| 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) |
| 2026-05-12 00:00 |
09:04:31.17 |
-69:37:16.4 |
HIP 44650 |
7.62 |
| 2026-05-12 12:00 |
09:04:31.70 |
-69:36:50.1 |
HIP 44650 |
7.43 |
| 2026-05-13 00:00 |
09:04:32.27 |
-69:36:23.8 |
HIP 44650 |
7.25 |
| 2026-05-13 12:00 |
09:04:32.89 |
-69:35:57.5 |
HIP 44650 |
7.10 |
| 2026-05-14 00:00 |
09:04:33.54 |
-69:35:31.4 |
HIP 44650 |
6.97 |
| 2026-05-14 12:00 |
09:04:34.24 |
-69:35:05.2 |
HIP 44650 |
6.86 |
| 2026-05-15 00:00 |
09:04:34.97 |
-69:34:39.1 |
HIP 44650 |
6.78 |
| 2026-05-15 12:00 |
09:04:35.75 |
-69:34:13.0 |
HIP 44650 |
6.71 |
| 2026-05-16 00:00 |
09:04:36.57 |
-69:33:47.0 |
HIP 44650 |
6.68 |
| 2026-05-16 12:00 |
09:04:37.42 |
-69:33:21.0 |
HIP 44650 |
6.67 |
| 2026-05-17 00:00 |
09:04:38.32 |
-69:32:55.1 |
HIP 44650 |
6.68 |
| 2026-05-17 12:00 |
09:04:39.26 |
-69:32:29.3 |
HIP 44650 |
6.72 |
| 2026-05-18 00:00 |
09:04:40.24 |
-69:32:03.5 |
HIP 44650 |
6.78 |
| 2026-05-18 12:00 |
09:04:41.26 |
-69:31:37.7 |
HIP 44650 |
6.87 |
| 2026-05-19 00:00 |
09:04:42.33 |
-69:31:12.0 |
HIP 44650 |
6.98 |
| 2026-05-19 12:00 |
09:04:43.43 |
-69:30:46.4 |
HIP 44650 |
7.11 |
| 2026-05-20 00:00 |
09:04:44.57 |
-69:30:20.8 |
HIP 44650 |
7.26 |
| 2026-05-20 12:00 |
09:04:45.75 |
-69:29:55.3 |
HIP 44650 |
7.43 |
| 2026-05-21 00:00 |
09:04:46.96 |
-69:29:29.9 |
HIP 44650 |
7.62 |
| 2026-05-21 12:00 |
09:04:48.22 |
-69:29:04.6 |
HIP 44650 |
7.83 |
| 2026-05-22 00:00 |
09:04:49.52 |
-69:28:39.3 |
HIP 44650 |
8.05 |
| 2026-05-22 12:00 |
09:04:50.86 |
-69:28:14.1 |
HIP 44650 |
8.28 |
| 2026-05-23 00:00 |
09:04:52.23 |
-69:27:48.9 |
HIP 44650 |
8.53 |
| 2026-05-23 12:00 |
09:04:53.65 |
-69:27:23.9 |
HIP 44650 |
8.79 |
| 2026-05-24 00:00 |
09:04:55.10 |
-69:26:58.9 |
HIP 44650 |
9.06 |
| 2026-05-24 12:00 |
09:04:56.59 |
-69:26:34.0 |
HIP 44650 |
9.34 |
| 2026-05-25 00:00 |
09:04:58.12 |
-69:26:09.1 |
HIP 44650 |
9.63 |
| 2026-05-25 12:00 |
09:04:59.68 |
-69:25:44.4 |
HIP 44650 |
9.92 |
| 2026-05-26 00:00 |
09:05:01.28 |
-69:25:19.7 |
HIP 44650 |
10.23 |
| 2026-05-26 12:00 |
09:05:02.93 |
-69:24:55.2 |
HIP 44650 |
10.53 |
| 2026-05-27 00:00 |
09:05:04.60 |
-69:24:30.7 |
HIP 44650 |
10.85 |
| 2026-05-27 12:00 |
09:05:06.32 |
-69:24:06.3 |
HIP 44650 |
11.17 |
| 2026-05-28 00:00 |
09:05:08.07 |
-69:23:42.0 |
HIP 44650 |
11.50 |
| 2026-05-28 12:00 |
09:05:09.86 |
-69:23:17.8 |
HIP 44650 |
11.83 |
| 2026-05-29 00:00 |
09:05:11.68 |
-69:22:53.7 |
HIP 44650 |
12.16 |
| 2026-05-29 12:00 |
09:05:13.55 |
-69:22:29.7 |
HIP 44650 |
12.50 |
| 2026-05-30 00:00 |
09:05:15.44 |
-69:22:05.7 |
HIP 44650 |
12.84 |
| 2026-05-30 12:00 |
09:05:17.38 |
-69:21:41.9 |
HIP 44650 |
13.18 |
| 2026-05-31 00:00 |
09:05:19.35 |
-69:21:18.2 |
HIP 44650 |
13.53 |
| 2026-05-31 12:00 |
09:05:21.35 |
-69:20:54.6 |
HIP 44650 |
13.88 |
| 2026-06-01 00:00 |
09:05:23.39 |
-69:20:31.1 |
HIP 44650 |
14.23 |
| 2026-06-01 12:00 |
09:05:25.47 |
-69:20:07.7 |
HIP 44650 |
14.58 |
| 2026-06-02 00:00 |
09:05:27.58 |
-69:19:44.4 |
HIP 44650 |
14.94 |