| 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) |
| 2026-03-26 00:00 |
09:06:50.14 |
-70:16:30.5 |
HIP 44663 |
4.59 |
| 2026-03-26 12:00 |
09:06:46.77 |
-70:16:09.5 |
HIP 44663 |
4.16 |
| 2026-03-27 00:00 |
09:06:43.43 |
-70:15:48.5 |
HIP 44663 |
3.73 |
| 2026-03-27 12:00 |
09:06:40.13 |
-70:15:27.3 |
HIP 44663 |
3.32 |
| 2026-03-28 00:00 |
09:06:36.87 |
-70:15:05.9 |
HIP 44663 |
2.91 |
| 2026-03-28 12:00 |
09:06:33.64 |
-70:14:44.4 |
HIP 44663 |
2.53 |
| 2026-03-29 00:00 |
09:06:30.46 |
-70:14:22.8 |
HIP 44663 |
2.17 |
| 2026-03-29 12:00 |
09:06:27.31 |
-70:14:01.0 |
HIP 44663 |
1.86 |
| 2026-03-30 00:00 |
09:06:24.19 |
-70:13:39.1 |
HIP 44663 |
1.61 |
| 2026-03-30 12:00 |
09:06:21.12 |
-70:13:17.1 |
HIP 44663 |
1.47 |
| 2026-03-31 00:00 |
09:06:18.08 |
-70:12:54.9 |
HIP 44663 |
1.47 |
| 2026-03-31 12:00 |
09:06:15.09 |
-70:12:32.6 |
HIP 44663 |
1.60 |
| 2026-04-01 00:00 |
09:06:12.13 |
-70:12:10.2 |
HIP 44663 |
1.84 |
| 2026-04-01 12:00 |
09:06:09.21 |
-70:11:47.6 |
HIP 44663 |
2.15 |
| 2026-04-02 00:00 |
09:06:06.33 |
-70:11:24.9 |
HIP 44663 |
2.50 |
| 2026-04-02 12:00 |
09:06:03.49 |
-70:11:02.1 |
HIP 44663 |
2.88 |
| 2026-04-03 00:00 |
09:06:00.68 |
-70:10:39.2 |
HIP 44663 |
3.29 |
| 2026-04-03 12:00 |
09:05:57.92 |
-70:10:16.1 |
HIP 44663 |
3.70 |
| 2026-04-04 00:00 |
09:05:55.20 |
-70:09:52.9 |
HIP 44663 |
4.12 |
| 2026-04-04 12:00 |
09:05:52.51 |
-70:09:29.7 |
HIP 44663 |
4.55 |
| 2026-04-05 00:00 |
09:05:49.87 |
-70:09:06.3 |
HIP 44663 |
4.99 |
| 2026-04-05 12:00 |
09:05:47.27 |
-70:08:42.8 |
HIP 44663 |
5.42 |
| 2026-04-06 00:00 |
09:05:44.70 |
-70:08:19.1 |
HIP 44663 |
5.86 |
| 2026-04-06 12:00 |
09:05:42.18 |
-70:07:55.4 |
HIP 44663 |
6.31 |
| 2026-04-07 00:00 |
09:05:39.69 |
-70:07:31.6 |
HIP 44663 |
6.75 |
| 2026-04-07 12:00 |
09:05:37.25 |
-70:07:07.6 |
HIP 44663 |
7.19 |
| 2026-04-08 00:00 |
09:05:34.85 |
-70:06:43.6 |
HIP 44663 |
7.64 |
| 2026-04-08 12:00 |
09:05:32.49 |
-70:06:19.4 |
HIP 44663 |
8.09 |
| 2026-04-09 00:00 |
09:05:30.17 |
-70:05:55.2 |
HIP 44663 |
8.53 |
| 2026-04-09 12:00 |
09:05:27.89 |
-70:05:30.8 |
HIP 44663 |
8.98 |
| 2026-04-10 00:00 |
09:05:25.65 |
-70:05:06.4 |
HIP 44663 |
9.43 |
| 2026-04-10 12:00 |
09:05:23.46 |
-70:04:41.8 |
HIP 44663 |
9.88 |
| 2026-04-11 00:00 |
09:05:21.30 |
-70:04:17.2 |
HIP 44663 |
10.33 |
| 2026-04-11 12:00 |
09:05:19.19 |
-70:03:52.5 |
HIP 44663 |
10.78 |
| 2026-04-12 00:00 |
09:05:17.12 |
-70:03:27.7 |
HIP 44663 |
11.23 |
| 2026-04-12 12:00 |
09:05:15.09 |
-70:03:02.8 |
HIP 44663 |
11.68 |
| 2026-04-13 00:00 |
09:05:13.10 |
-70:02:37.8 |
HIP 44663 |
12.13 |
| 2026-04-13 12:00 |
09:05:11.16 |
-70:02:12.7 |
HIP 44663 |
12.58 |
| 2026-04-14 00:00 |
09:05:09.26 |
-70:01:47.6 |
HIP 44663 |
13.02 |
| 2026-04-14 12:00 |
09:05:07.40 |
-70:01:22.4 |
HIP 44663 |
13.47 |
| 2026-04-15 00:00 |
09:05:05.58 |
-70:00:57.1 |
HIP 44663 |
13.92 |
| 2026-04-15 12:00 |
09:05:03.80 |
-70:00:31.7 |
HIP 44663 |
14.37 |
| 2026-04-16 00:00 |
09:05:02.07 |
-70:00:06.3 |
HIP 44663 |
14.82 |