| Parameter |
Value |
| Designation |
C/2008 A1 (McNaught) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2008-09-29T02:59:09.844800Z |
| Orbit solution date (soln_date, UTC) |
2021-04-16T12:07:02Z |
| Obs used |
906 |
| NEO |
- |
| M1 |
8.100 |
| K1 |
10.000 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2008-09-26.0000000 |
| e |
1.00023047 |
| q (au) |
1.073075 |
| a (au) |
-4655.992023 |
| i (deg) |
82.549175 |
| Ω (om, deg) |
277.883699 |
| ω (w, deg) |
348.473258 |
| M (ma, deg) |
-0.000010 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.584 + 3.102\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.584 |
| n |
3.102 |
| gf |
0.998 |
| gb |
-0.500 |
| k |
0.800 |
| δ90 |
8.390 |
| 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 |
| 2008-01-10 |
2008-09-28 |
+4.7194 |
-3.531 |
| 2008-09-29 |
2008-11-02 |
+10.5269 |
-3.006 |
| 2008-11-02 |
2010-01-17 |
+3.3602 |
-1.676 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-06-01 00:00 |
06:15:53.88 |
+53:32:32.0 |
HIP 29795 |
5.57 |
| 2026-06-01 12:00 |
06:15:58.66 |
+53:32:19.9 |
HIP 29795 |
4.90 |
| 2026-06-02 00:00 |
06:16:03.45 |
+53:32:08.0 |
HIP 29795 |
4.24 |
| 2026-06-02 12:00 |
06:16:08.26 |
+53:31:56.3 |
HIP 29795 |
3.62 |
| 2026-06-03 00:00 |
06:16:13.08 |
+53:31:44.8 |
HIP 29795 |
3.06 |
| 2026-06-03 12:00 |
06:16:17.92 |
+53:31:33.4 |
HIP 29795 |
2.58 |
| 2026-06-04 00:00 |
06:16:22.77 |
+53:31:22.2 |
HIP 29795 |
2.26 |
| 2026-06-04 12:00 |
06:16:27.63 |
+53:31:11.2 |
HIP 29795 |
2.17 |
| 2026-06-05 00:00 |
06:16:32.51 |
+53:31:00.3 |
HIP 29795 |
2.33 |
| 2026-06-05 12:00 |
06:16:37.40 |
+53:30:49.6 |
HIP 29795 |
2.69 |
| 2026-06-06 00:00 |
06:16:42.31 |
+53:30:39.1 |
HIP 29795 |
3.20 |
| 2026-06-06 12:00 |
06:16:47.22 |
+53:30:28.7 |
HIP 29795 |
3.79 |
| 2026-06-07 00:00 |
06:16:52.15 |
+53:30:18.5 |
HIP 29795 |
4.43 |
| 2026-06-07 12:00 |
06:16:57.10 |
+53:30:08.5 |
HIP 29795 |
5.11 |
| 2026-06-08 00:00 |
06:17:02.05 |
+53:29:58.7 |
HIP 29795 |
5.81 |
| 2026-06-08 12:00 |
06:17:07.01 |
+53:29:49.0 |
HIP 29795 |
6.52 |
| 2026-06-09 00:00 |
06:17:11.99 |
+53:29:39.5 |
HIP 29795 |
7.24 |
| 2026-06-09 12:00 |
06:17:16.97 |
+53:29:30.2 |
HIP 29795 |
7.97 |
| 2026-06-10 00:00 |
06:17:21.97 |
+53:29:21.0 |
HIP 29795 |
8.71 |
| 2026-06-10 12:00 |
06:17:26.98 |
+53:29:12.1 |
HIP 29795 |
9.45 |
| 2026-06-11 00:00 |
06:17:31.99 |
+53:29:03.3 |
HIP 29795 |
10.20 |
| 2026-06-11 12:00 |
06:17:37.02 |
+53:28:54.6 |
HIP 29795 |
10.95 |
| 2026-06-12 00:00 |
06:17:42.05 |
+53:28:46.2 |
HIP 29795 |
11.70 |
| 2026-06-12 12:00 |
06:17:47.10 |
+53:28:37.9 |
HIP 29935 |
12.05 |
| 2026-06-13 00:00 |
06:17:52.15 |
+53:28:29.8 |
HIP 29935 |
12.02 |
| 2026-06-13 12:00 |
06:17:57.21 |
+53:28:21.9 |
HIP 29935 |
12.03 |
| 2026-06-14 00:00 |
06:18:02.28 |
+53:28:14.2 |
HIP 29935 |
12.08 |
| 2026-06-14 12:00 |
06:18:07.35 |
+53:28:06.6 |
HIP 29935 |
12.18 |
| 2026-06-15 00:00 |
06:18:12.43 |
+53:27:59.3 |
HIP 29935 |
12.32 |
| 2026-06-15 12:00 |
06:18:17.52 |
+53:27:52.1 |
HIP 29935 |
12.50 |
| 2026-06-16 00:00 |
06:18:22.62 |
+53:27:45.0 |
HIP 29935 |
12.73 |
| 2026-06-16 12:00 |
06:18:27.72 |
+53:27:38.2 |
HIP 29935 |
12.99 |
| 2026-06-17 00:00 |
06:18:32.83 |
+53:27:31.5 |
HIP 29935 |
13.29 |
| 2026-06-17 12:00 |
06:18:37.94 |
+53:27:25.1 |
HIP 29935 |
13.63 |
| 2026-06-18 00:00 |
06:18:43.06 |
+53:27:18.8 |
HIP 29935 |
13.99 |
| 2026-06-18 12:00 |
06:18:48.18 |
+53:27:12.6 |
HIP 29935 |
14.39 |
| 2026-06-19 00:00 |
06:18:53.31 |
+53:27:06.7 |
HIP 29935 |
14.81 |
| 2026-06-19 12:00 |
06:18:58.44 |
+53:27:00.9 |
HIP 29935 |
15.26 |
| 2026-06-20 00:00 |
06:19:03.57 |
+53:26:55.3 |
HIP 29935 |
15.73 |
| 2026-06-20 12:00 |
06:19:08.71 |
+53:26:49.9 |
HIP 29935 |
16.22 |
| 2026-06-21 00:00 |
06:19:13.85 |
+53:26:44.7 |
HIP 29935 |
16.72 |
| 2026-06-21 12:00 |
06:19:18.99 |
+53:26:39.7 |
HIP 29935 |
17.25 |
| 2026-06-22 00:00 |
06:19:24.14 |
+53:26:34.8 |
HIP 29935 |
17.79 |