| Parameter |
Value |
| Designation |
C/2004 S1 (Van Ness) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2004-12-08T22:06:25.934400Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:30:43Z |
| Obs used |
122 |
| NEO |
- |
| M1 |
16.000 |
| K1 |
7.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2004-10-08.0000000 |
| e |
0.99999485 |
| q (au) |
0.681767 |
| a (au) |
132276.648552 |
| i (deg) |
114.666841 |
| Ω (om, deg) |
19.219692 |
| ω (w, deg) |
92.816645 |
| M (ma, deg) |
359.999999 |
Magnitude
Scatter + Global Linear
$$
M_a = (17.981 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
17.981 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-0.680 |
| k |
0.991 |
| δ90 |
10.000 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-05-12 00:00 |
07:40:29.86 |
-42:53:18.6 |
HIP 37424 |
18.47 |
| 2026-05-12 12:00 |
07:40:31.46 |
-42:52:47.1 |
HIP 37424 |
18.90 |
| 2026-05-13 00:00 |
07:40:33.08 |
-42:52:15.7 |
HIP 37424 |
19.33 |
| 2026-05-13 12:00 |
07:40:34.73 |
-42:51:44.5 |
HIP 37424 |
19.78 |
| 2026-05-14 00:00 |
07:40:36.41 |
-42:51:13.5 |
HIP 37424 |
20.22 |
| 2026-05-14 12:00 |
07:40:38.11 |
-42:50:42.7 |
HIP 37424 |
20.67 |
| 2026-05-15 00:00 |
07:40:39.84 |
-42:50:12.0 |
HIP 37424 |
21.12 |
| 2026-05-15 12:00 |
07:40:41.60 |
-42:49:41.6 |
HIP 37424 |
21.58 |
| 2026-05-16 00:00 |
07:40:43.38 |
-42:49:11.3 |
HIP 37424 |
22.04 |
| 2026-05-16 12:00 |
07:40:45.19 |
-42:48:41.3 |
HIP 37424 |
22.50 |
| 2026-05-17 00:00 |
07:40:47.02 |
-42:48:11.4 |
HIP 37424 |
22.96 |
| 2026-05-17 12:00 |
07:40:48.88 |
-42:47:41.7 |
HIP 37424 |
23.43 |
| 2026-05-18 00:00 |
07:40:50.77 |
-42:47:12.3 |
HIP 37424 |
23.90 |
| 2026-05-18 12:00 |
07:40:52.68 |
-42:46:43.0 |
HIP 37577 |
23.60 |
| 2026-05-19 00:00 |
07:40:54.61 |
-42:46:13.9 |
HIP 37577 |
23.04 |
| 2026-05-19 12:00 |
07:40:56.58 |
-42:45:45.1 |
HIP 37577 |
22.48 |
| 2026-05-20 00:00 |
07:40:58.56 |
-42:45:16.4 |
HIP 37577 |
21.92 |
| 2026-05-20 12:00 |
07:41:00.57 |
-42:44:48.0 |
HIP 37577 |
21.36 |
| 2026-05-21 00:00 |
07:41:02.60 |
-42:44:19.8 |
HIP 37577 |
20.81 |
| 2026-05-21 12:00 |
07:41:04.66 |
-42:43:51.8 |
HIP 37577 |
20.25 |
| 2026-05-22 00:00 |
07:41:06.74 |
-42:43:24.0 |
HIP 37577 |
19.69 |
| 2026-05-22 12:00 |
07:41:08.85 |
-42:42:56.4 |
HIP 37577 |
19.13 |
| 2026-05-23 00:00 |
07:41:10.98 |
-42:42:29.0 |
HIP 37577 |
18.58 |
| 2026-05-23 12:00 |
07:41:13.13 |
-42:42:01.9 |
HIP 37577 |
18.02 |
| 2026-05-24 00:00 |
07:41:15.30 |
-42:41:34.9 |
HIP 37577 |
17.47 |
| 2026-05-24 12:00 |
07:41:17.50 |
-42:41:08.2 |
HIP 37577 |
16.91 |
| 2026-05-25 00:00 |
07:41:19.72 |
-42:40:41.7 |
HIP 37577 |
16.36 |
| 2026-05-25 12:00 |
07:41:21.97 |
-42:40:15.5 |
HIP 37577 |
15.81 |
| 2026-05-26 00:00 |
07:41:24.23 |
-42:39:49.5 |
HIP 37577 |
15.25 |
| 2026-05-26 12:00 |
07:41:26.52 |
-42:39:23.7 |
HIP 37577 |
14.71 |
| 2026-05-27 00:00 |
07:41:28.83 |
-42:38:58.1 |
HIP 37577 |
14.16 |
| 2026-05-27 12:00 |
07:41:31.16 |
-42:38:32.8 |
HIP 37577 |
13.61 |
| 2026-05-28 00:00 |
07:41:33.52 |
-42:38:07.6 |
HIP 37577 |
13.07 |
| 2026-05-28 12:00 |
07:41:35.89 |
-42:37:42.8 |
HIP 37577 |
12.53 |
| 2026-05-29 00:00 |
07:41:38.29 |
-42:37:18.1 |
HIP 37577 |
11.99 |
| 2026-05-29 12:00 |
07:41:40.70 |
-42:36:53.7 |
HIP 37577 |
11.45 |
| 2026-05-30 00:00 |
07:41:43.14 |
-42:36:29.6 |
HIP 37577 |
10.92 |
| 2026-05-30 12:00 |
07:41:45.60 |
-42:36:05.6 |
HIP 37577 |
10.40 |
| 2026-05-31 00:00 |
07:41:48.08 |
-42:35:42.0 |
HIP 37577 |
9.88 |
| 2026-05-31 12:00 |
07:41:50.58 |
-42:35:18.5 |
HIP 37577 |
9.36 |
| 2026-06-01 00:00 |
07:41:53.10 |
-42:34:55.3 |
HIP 37577 |
8.86 |
| 2026-06-01 12:00 |
07:41:55.64 |
-42:34:32.4 |
HIP 37577 |
8.36 |
| 2026-06-02 00:00 |
07:41:58.20 |
-42:34:09.7 |
HIP 37577 |
7.88 |