| 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 |
9.997 |
| 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 |
+19.0075 |
-13.853 |
| 2000-01-03 |
2000-12-12 |
-2.2203 |
+0.385 |
| 2000-12-15 |
2001-11-05 |
+1.3647 |
-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) |
| 2026-03-26 00:00 |
22:50:52.80 |
+27:42:24.3 |
HIP 112728 |
16.76 |
| 2026-03-26 12:00 |
22:50:55.22 |
+27:42:42.3 |
HIP 112728 |
17.37 |
| 2026-03-27 00:00 |
22:50:57.63 |
+27:43:00.4 |
HIP 112728 |
17.99 |
| 2026-03-27 12:00 |
22:51:00.04 |
+27:43:18.7 |
HIP 112728 |
18.60 |
| 2026-03-28 00:00 |
22:51:02.43 |
+27:43:37.0 |
HIP 112728 |
19.21 |
| 2026-03-28 12:00 |
22:51:04.81 |
+27:43:55.5 |
HIP 112728 |
19.82 |
| 2026-03-29 00:00 |
22:51:07.19 |
+27:44:14.1 |
HIP 112728 |
20.42 |
| 2026-03-29 12:00 |
22:51:09.55 |
+27:44:32.9 |
HIP 112728 |
21.03 |
| 2026-03-30 00:00 |
22:51:11.91 |
+27:44:51.7 |
HIP 112728 |
21.64 |
| 2026-03-30 12:00 |
22:51:14.25 |
+27:45:10.7 |
HIP 112728 |
22.24 |
| 2026-03-31 00:00 |
22:51:16.58 |
+27:45:29.7 |
HIP 112728 |
22.85 |
| 2026-03-31 12:00 |
22:51:18.91 |
+27:45:48.9 |
HIP 112728 |
23.45 |
| 2026-04-01 00:00 |
22:51:21.22 |
+27:46:08.2 |
HIP 112728 |
24.05 |
| 2026-04-01 12:00 |
22:51:23.52 |
+27:46:27.5 |
HIP 112728 |
24.65 |
| 2026-04-02 00:00 |
22:51:25.82 |
+27:46:47.0 |
HIP 112728 |
25.25 |
| 2026-04-02 12:00 |
22:51:28.10 |
+27:47:06.6 |
HIP 112728 |
25.85 |
| 2026-04-03 00:00 |
22:51:30.37 |
+27:47:26.3 |
HIP 113033 |
26.36 |
| 2026-04-03 12:00 |
22:51:32.62 |
+27:47:46.1 |
HIP 113033 |
25.90 |
| 2026-04-04 00:00 |
22:51:34.87 |
+27:48:06.0 |
HIP 113033 |
25.43 |
| 2026-04-04 12:00 |
22:51:37.11 |
+27:48:26.0 |
HIP 113033 |
24.98 |
| 2026-04-05 00:00 |
22:51:39.33 |
+27:48:46.1 |
HIP 113033 |
24.54 |
| 2026-04-05 12:00 |
22:51:41.54 |
+27:49:06.3 |
HIP 113033 |
24.10 |
| 2026-04-06 00:00 |
22:51:43.74 |
+27:49:26.6 |
HIP 113033 |
23.68 |
| 2026-04-06 12:00 |
22:51:45.93 |
+27:49:47.0 |
HIP 113033 |
23.26 |
| 2026-04-07 00:00 |
22:51:48.11 |
+27:50:07.4 |
HIP 113033 |
22.86 |
| 2026-04-07 12:00 |
22:51:50.27 |
+27:50:28.0 |
HIP 113033 |
22.47 |
| 2026-04-08 00:00 |
22:51:52.42 |
+27:50:48.7 |
HIP 113033 |
22.09 |
| 2026-04-08 12:00 |
22:51:54.56 |
+27:51:09.4 |
HIP 113033 |
21.72 |
| 2026-04-09 00:00 |
22:51:56.69 |
+27:51:30.2 |
HIP 113033 |
21.36 |
| 2026-04-09 12:00 |
22:51:58.80 |
+27:51:51.1 |
HIP 113033 |
21.02 |
| 2026-04-10 00:00 |
22:52:00.90 |
+27:52:12.1 |
HIP 113033 |
20.70 |
| 2026-04-10 12:00 |
22:52:02.98 |
+27:52:33.2 |
HIP 113033 |
20.38 |
| 2026-04-11 00:00 |
22:52:05.06 |
+27:52:54.4 |
HIP 113033 |
20.08 |
| 2026-04-11 12:00 |
22:52:07.12 |
+27:53:15.6 |
HIP 113033 |
19.80 |
| 2026-04-12 00:00 |
22:52:09.16 |
+27:53:36.9 |
HIP 113033 |
19.54 |
| 2026-04-12 12:00 |
22:52:11.19 |
+27:53:58.3 |
HIP 113033 |
19.29 |
| 2026-04-13 00:00 |
22:52:13.21 |
+27:54:19.8 |
HIP 113033 |
19.06 |
| 2026-04-13 12:00 |
22:52:15.22 |
+27:54:41.3 |
HIP 113033 |
18.84 |
| 2026-04-14 00:00 |
22:52:17.20 |
+27:55:02.9 |
HIP 113033 |
18.65 |
| 2026-04-14 12:00 |
22:52:19.18 |
+27:55:24.6 |
HIP 113033 |
18.47 |
| 2026-04-15 00:00 |
22:52:21.14 |
+27:55:46.3 |
HIP 113033 |
18.31 |
| 2026-04-15 12:00 |
22:52:23.09 |
+27:56:08.1 |
HIP 113033 |
18.17 |
| 2026-04-16 00:00 |
22:52:25.02 |
+27:56:30.0 |
HIP 113033 |
18.06 |