| Parameter |
Value |
| Designation |
26P/Grigg-Skjellerup |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2013-07-06T00:05:12.914880Z |
| Orbit solution date (soln_date, UTC) |
2024-10-11T15:43:03Z |
| Obs used |
511 |
| NEO |
Yes |
| M1 |
16.500 |
| K1 |
5.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2012-03-31.0000000 |
| e |
0.63966796 |
| q (au) |
1.089725 |
| a (au) |
3.024224 |
| i (deg) |
22.455114 |
| Ω (om, deg) |
211.633966 |
| ω (w, deg) |
1.896086 |
| M (ma, deg) |
273.417838 |
Magnitude
Scatter + Global Linear
$$
M_a = (13.785 + 4.946\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
13.785 |
| n |
4.946 |
| gf |
0.975 |
| gb |
-0.927 |
| k |
0.996 |
| δ90 |
1.000 |
| 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
Finding Chart
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-07-29 00:00 |
02:49:48.43 |
+15:40:04.1 |
HIP 13258 |
11.90 |
| 2026-07-29 12:00 |
02:49:58.41 |
+15:40:06.4 |
HIP 13258 |
9.56 |
| 2026-07-30 00:00 |
02:50:08.23 |
+15:40:07.9 |
HIP 13258 |
7.30 |
| 2026-07-30 12:00 |
02:50:17.88 |
+15:40:08.5 |
HIP 13258 |
5.18 |
| 2026-07-31 00:00 |
02:50:27.38 |
+15:40:08.3 |
HIP 13258 |
3.37 |
| 2026-07-31 12:00 |
02:50:36.71 |
+15:40:07.1 |
HIP 13258 |
2.53 |
| 2026-08-01 00:00 |
02:50:45.88 |
+15:40:05.1 |
HIP 13258 |
3.39 |
| 2026-08-01 12:00 |
02:50:54.88 |
+15:40:02.1 |
HIP 13258 |
5.10 |
| 2026-08-02 00:00 |
02:51:03.72 |
+15:39:58.3 |
HIP 13258 |
7.04 |
| 2026-08-02 12:00 |
02:51:12.39 |
+15:39:53.6 |
HIP 13258 |
9.03 |
| 2026-08-03 00:00 |
02:51:20.89 |
+15:39:47.9 |
HIP 13258 |
11.02 |
| 2026-08-03 12:00 |
02:51:29.23 |
+15:39:41.4 |
HIP 13258 |
12.99 |
| 2026-08-04 00:00 |
02:51:37.39 |
+15:39:33.9 |
HIP 13258 |
14.93 |
| 2026-08-04 12:00 |
02:51:45.38 |
+15:39:25.6 |
HIP 13258 |
16.85 |
| 2026-08-05 00:00 |
02:51:53.21 |
+15:39:16.3 |
HIP 13258 |
18.73 |
| 2026-08-05 12:00 |
02:52:00.85 |
+15:39:06.0 |
HIP 13258 |
20.57 |
| 2026-08-06 00:00 |
02:52:08.33 |
+15:38:54.9 |
HIP 13258 |
22.37 |
| 2026-08-06 12:00 |
02:52:15.63 |
+15:38:42.8 |
HIP 13258 |
24.14 |
| 2026-08-07 00:00 |
02:52:22.75 |
+15:38:29.8 |
HIP 13258 |
25.87 |
| 2026-08-07 12:00 |
02:52:29.69 |
+15:38:15.9 |
HIP 13533 |
27.42 |
| 2026-08-08 00:00 |
02:52:36.46 |
+15:38:01.0 |
HIP 13533 |
25.80 |
| 2026-08-08 12:00 |
02:52:43.05 |
+15:37:45.1 |
HIP 13533 |
24.21 |
| 2026-08-09 00:00 |
02:52:49.45 |
+15:37:28.3 |
HIP 13533 |
22.66 |
| 2026-08-09 12:00 |
02:52:55.67 |
+15:37:10.6 |
HIP 13533 |
21.16 |
| 2026-08-10 00:00 |
02:53:01.71 |
+15:36:51.8 |
HIP 13533 |
19.69 |
| 2026-08-10 12:00 |
02:53:07.57 |
+15:36:32.1 |
HIP 13533 |
18.25 |
| 2026-08-11 00:00 |
02:53:13.24 |
+15:36:11.5 |
HIP 13533 |
16.86 |
| 2026-08-11 12:00 |
02:53:18.73 |
+15:35:49.9 |
HIP 13533 |
15.50 |
| 2026-08-12 00:00 |
02:53:24.02 |
+15:35:27.3 |
HIP 13533 |
14.18 |
| 2026-08-12 12:00 |
02:53:29.13 |
+15:35:03.7 |
HIP 13533 |
12.90 |
| 2026-08-13 00:00 |
02:53:34.06 |
+15:34:39.1 |
HIP 13533 |
11.65 |
| 2026-08-13 12:00 |
02:53:38.79 |
+15:34:13.6 |
HIP 13533 |
10.44 |
| 2026-08-14 00:00 |
02:53:43.33 |
+15:33:47.0 |
HIP 13533 |
9.26 |
| 2026-08-14 12:00 |
02:53:47.68 |
+15:33:19.5 |
HIP 13533 |
8.12 |
| 2026-08-15 00:00 |
02:53:51.83 |
+15:32:51.0 |
HIP 13533 |
7.01 |
| 2026-08-15 12:00 |
02:53:55.80 |
+15:32:21.5 |
HIP 13533 |
5.94 |
| 2026-08-16 00:00 |
02:53:59.57 |
+15:31:51.0 |
HIP 13533 |
4.90 |
| 2026-08-16 12:00 |
02:54:03.15 |
+15:31:19.5 |
HIP 13533 |
3.89 |
| 2026-08-17 00:00 |
02:54:06.53 |
+15:30:47.0 |
HIP 13533 |
2.93 |
| 2026-08-17 12:00 |
02:54:09.71 |
+15:30:13.4 |
HIP 13533 |
2.03 |
| 2026-08-18 00:00 |
02:54:12.70 |
+15:29:38.9 |
HIP 13533 |
1.26 |
| 2026-08-18 12:00 |
02:54:15.49 |
+15:29:03.4 |
HIP 13533 |
0.89 |
| 2026-08-19 00:00 |
02:54:18.09 |
+15:28:26.8 |
HIP 13533 |
1.29 |