| 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) |
| 2026-06-01 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 |
| 2026-06-02 12:00 |
09:05:29.73 |
-69:19:21.2 |
HIP 44650 |
15.29 |
| 2026-06-03 00:00 |
09:05:31.91 |
-69:18:58.1 |
HIP 44650 |
15.65 |
| 2026-06-03 12:00 |
09:05:34.13 |
-69:18:35.1 |
HIP 44650 |
16.01 |
| 2026-06-04 00:00 |
09:05:36.38 |
-69:18:12.2 |
HIP 44650 |
16.37 |
| 2026-06-04 12:00 |
09:05:38.66 |
-69:17:49.5 |
HIP 44650 |
16.73 |
| 2026-06-05 00:00 |
09:05:40.98 |
-69:17:26.8 |
HIP 44650 |
17.10 |
| 2026-06-05 12:00 |
09:05:43.33 |
-69:17:04.3 |
HIP 44650 |
17.46 |
| 2026-06-06 00:00 |
09:05:45.72 |
-69:16:41.9 |
HIP 44650 |
17.83 |
| 2026-06-06 12:00 |
09:05:48.14 |
-69:16:19.6 |
HIP 44650 |
18.19 |
| 2026-06-07 00:00 |
09:05:50.59 |
-69:15:57.5 |
HIP 44650 |
18.56 |
| 2026-06-07 12:00 |
09:05:53.07 |
-69:15:35.4 |
HIP 44650 |
18.92 |
| 2026-06-08 00:00 |
09:05:55.59 |
-69:15:13.5 |
HIP 44650 |
19.29 |
| 2026-06-08 12:00 |
09:05:58.15 |
-69:14:51.7 |
HIP 44650 |
19.66 |
| 2026-06-09 00:00 |
09:06:00.73 |
-69:14:30.0 |
HIP 44650 |
20.03 |
| 2026-06-09 12:00 |
09:06:03.35 |
-69:14:08.5 |
HIP 44650 |
20.39 |
| 2026-06-10 00:00 |
09:06:06.00 |
-69:13:47.1 |
HIP 44650 |
20.76 |
| 2026-06-10 12:00 |
09:06:08.68 |
-69:13:25.8 |
HIP 44650 |
21.13 |
| 2026-06-11 00:00 |
09:06:11.39 |
-69:13:04.7 |
HIP 44650 |
21.50 |
| 2026-06-11 12:00 |
09:06:14.13 |
-69:12:43.7 |
HIP 44650 |
21.87 |
| 2026-06-12 00:00 |
09:06:16.91 |
-69:12:22.8 |
HIP 44650 |
22.24 |
| 2026-06-12 12:00 |
09:06:19.72 |
-69:12:02.1 |
HIP 44650 |
22.60 |
| 2026-06-13 00:00 |
09:06:22.55 |
-69:11:41.5 |
HIP 44650 |
22.97 |
| 2026-06-13 12:00 |
09:06:25.42 |
-69:11:21.0 |
HIP 44650 |
23.34 |
| 2026-06-14 00:00 |
09:06:28.32 |
-69:11:00.7 |
HIP 44650 |
23.71 |
| 2026-06-14 12:00 |
09:06:31.25 |
-69:10:40.6 |
HIP 44650 |
24.08 |
| 2026-06-15 00:00 |
09:06:34.21 |
-69:10:20.5 |
HIP 44650 |
24.45 |
| 2026-06-15 12:00 |
09:06:37.20 |
-69:10:00.7 |
HIP 44650 |
24.81 |
| 2026-06-16 00:00 |
09:06:40.22 |
-69:09:40.9 |
HIP 44786 |
24.97 |
| 2026-06-16 12:00 |
09:06:43.27 |
-69:09:21.4 |
HIP 44786 |
24.59 |
| 2026-06-17 00:00 |
09:06:46.34 |
-69:09:02.0 |
HIP 44786 |
24.22 |
| 2026-06-17 12:00 |
09:06:49.45 |
-69:08:42.7 |
HIP 44786 |
23.85 |
| 2026-06-18 00:00 |
09:06:52.58 |
-69:08:23.6 |
HIP 44786 |
23.49 |
| 2026-06-18 12:00 |
09:06:55.75 |
-69:08:04.6 |
HIP 44786 |
23.12 |
| 2026-06-19 00:00 |
09:06:58.94 |
-69:07:45.8 |
HIP 44786 |
22.77 |
| 2026-06-19 12:00 |
09:07:02.15 |
-69:07:27.1 |
HIP 44786 |
22.42 |
| 2026-06-20 00:00 |
09:07:05.40 |
-69:07:08.7 |
HIP 44786 |
22.07 |
| 2026-06-20 12:00 |
09:07:08.67 |
-69:06:50.3 |
HIP 44786 |
21.73 |
| 2026-06-21 00:00 |
09:07:11.97 |
-69:06:32.2 |
HIP 44786 |
21.39 |
| 2026-06-21 12:00 |
09:07:15.30 |
-69:06:14.2 |
HIP 44786 |
21.06 |
| 2026-06-22 00:00 |
09:07:18.65 |
-69:05:56.3 |
HIP 44786 |
20.73 |