57:18.3 |
HIP 1690 |
5.33 |
| 2026-02-09 00:00 |
00:21:32.74 |
+28:57:16.7 |
HIP 1690 |
5.53 |
| 2026-02-09 12:00 |
00:21:33.95 |
+28:57:15.2 |
HIP 1690 |
5.74 |
| 2026-02-10 00:00 |
00:21:35.16 |
+28:57:13.9 |
HIP 1690 |
5.95 |
| 2026-02-10 12:00 |
00:21:36.38 |
+28:57:12.6 |
HIP 1690 |
6.18 |
| 2026-02-11 00:00 |
00:21:37.62 |
+28:57:11.5 |
HIP 1690 |
6.41 |
| 2026-02-11 12:00 |
00:21:38.86 |
+28:57:10.5 |
HIP 1690 |
6.64 |
| 2026-02-12 00:00 |
00:21:40.11 |
+28:57:09.7 |
HIP 1690 |
6.88 |
| 2026-02-12 12:00 |
00:21:41.38 |
+28:57:08.9 |
HIP 1690 |
7.13 |
| 2026-02-13 00:00 |
00:21:42.65 |
+28:57:08.3 |
HIP 1690 |
7.38 |
| 2026-02-13 12:00 |
00:21:43.94 |
+28:57:07.8 |
HIP 1690 |
7.64 |
| 2026-02-14 00:00 |
00:21:45.23 |
+28:57:07.4 |
HIP 1690 |
7.90 |
| 2026-02-14 12:00 |
00:21:46.53 |
+28:57:07.2 |
HIP 1690 |
8.16 |
| 2026-02-15 00:00 |
00:21:47.84 |
+28:57:07.0 |
HIP 1690 |
8.43 |
| 2026-02-15 12:00 |
00:21:49.17 |
+28:57:07.0 |
HIP 1690 |
8.70 |
| 2026-02-16 00:00 |
00:21:50.50 |
+28:57:07.1 |
HIP 1690 |
8.98 |
| 2026-02-16 12:00 |
00:21:51.84 |
+28:57:07.3 |
HIP 1690 |
9.26 |
| 2026-02-17 00:00 |
00:21:53.19 |
+28:57:07.7 |
HIP 1690 |
9.54 |
| 2026-02-17 12:00 |
00:21:54.54 |
+28:57:08.1 |
HIP 1690 |
9.83 |
| 2026-02-18 00:00 |
00:21:55.91 |
+28:57:08.7 |
HIP 1690 |
10.12 |
| 2026-02-18 12:00 |
00:21:57.29 |
+28:57:09.4 |
HIP 1690 |
10.41 |
| 2026-02-19 00:00 |
00:21:58.67 |
+28:57:10.3 |
HIP 1690 |
10.70 |
| 2026-02-19 12:00 |
00:22:00.06 |
+28:57:11.2 |
HIP 1690 |
11.00 |
| 2026-02-20 00:00 |
00:22:01.46 |
+28:57:12.3 |
HIP 1690 |
11.30 |
| 2026-02-20 12:00 |
00:22:02.87 |
+28:57:13.5 |
HIP 1690 |
11.61 |
| 2026-02-21 00:00 |
00:22:04.29 |
+28:57:14.8 |
HIP 1690 |
11.91 |
| 2026-02-21 12:00 |
00:22:05.72 |
+28:57:16.2 |
HIP 1690 |
12.22 |
| 2026-02-22 00:00 |
00:22:07.15 |
+28:57:17.8 |
HIP 1690 |
12.53 |
| 2026-02-22 12:00 |
00:22:08.59 |
+28:57:19.4 |
HIP 1690 |
12.84 |
| 2026-02-23 00:00 |
00:22:10.04 |
+28:57:21.2 |
HIP 1690 |
13.16 |
| 2026-02-23 12:00 |
00:22:11.50 |
+28:57:23.1 |
HIP 1690 |
13.47 |
| 2026-02-24 00:00 |
00:22:12.96 |
+28:57:25.2 |
HIP 1690 |
13.79 |