C/2008 A1 (McNaught)
| 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
$$
M_a = (10.585 + 3.112\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.585 |
| n |
3.112 |
| gf |
1.000 |
| gb |
-0.500 |
| k |
0.800 |
| δ90 |
9.762 |
| 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 |
+4.7115 |
-3.532 |
| 2008-09-29 |
2008-11-02 |
+10.1520 |
-2.982 |
| 2008-11-02 |
2010-01-17 |
+3.5913 |
-1.719 |
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 |
06:13:08.96 |
+55:00:47.8 |
HIP 29538 |
34.40 |
| 2026-02-03 12:00 |
06:13:04.60 |
+55:00:29.4 |
HIP 29538 |
34.76 |
| 2026-02-04 00:00 |
06:13:00.27 |
+55:00:10.8 |
HIP 29538 |
35.13 |
| 2026-02-04 12:00 |
06:12:55.99 |
+54:59:52.1 |
HIP 29538 |
35.52 |
| 2026-02-05 00:00 |
06:12:51.74 |
+54:59:33.2 |
HIP 29538 |
35.91 |
| 2026-02-05 12:00 |
06:12:47.52 |
+54:59:14.1 |
HIP 29538 |
36.31 |
| 2026-02-06 00:00 |
06:12:43.35 |
+54:58:54.9 |
HIP 29538 |
36.73 |
| 2026-02-06 12:00 |
06:12:39.21 |
+54:58:35.4 |
HIP 29538 |
37.15 |
| 2026-02-07 00:00 |
06:12:35.11 |
+54:58:15.8 |
HIP 29538 |
37.59 |
| 2026-02-07 12:00 |
06:12:31.05 |
+54:57:56.1 |
HIP 29085 |
37.88 |
| 2026-02-08 00:00 |
06:12:27.02 |
+54:57:36.1 |
HIP 29085 |
37.29 |
| 2026-02-08 12:00 |
06:12:23.04 |
+54:57:16.0 |
HIP 29085 |
36.69 |
| 2026-02-09 00:00 |
06:12:19.09 |
+54:56:55.8 |
HIP 29085 |
36.11 |
| 2026-02-09 12:00 |
06:12:15.19 |
+54:56:35.4 |
HIP 29085 |
35.54 |
| 2026-02-10 00:00 |
06:12:11.32 |
+54:56:14.8 |
HIP 29085 |
34.97 |
| 2026-02-10 12:00 |
06:12:07.50 |
+54:55:54.0 |
HIP 29085 |
34.41 |
| 2026-02-11 00:00 |
06:12:03.71 |
+54:55:33.2 |
HIP 29085 |
33.86 |
| 2026-02-11 12:00 |
06:11:59.96 |
+54:55:12.1 |
HIP 29085 |
33.32 |
| 2026-02-12 00:00 |
06:11:56.26 |
+54:54:50.9 |
HIP 29085 |
32.79 |
| 2026-02-12 12:00 |
06:11:52.60 |
+54:54:29.6 |
HIP 29085 |
32.27 |
| 2026-02-13 00:00 |
06:11:48.97 |
+54:54:08.1 |
HIP 29085 |
31.76 |
| 2026-02-13 12:00 |
06:11:45.39 |
+54:53:46.4 |
HIP 29085 |
31.26 |
| 2026-02-14 00:00 |
06:11:41.86 |
+54:53:24.7 |
HIP 29085 |
30.77 |
| 2026-02-14 12:00 |
06:11:38.36 |
+54:53:02.7 |
HIP 29085 |
30.29 |
| 2026-02-15 00:00 |
06:11:34.91 |
+54:52:40.7 |
HIP 29085 |
29.82 |
| 2026-02-15 12:00 |
06:11:31.50 |
+54:52:18.5 |
HIP 29085 |
29.36 |
| 2026-02-16 00:00 |
06:11:28.13 |
+54:51:56.1 |
HIP 29085 |
28.92 |
| 2026-02-16 12:00 |
06:11:24.81 |
+54:51:33.6 |
HIP 29085 |
28.49 |
| 2026-02-17 00:00 |
06:11:21.53 |
+54:51:11.0 |
HIP 29085 |
28.07 |
| 2026-02-17 12:00 |
06:11:18.29 |
+54:50:48.3 |
HIP 29085 |
27.66 |
| 2026-02-18 00:00 |
06:11:15.10 |
+54:50:25.4 |
HIP 29085 |
27.27 |
| 2026-02-18 12:00 |
06:11:11.95 |
+54:50:02.4 |
HIP 29085 |
26.89 |
| 2026-02-19 00:00 |
06:11:08.85 |
+54:49:39.3 |
HIP 29085 |
26.53 |
| 2026-02-19 12:00 |
06:11:05.79 |
+54:49:16.1 |
HIP 29085 |
26.18 |
| 2026-02-20 00:00 |
06:11:02.77 |
+54:48:52.7 |
HIP 29085 |
25.85 |
| 2026-02-20 12:00 |
06:10:59.80 |
+54:48:29.3 |
HIP 29085 |
25.53 |
| 2026-02-21 00:00 |
06:10:56.88 |
+54:48:05.7 |
HIP 29085 |
25.23 |
| 2026-02-21 12:00 |
06:10:54.00 |
+54:47:42.0 |
HIP 29085 |
24.94 |
| 2026-02-22 00:00 |
06:10:51.17 |
+54:47:18.2 |
HIP 29085 |
24.68 |
| 2026-02-22 12:00 |
06:10:48.38 |
+54:46:54.2 |
HIP 29085 |
24.42 |
| 2026-02-23 00:00 |
06:10:45.64 |
+54:46:30.2 |
HIP 29085 |
24.19 |
| 2026-02-23 12:00 |
06:10:42.95 |
+54:46:06.1 |
HIP 29085 |
23.97 |
| 2026-02-24 00:00 |
06:10:40.30 |
+54:45:41.8 |
HIP 29085 |
23.77 |