| 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 |
0.997 |
| gb |
-0.500 |
| k |
0.800 |
| δ90 |
8.389 |
| 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) |
| 2026-03-26 00:00 |
06:09:28.59 |
+54:19:36.9 |
HIP 29491 |
36.53 |
| 2026-03-26 12:00 |
06:09:28.87 |
+54:19:10.2 |
HIP 29422 |
36.23 |
| 2026-03-27 00:00 |
06:09:29.19 |
+54:18:43.5 |
HIP 29422 |
35.84 |
| 2026-03-27 12:00 |
06:09:29.55 |
+54:18:16.9 |
HIP 29422 |
35.45 |
| 2026-03-28 00:00 |
06:09:29.97 |
+54:17:50.3 |
HIP 29422 |
35.07 |
| 2026-03-28 12:00 |
06:09:30.43 |
+54:17:23.7 |
HIP 29422 |
34.67 |
| 2026-03-29 00:00 |
06:09:30.94 |
+54:16:57.1 |
HIP 29422 |
34.28 |
| 2026-03-29 12:00 |
06:09:31.49 |
+54:16:30.6 |
HIP 29422 |
33.88 |
| 2026-03-30 00:00 |
06:09:32.10 |
+54:16:04.1 |
HIP 29422 |
33.48 |
| 2026-03-30 12:00 |
06:09:32.74 |
+54:15:37.7 |
HIP 29422 |
33.08 |
| 2026-03-31 00:00 |
06:09:33.44 |
+54:15:11.2 |
HIP 29422 |
32.68 |
| 2026-03-31 12:00 |
06:09:34.18 |
+54:14:44.8 |
HIP 29422 |
32.27 |
| 2026-04-01 00:00 |
06:09:34.96 |
+54:14:18.5 |
HIP 29422 |
31.86 |
| 2026-04-01 12:00 |
06:09:35.79 |
+54:13:52.2 |
HIP 29422 |
31.45 |
| 2026-04-02 00:00 |
06:09:36.67 |
+54:13:25.9 |
HIP 29422 |
31.04 |
| 2026-04-02 12:00 |
06:09:37.59 |
+54:12:59.7 |
HIP 29422 |
30.62 |
| 2026-04-03 00:00 |
06:09:38.56 |
+54:12:33.5 |
HIP 29422 |
30.20 |
| 2026-04-03 12:00 |
06:09:39.57 |
+54:12:07.3 |
HIP 29422 |
29.78 |
| 2026-04-04 00:00 |
06:09:40.63 |
+54:11:41.2 |
HIP 29422 |
29.35 |
| 2026-04-04 12:00 |
06:09:41.73 |
+54:11:15.2 |
HIP 29422 |
28.92 |
| 2026-04-05 00:00 |
06:09:42.88 |
+54:10:49.2 |
HIP 29422 |
28.49 |
| 2026-04-05 12:00 |
06:09:44.07 |
+54:10:23.3 |
HIP 29422 |
28.06 |
| 2026-04-06 00:00 |
06:09:45.30 |
+54:09:57.4 |
HIP 29422 |
27.62 |
| 2026-04-06 12:00 |
06:09:46.58 |
+54:09:31.5 |
HIP 29422 |
27.18 |
| 2026-04-07 00:00 |
06:09:47.91 |
+54:09:05.8 |
HIP 29422 |
26.74 |
| 2026-04-07 12:00 |
06:09:49.28 |
+54:08:40.0 |
HIP 29422 |
26.29 |
| 2026-04-08 00:00 |
06:09:50.69 |
+54:08:14.4 |
HIP 29422 |
25.84 |
| 2026-04-08 12:00 |
06:09:52.15 |
+54:07:48.8 |
HIP 29422 |
25.39 |
| 2026-04-09 00:00 |
06:09:53.65 |
+54:07:23.2 |
HIP 29422 |
24.94 |
| 2026-04-09 12:00 |
06:09:55.19 |
+54:06:57.8 |
HIP 29422 |
24.48 |
| 2026-04-10 00:00 |
06:09:56.78 |
+54:06:32.4 |
HIP 29422 |
24.02 |
| 2026-04-10 12:00 |
06:09:58.41 |
+54:06:07.0 |
HIP 29422 |
23.55 |
| 2026-04-11 00:00 |
06:10:00.08 |
+54:05:41.7 |
HIP 29422 |
23.09 |
| 2026-04-11 12:00 |
06:10:01.79 |
+54:05:16.5 |
HIP 29422 |
22.62 |
| 2026-04-12 00:00 |
06:10:03.55 |
+54:04:51.4 |
HIP 29422 |
22.15 |
| 2026-04-12 12:00 |
06:10:05.35 |
+54:04:26.4 |
HIP 29422 |
21.67 |
| 2026-04-13 00:00 |
06:10:07.20 |
+54:04:01.4 |
HIP 29422 |
21.19 |
| 2026-04-13 12:00 |
06:10:09.08 |
+54:03:36.5 |
HIP 29422 |
20.71 |
| 2026-04-14 00:00 |
06:10:11.01 |
+54:03:11.6 |
HIP 29422 |
20.23 |
| 2026-04-14 12:00 |
06:10:12.98 |
+54:02:46.9 |
HIP 29422 |
19.74 |
| 2026-04-15 00:00 |
06:10:14.99 |
+54:02:22.2 |
HIP 29422 |
19.25 |
| 2026-04-15 12:00 |
06:10:17.04 |
+54:01:57.6 |
HIP 29422 |
18.75 |
| 2026-04-16 00:00 |
06:10:19.13 |
+54:01:33.1 |
HIP 29422 |
18.26 |