| Parameter |
Value |
| Designation |
C/1999 T1 (McNaught-Hartley) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2000-12-13T11:19:42.432960Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:30:02Z |
| Obs used |
661 |
| NEO |
- |
| M1 |
8.300 |
| K1 |
7.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2000-11-18.0000000 |
| e |
0.99985577 |
| q (au) |
1.171699 |
| a (au) |
8123.927279 |
| i (deg) |
79.975213 |
| Ω (om, deg) |
182.483007 |
| ω (w, deg) |
344.758001 |
| M (ma, deg) |
359.999966 |
Magnitude
Scatter + Global Linear
$$
M_a = (5.381 + 4.354\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
5.381 |
| n |
4.354 |
| gf |
0.998 |
| gb |
-0.917 |
| k |
0.998 |
| δ90 |
9.996 |
| 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 |
| 1999-10-07 |
2000-01-03 |
+19.0088 |
-13.854 |
| 2000-01-03 |
2000-12-12 |
-2.2204 |
+0.385 |
| 2000-12-15 |
2001-11-05 |
+1.3645 |
-0.126 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-07-29 00:00 |
22:52:05.03 |
+28:55:44.3 |
HIP 112854 |
21.20 |
| 2026-07-29 12:00 |
22:52:02.95 |
+28:55:46.6 |
HIP 112854 |
20.94 |
| 2026-07-30 00:00 |
22:52:00.86 |
+28:55:48.7 |
HIP 112854 |
20.69 |
| 2026-07-30 12:00 |
22:51:58.76 |
+28:55:50.6 |
HIP 112854 |
20.45 |
| 2026-07-31 00:00 |
22:51:56.65 |
+28:55:52.4 |
HIP 112854 |
20.22 |
| 2026-07-31 12:00 |
22:51:54.52 |
+28:55:53.9 |
HIP 112854 |
20.00 |
| 2026-08-01 00:00 |
22:51:52.38 |
+28:55:55.2 |
HIP 112854 |
19.78 |
| 2026-08-01 12:00 |
22:51:50.23 |
+28:55:56.3 |
HIP 112854 |
19.58 |
| 2026-08-02 00:00 |
22:51:48.07 |
+28:55:57.1 |
HIP 112854 |
19.39 |
| 2026-08-02 12:00 |
22:51:45.89 |
+28:55:57.8 |
HIP 112854 |
19.22 |
| 2026-08-03 00:00 |
22:51:43.70 |
+28:55:58.3 |
HIP 112854 |
19.05 |
| 2026-08-03 12:00 |
22:51:41.50 |
+28:55:58.5 |
HIP 112854 |
18.90 |
| 2026-08-04 00:00 |
22:51:39.29 |
+28:55:58.6 |
HIP 112854 |
18.76 |
| 2026-08-04 12:00 |
22:51:37.07 |
+28:55:58.4 |
HIP 112854 |
18.64 |
| 2026-08-05 00:00 |
22:51:34.83 |
+28:55:58.0 |
HIP 112854 |
18.53 |
| 2026-08-05 12:00 |
22:51:32.59 |
+28:55:57.4 |
HIP 112854 |
18.44 |
| 2026-08-06 00:00 |
22:51:30.33 |
+28:55:56.6 |
HIP 112854 |
18.36 |
| 2026-08-06 12:00 |
22:51:28.06 |
+28:55:55.6 |
HIP 112854 |
18.30 |
| 2026-08-07 00:00 |
22:51:25.78 |
+28:55:54.4 |
HIP 112854 |
18.26 |
| 2026-08-07 12:00 |
22:51:23.49 |
+28:55:53.0 |
HIP 112854 |
18.23 |
| 2026-08-08 00:00 |
22:51:21.19 |
+28:55:51.3 |
HIP 112854 |
18.22 |
| 2026-08-08 12:00 |
22:51:18.88 |
+28:55:49.4 |
HIP 112854 |
18.22 |
| 2026-08-09 00:00 |
22:51:16.57 |
+28:55:47.4 |
HIP 112854 |
18.25 |
| 2026-08-09 12:00 |
22:51:14.24 |
+28:55:45.1 |
HIP 112854 |
18.29 |
| 2026-08-10 00:00 |
22:51:11.90 |
+28:55:42.6 |
HIP 112854 |
18.35 |
| 2026-08-10 12:00 |
22:51:09.55 |
+28:55:39.8 |
HIP 112733 |
18.00 |
| 2026-08-11 00:00 |
22:51:07.19 |
+28:55:36.9 |
HIP 112733 |
17.49 |
| 2026-08-11 12:00 |
22:51:04.82 |
+28:55:33.8 |
HIP 112733 |
16.97 |
| 2026-08-12 00:00 |
22:51:02.45 |
+28:55:30.4 |
HIP 112733 |
16.46 |
| 2026-08-12 12:00 |
22:51:00.06 |
+28:55:26.8 |
HIP 112733 |
15.94 |
| 2026-08-13 00:00 |
22:50:57.67 |
+28:55:23.0 |
HIP 112733 |
15.43 |
| 2026-08-13 12:00 |
22:50:55.27 |
+28:55:19.0 |
HIP 112733 |
14.91 |
| 2026-08-14 00:00 |
22:50:52.86 |
+28:55:14.8 |
HIP 112733 |
14.39 |
| 2026-08-14 12:00 |
22:50:50.44 |
+28:55:10.4 |
HIP 112733 |
13.87 |
| 2026-08-15 00:00 |
22:50:48.01 |
+28:55:05.8 |
HIP 112733 |
13.35 |
| 2026-08-15 12:00 |
22:50:45.58 |
+28:55:00.9 |
HIP 112733 |
12.84 |
| 2026-08-16 00:00 |
22:50:43.14 |
+28:54:55.8 |
HIP 112733 |
12.32 |
| 2026-08-16 12:00 |
22:50:40.69 |
+28:54:50.6 |
HIP 112733 |
11.80 |
| 2026-08-17 00:00 |
22:50:38.24 |
+28:54:45.1 |
HIP 112733 |
11.29 |
| 2026-08-17 12:00 |
22:50:35.77 |
+28:54:39.4 |
HIP 112733 |
10.77 |
| 2026-08-18 00:00 |
22:50:33.31 |
+28:54:33.5 |
HIP 112733 |
10.26 |
| 2026-08-18 12:00 |
22:50:30.83 |
+28:54:27.4 |
HIP 112733 |
9.76 |
| 2026-08-19 00:00 |
22:50:28.35 |
+28:54:21.0 |
HIP 112733 |
9.25 |