C/1985 R1 (Hartley-Good)
| 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
$$
M_a = (7.907 + 3.169\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
7.907 |
| n |
3.169 |
| 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 |
-14.0075 |
+3.753 |
| 1985-09-21 |
1985-10-03 |
+7.8877 |
-1.021 |
| 1985-10-03 |
1985-12-08 |
-0.5553 |
-0.024 |
| 1985-12-09 |
1986-03-19 |
+13.3819 |
+1.342 |
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 |
09:14:50.32 |
-70:34:40.7 |
HIP 45582 |
17.25 |
| 2026-02-03 12:00 |
09:14:44.97 |
-70:34:41.8 |
HIP 45582 |
17.60 |
| 2026-02-04 00:00 |
09:14:39.62 |
-70:34:42.6 |
HIP 45582 |
17.96 |
| 2026-02-04 12:00 |
09:14:34.27 |
-70:34:43.2 |
HIP 45582 |
18.31 |
| 2026-02-05 00:00 |
09:14:28.92 |
-70:34:43.5 |
HIP 45582 |
18.67 |
| 2026-02-05 12:00 |
09:14:23.56 |
-70:34:43.6 |
HIP 45582 |
19.02 |
| 2026-02-06 00:00 |
09:14:18.21 |
-70:34:43.5 |
HIP 45582 |
19.38 |
| 2026-02-06 12:00 |
09:14:12.86 |
-70:34:43.1 |
HIP 45582 |
19.74 |
| 2026-02-07 00:00 |
09:14:07.50 |
-70:34:42.4 |
HIP 45582 |
20.10 |
| 2026-02-07 12:00 |
09:14:02.15 |
-70:34:41.5 |
HIP 45582 |
20.46 |
| 2026-02-08 00:00 |
09:13:56.80 |
-70:34:40.3 |
HIP 45582 |
20.83 |
| 2026-02-08 12:00 |
09:13:51.45 |
-70:34:38.9 |
HIP 45582 |
21.19 |
| 2026-02-09 00:00 |
09:13:46.11 |
-70:34:37.3 |
HIP 45582 |
21.56 |
| 2026-02-09 12:00 |
09:13:40.77 |
-70:34:35.4 |
HIP 45582 |
21.92 |
| 2026-02-10 00:00 |
09:13:35.43 |
-70:34:33.2 |
HIP 45582 |
22.29 |
| 2026-02-10 12:00 |
09:13:30.09 |
-70:34:30.8 |
HIP 45582 |
22.65 |
| 2026-02-11 00:00 |
09:13:24.76 |
-70:34:28.2 |
HIP 45582 |
23.02 |
| 2026-02-11 12:00 |
09:13:19.44 |
-70:34:25.2 |
HIP 45582 |
23.39 |
| 2026-02-12 00:00 |
09:13:14.12 |
-70:34:22.1 |
HIP 45582 |
23.76 |
| 2026-02-12 12:00 |
09:13:08.80 |
-70:34:18.7 |
HIP 45582 |
24.13 |
| 2026-02-13 00:00 |
09:13:03.49 |
-70:34:15.0 |
HIP 45582 |
24.49 |
| 2026-02-13 12:00 |
09:12:58.19 |
-70:34:11.1 |
HIP 45582 |
24.86 |
| 2026-02-14 00:00 |
09:12:52.90 |
-70:34:07.0 |
HIP 45582 |
25.23 |
| 2026-02-14 12:00 |
09:12:47.61 |
-70:34:02.6 |
HIP 45582 |
25.60 |
| 2026-02-15 00:00 |
09:12:42.33 |
-70:33:58.0 |
HIP 45582 |
25.97 |
| 2026-02-15 12:00 |
09:12:37.06 |
-70:33:53.1 |
HIP 45582 |
26.34 |
| 2026-02-16 00:00 |
09:12:31.80 |
-70:33:48.0 |
HIP 45582 |
26.72 |
| 2026-02-16 12:00 |
09:12:26.55 |
-70:33:42.6 |
HIP 45582 |
27.09 |
| 2026-02-17 00:00 |
09:12:21.31 |
-70:33:37.0 |
HIP 45582 |
27.46 |
| 2026-02-17 12:00 |
09:12:16.08 |
-70:33:31.1 |
HIP 45582 |
27.83 |
| 2026-02-18 00:00 |
09:12:10.86 |
-70:33:25.0 |
HIP 45582 |
28.20 |
| 2026-02-18 12:00 |
09:12:05.65 |
-70:33:18.6 |
HIP 45582 |
28.57 |
| 2026-02-19 00:00 |
09:12:00.46 |
-70:33:12.0 |
HIP 45582 |
28.94 |
| 2026-02-19 12:00 |
09:11:55.27 |
-70:33:05.2 |
HIP 45582 |
29.31 |
| 2026-02-20 00:00 |
09:11:50.10 |
-70:32:58.1 |
HIP 45582 |
29.68 |
| 2026-02-20 12:00 |
09:11:44.95 |
-70:32:50.8 |
HIP 45582 |
30.05 |
| 2026-02-21 00:00 |
09:11:39.80 |
-70:32:43.3 |
HIP 44626 |
30.10 |
| 2026-02-21 12:00 |
09:11:34.67 |
-70:32:35.5 |
HIP 44626 |
29.67 |
| 2026-02-22 00:00 |
09:11:29.56 |
-70:32:27.4 |
HIP 44626 |
29.25 |
| 2026-02-22 12:00 |
09:11:24.46 |
-70:32:19.2 |
HIP 44626 |
28.83 |
| 2026-02-23 00:00 |
09:11:19.38 |
-70:32:10.7 |
HIP 44626 |
28.40 |
| 2026-02-23 12:00 |
09:11:14.31 |
-70:32:01.9 |
HIP 44626 |
27.98 |
| 2026-02-24 00:00 |
09:11:09.26 |
-70:31:52.9 |
HIP 44626 |
27.57 |