| Parameter |
Value |
| Designation |
C/1985 R1 (Hartley-Good) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1985-12-09T02:47:23.835840Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:33Z |
| Obs used |
165 |
| NEO |
- |
| M1 |
8.500 |
| K1 |
17.750 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1985-11-02.0000000 |
| e |
0.99988722 |
| q (au) |
0.694581 |
| a (au) |
6158.910454 |
| i (deg) |
79.929544 |
| Ω (om, deg) |
358.395879 |
| ω (w, deg) |
87.032512 |
| M (ma, deg) |
359.999924 |
Magnitude
Scatter + Global Linear
$$
M_a = (7.908 + 3.182\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
7.908 |
| n |
3.182 |
| 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 |
| 1985-08-21 |
1985-09-21 |
-14.0412 |
+3.752 |
| 1985-09-21 |
1985-10-03 |
+7.8539 |
-1.023 |
| 1985-10-03 |
1985-12-08 |
-0.5890 |
-0.025 |
| 1985-12-09 |
1986-03-19 |
+13.0977 |
+1.300 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-20 00:00 |
09:20:02.66 |
-69:06:18.2 |
HIP 45862 |
13.16 |
| 2026-09-20 12:00 |
09:20:06.23 |
-69:06:36.5 |
HIP 45862 |
12.75 |
| 2026-09-21 00:00 |
09:20:09.77 |
-69:06:54.8 |
HIP 45862 |
12.34 |
| 2026-09-21 12:00 |
09:20:13.28 |
-69:07:13.4 |
HIP 45862 |
11.94 |
| 2026-09-22 00:00 |
09:20:16.78 |
-69:07:32.1 |
HIP 45862 |
11.53 |
| 2026-09-22 12:00 |
09:20:20.24 |
-69:07:50.9 |
HIP 45862 |
11.13 |
| 2026-09-23 00:00 |
09:20:23.68 |
-69:08:10.0 |
HIP 45862 |
10.73 |
| 2026-09-23 12:00 |
09:20:27.09 |
-69:08:29.1 |
HIP 45862 |
10.33 |
| 2026-09-24 00:00 |
09:20:30.48 |
-69:08:48.5 |
HIP 45862 |
9.93 |
| 2026-09-24 12:00 |
09:20:33.84 |
-69:09:08.0 |
HIP 45862 |
9.53 |
| 2026-09-25 00:00 |
09:20:37.18 |
-69:09:27.6 |
HIP 45862 |
9.13 |
| 2026-09-25 12:00 |
09:20:40.48 |
-69:09:47.4 |
HIP 45862 |
8.74 |
| 2026-09-26 00:00 |
09:20:43.76 |
-69:10:07.4 |
HIP 45862 |
8.35 |
| 2026-09-26 12:00 |
09:20:47.02 |
-69:10:27.5 |
HIP 45862 |
7.96 |
| 2026-09-27 00:00 |
09:20:50.24 |
-69:10:47.7 |
HIP 45862 |
7.58 |
| 2026-09-27 12:00 |
09:20:53.44 |
-69:11:08.1 |
HIP 45862 |
7.20 |
| 2026-09-28 00:00 |
09:20:56.61 |
-69:11:28.7 |
HIP 45862 |
6.83 |
| 2026-09-28 12:00 |
09:20:59.75 |
-69:11:49.4 |
HIP 45862 |
6.46 |
| 2026-09-29 00:00 |
09:21:02.86 |
-69:12:10.2 |
HIP 45862 |
6.10 |
| 2026-09-29 12:00 |
09:21:05.95 |
-69:12:31.2 |
HIP 45862 |
5.75 |
| 2026-09-30 00:00 |
09:21:09.00 |
-69:12:52.3 |
HIP 45862 |
5.41 |
| 2026-09-30 12:00 |
09:21:12.03 |
-69:13:13.6 |
HIP 45862 |
5.09 |
| 2026-10-01 00:00 |
09:21:15.02 |
-69:13:35.0 |
HIP 45862 |
4.78 |
| 2026-10-01 12:00 |
09:21:17.99 |
-69:13:56.5 |
HIP 45862 |
4.49 |
| 2026-10-02 00:00 |
09:21:20.93 |
-69:14:18.2 |
HIP 45862 |
4.23 |
| 2026-10-02 12:00 |
09:21:23.83 |
-69:14:40.1 |
HIP 45862 |
3.99 |
| 2026-10-03 00:00 |
09:21:26.71 |
-69:15:02.0 |
HIP 45862 |
3.79 |
| 2026-10-03 12:00 |
09:21:29.55 |
-69:15:24.1 |
HIP 45862 |
3.63 |
| 2026-10-04 00:00 |
09:21:32.37 |
-69:15:46.3 |
HIP 45862 |
3.52 |
| 2026-10-04 12:00 |
09:21:35.15 |
-69:16:08.7 |
HIP 45862 |
3.45 |
| 2026-10-05 00:00 |
09:21:37.90 |
-69:16:31.2 |
HIP 45862 |
3.44 |
| 2026-10-05 12:00 |
09:21:40.62 |
-69:16:53.8 |
HIP 45862 |
3.49 |
| 2026-10-06 00:00 |
09:21:43.31 |
-69:17:16.5 |
HIP 45862 |
3.58 |
| 2026-10-06 12:00 |
09:21:45.96 |
-69:17:39.4 |
HIP 45862 |
3.73 |
| 2026-10-07 00:00 |
09:21:48.59 |
-69:18:02.4 |
HIP 45862 |
3.91 |
| 2026-10-07 12:00 |
09:21:51.18 |
-69:18:25.5 |
HIP 45862 |
4.14 |
| 2026-10-08 00:00 |
09:21:53.73 |
-69:18:48.7 |
HIP 45862 |
4.39 |
| 2026-10-08 12:00 |
09:21:56.26 |
-69:19:12.1 |
HIP 45862 |
4.68 |
| 2026-10-09 00:00 |
09:21:58.75 |
-69:19:35.6 |
HIP 45862 |
4.98 |
| 2026-10-09 12:00 |
09:22:01.20 |
-69:19:59.2 |
HIP 45862 |
5.30 |
| 2026-10-10 00:00 |
09:22:03.62 |
-69:20:22.9 |
HIP 45862 |
5.64 |
| 2026-10-10 12:00 |
09:22:06.01 |
-69:20:46.7 |
HIP 45862 |
5.99 |
| 2026-10-11 00:00 |
09:22:08.37 |
-69:21:10.6 |
HIP 45862 |
6.35 |