| Parameter |
Value |
| Designation |
C/1967 Y1 (Ikeya-Seki) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1968-02-25T16:56:06.803520Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:17Z |
| Obs used |
197 |
| NEO |
- |
| M1 |
6.400 |
| K1 |
4.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1968-03-18.0000000 |
| e |
0.99915636 |
| q (au) |
1.696579 |
| a (au) |
2011.021687 |
| i (deg) |
129.315339 |
| Ω (om, deg) |
255.321380 |
| ω (w, deg) |
70.864407 |
| M (ma, deg) |
0.000233 |
Magnitude
Scatter + Global Linear
$$
M_a = (2.937 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
2.937 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-1.000 |
| 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 |
03:00:01.21 |
-23:30:40.9 |
HIP 13955 |
8.81 |
| 2026-05-12 12:00 |
03:00:02.66 |
-23:30:37.5 |
HIP 13955 |
8.93 |
| 2026-05-13 00:00 |
03:00:04.12 |
-23:30:34.2 |
HIP 13955 |
9.05 |
| 2026-05-13 12:00 |
03:00:05.57 |
-23:30:31.1 |
HIP 13955 |
9.19 |
| 2026-05-14 00:00 |
03:00:07.02 |
-23:30:28.1 |
HIP 13955 |
9.34 |
| 2026-05-14 12:00 |
03:00:08.47 |
-23:30:25.2 |
HIP 13955 |
9.50 |
| 2026-05-15 00:00 |
03:00:09.92 |
-23:30:22.4 |
HIP 13955 |
9.67 |
| 2026-05-15 12:00 |
03:00:11.37 |
-23:30:19.7 |
HIP 13955 |
9.85 |
| 2026-05-16 00:00 |
03:00:12.81 |
-23:30:17.2 |
HIP 13955 |
10.04 |
| 2026-05-16 12:00 |
03:00:14.26 |
-23:30:14.7 |
HIP 13955 |
10.24 |
| 2026-05-17 00:00 |
03:00:15.70 |
-23:30:12.4 |
HIP 13955 |
10.45 |
| 2026-05-17 12:00 |
03:00:17.15 |
-23:30:10.3 |
HIP 13955 |
10.66 |
| 2026-05-18 00:00 |
03:00:18.59 |
-23:30:08.2 |
HIP 13955 |
10.88 |
| 2026-05-18 12:00 |
03:00:20.02 |
-23:30:06.3 |
HIP 13955 |
11.11 |
| 2026-05-19 00:00 |
03:00:21.46 |
-23:30:04.4 |
HIP 13955 |
11.34 |
| 2026-05-19 12:00 |
03:00:22.89 |
-23:30:02.7 |
HIP 13955 |
11.58 |
| 2026-05-20 00:00 |
03:00:24.32 |
-23:30:01.2 |
HIP 13955 |
11.82 |
| 2026-05-20 12:00 |
03:00:25.75 |
-23:29:59.7 |
HIP 13955 |
12.07 |
| 2026-05-21 00:00 |
03:00:27.18 |
-23:29:58.4 |
HIP 13955 |
12.33 |
| 2026-05-21 12:00 |
03:00:28.60 |
-23:29:57.2 |
HIP 13955 |
12.58 |
| 2026-05-22 00:00 |
03:00:30.02 |
-23:29:56.1 |
HIP 13955 |
12.85 |
| 2026-05-22 12:00 |
03:00:31.44 |
-23:29:55.1 |
HIP 13955 |
13.11 |
| 2026-05-23 00:00 |
03:00:32.86 |
-23:29:54.3 |
HIP 13955 |
13.38 |
| 2026-05-23 12:00 |
03:00:34.27 |
-23:29:53.5 |
HIP 13955 |
13.65 |
| 2026-05-24 00:00 |
03:00:35.68 |
-23:29:52.9 |
HIP 13955 |
13.92 |
| 2026-05-24 12:00 |
03:00:37.08 |
-23:29:52.5 |
HIP 13955 |
14.20 |
| 2026-05-25 00:00 |
03:00:38.48 |
-23:29:52.1 |
HIP 13955 |
14.48 |
| 2026-05-25 12:00 |
03:00:39.88 |
-23:29:51.9 |
HIP 13955 |
14.76 |
| 2026-05-26 00:00 |
03:00:41.28 |
-23:29:51.8 |
HIP 13955 |
15.04 |
| 2026-05-26 12:00 |
03:00:42.67 |
-23:29:51.8 |
HIP 13955 |
15.32 |
| 2026-05-27 00:00 |
03:00:44.06 |
-23:29:51.9 |
HIP 13955 |
15.61 |
| 2026-05-27 12:00 |
03:00:45.44 |
-23:29:52.1 |
HIP 13955 |
15.89 |
| 2026-05-28 00:00 |
03:00:46.82 |
-23:29:52.5 |
HIP 13955 |
16.18 |
| 2026-05-28 12:00 |
03:00:48.20 |
-23:29:53.0 |
HIP 13955 |
16.47 |
| 2026-05-29 00:00 |
03:00:49.57 |
-23:29:53.6 |
HIP 13955 |
16.76 |
| 2026-05-29 12:00 |
03:00:50.94 |
-23:29:54.4 |
HIP 13955 |
17.05 |
| 2026-05-30 00:00 |
03:00:52.31 |
-23:29:55.2 |
HIP 13955 |
17.34 |
| 2026-05-30 12:00 |
03:00:53.67 |
-23:29:56.2 |
HIP 13955 |
17.64 |
| 2026-05-31 00:00 |
03:00:55.02 |
-23:29:57.3 |
HIP 13955 |
17.93 |
| 2026-05-31 12:00 |
03:00:56.37 |
-23:29:58.5 |
HIP 13955 |
18.22 |
| 2026-06-01 00:00 |
03:00:57.72 |
-23:29:59.8 |
HIP 13955 |
18.52 |
| 2026-06-01 12:00 |
03:00:59.06 |
-23:30:01.3 |
HIP 13955 |
18.81 |
| 2026-06-02 00:00 |
03:01:00.40 |
-23:30:02.9 |
HIP 13955 |
19.10 |