| Parameter |
Value |
| Designation |
C/1987 U3 (McNaught) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1987-12-11T22:32:44.332800Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:36Z |
| Obs used |
106 |
| NEO |
- |
| M1 |
6.100 |
| K1 |
17.250 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1988-01-08.0000000 |
| e |
0.99855807 |
| q (au) |
0.841167 |
| a (au) |
583.363126 |
| i (deg) |
97.126481 |
| Ω (om, deg) |
261.341785 |
| ω (w, deg) |
17.409142 |
| M (ma, deg) |
0.001893 |
Magnitude
Scatter + Global Linear
$$
M_a = (4.978 + 3.538\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
4.978 |
| n |
3.538 |
| 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 |
| 1987-12-27 |
1988-02-01 |
-7.4131 |
+0.143 |
| 1988-02-01 |
1988-02-18 |
+3.8294 |
-0.662 |
| 1988-02-18 |
1988-03-22 |
+3.4165 |
-0.549 |
| 1988-03-22 |
1988-05-10 |
-6.7830 |
+2.088 |
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 |
05:19:01.70 |
+18:37:43.1 |
HIP 24910 |
18.89 |
| 2026-05-12 12:00 |
05:19:03.39 |
+18:37:45.3 |
HIP 24910 |
18.49 |
| 2026-05-13 00:00 |
05:19:05.09 |
+18:37:47.5 |
HIP 24910 |
18.10 |
| 2026-05-13 12:00 |
05:19:06.79 |
+18:37:49.7 |
HIP 24910 |
17.70 |
| 2026-05-14 00:00 |
05:19:08.51 |
+18:37:51.9 |
HIP 24910 |
17.30 |
| 2026-05-14 12:00 |
05:19:10.23 |
+18:37:54.1 |
HIP 24910 |
16.90 |
| 2026-05-15 00:00 |
05:19:11.96 |
+18:37:56.2 |
HIP 24910 |
16.50 |
| 2026-05-15 12:00 |
05:19:13.69 |
+18:37:58.3 |
HIP 24910 |
16.10 |
| 2026-05-16 00:00 |
05:19:15.44 |
+18:38:00.5 |
HIP 24910 |
15.70 |
| 2026-05-16 12:00 |
05:19:17.19 |
+18:38:02.6 |
HIP 24910 |
15.29 |
| 2026-05-17 00:00 |
05:19:18.94 |
+18:38:04.7 |
HIP 24910 |
14.89 |
| 2026-05-17 12:00 |
05:19:20.71 |
+18:38:06.8 |
HIP 24910 |
14.48 |
| 2026-05-18 00:00 |
05:19:22.48 |
+18:38:08.9 |
HIP 24910 |
14.08 |
| 2026-05-18 12:00 |
05:19:24.25 |
+18:38:11.0 |
HIP 24910 |
13.67 |
| 2026-05-19 00:00 |
05:19:26.04 |
+18:38:13.0 |
HIP 24910 |
13.26 |
| 2026-05-19 12:00 |
05:19:27.83 |
+18:38:15.1 |
HIP 24910 |
12.85 |
| 2026-05-20 00:00 |
05:19:29.62 |
+18:38:17.1 |
HIP 24910 |
12.44 |
| 2026-05-20 12:00 |
05:19:31.42 |
+18:38:19.1 |
HIP 24910 |
12.03 |
| 2026-05-21 00:00 |
05:19:33.23 |
+18:38:21.2 |
HIP 24910 |
11.63 |
| 2026-05-21 12:00 |
05:19:35.04 |
+18:38:23.2 |
HIP 24910 |
11.22 |
| 2026-05-22 00:00 |
05:19:36.86 |
+18:38:25.1 |
HIP 24910 |
10.81 |
| 2026-05-22 12:00 |
05:19:38.68 |
+18:38:27.1 |
HIP 24910 |
10.40 |
| 2026-05-23 00:00 |
05:19:40.51 |
+18:38:29.1 |
HIP 24910 |
9.99 |
| 2026-05-23 12:00 |
05:19:42.35 |
+18:38:31.0 |
HIP 24910 |
9.59 |
| 2026-05-24 00:00 |
05:19:44.18 |
+18:38:33.0 |
HIP 24910 |
9.19 |
| 2026-05-24 12:00 |
05:19:46.03 |
+18:38:34.9 |
HIP 24910 |
8.78 |
| 2026-05-25 00:00 |
05:19:47.88 |
+18:38:36.8 |
HIP 24910 |
8.38 |
| 2026-05-25 12:00 |
05:19:49.73 |
+18:38:38.7 |
HIP 24910 |
7.99 |
| 2026-05-26 00:00 |
05:19:51.59 |
+18:38:40.6 |
HIP 24910 |
7.60 |
| 2026-05-26 12:00 |
05:19:53.45 |
+18:38:42.4 |
HIP 24910 |
7.21 |
| 2026-05-27 00:00 |
05:19:55.32 |
+18:38:44.3 |
HIP 24910 |
6.83 |
| 2026-05-27 12:00 |
05:19:57.19 |
+18:38:46.1 |
HIP 24910 |
6.45 |
| 2026-05-28 00:00 |
05:19:59.06 |
+18:38:47.9 |
HIP 24910 |
6.08 |
| 2026-05-28 12:00 |
05:20:00.94 |
+18:38:49.7 |
HIP 24910 |
5.73 |
| 2026-05-29 00:00 |
05:20:02.82 |
+18:38:51.5 |
HIP 24910 |
5.38 |
| 2026-05-29 12:00 |
05:20:04.71 |
+18:38:53.3 |
HIP 24910 |
5.05 |
| 2026-05-30 00:00 |
05:20:06.59 |
+18:38:55.0 |
HIP 24910 |
4.74 |
| 2026-05-30 12:00 |
05:20:08.49 |
+18:38:56.8 |
HIP 24910 |
4.45 |
| 2026-05-31 00:00 |
05:20:10.38 |
+18:38:58.5 |
HIP 24910 |
4.19 |
| 2026-05-31 12:00 |
05:20:12.28 |
+18:39:00.2 |
HIP 24910 |
3.97 |
| 2026-06-01 00:00 |
05:20:14.18 |
+18:39:01.9 |
HIP 24910 |
3.78 |
| 2026-06-01 12:00 |
05:20:16.09 |
+18:39:03.6 |
HIP 24910 |
3.64 |
| 2026-06-02 00:00 |
05:20:17.99 |
+18:39:05.3 |
HIP 24910 |
3.55 |