| Parameter |
Value |
| Designation |
27P/Crommelin |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2011-08-02T13:37:41.877120Z |
| Orbit solution date (soln_date, UTC) |
2023-05-12T09:58:07Z |
| Obs used |
455 |
| NEO |
Yes |
| M1 |
12.700 |
| K1 |
27.750 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2002-08-03.0000000 |
| e |
0.91925987 |
| q (au) |
0.734210 |
| a (au) |
9.093497 |
| i (deg) |
29.221115 |
| Ω (om, deg) |
250.959353 |
| ω (w, deg) |
195.955445 |
| M (ma, deg) |
241.872697 |
Magnitude
Scatter + Global Linear
$$
M_a = (15.302 + 5.211\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
15.302 |
| n |
5.211 |
| gf |
0.998 |
| gb |
-1.000 |
| k |
0.842 |
| δ90 |
9.969 |
| 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 |
| 2011-05-12 |
2011-07-25 |
+11.1741 |
-1.084 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-07-29 00:00 |
17:34:13.09 |
-14:29:23.3 |
HIP 86099 |
23.81 |
| 2026-07-29 12:00 |
17:34:08.22 |
-14:29:27.4 |
HIP 86099 |
24.88 |
| 2026-07-30 00:00 |
17:34:03.39 |
-14:29:31.6 |
HIP 85866 |
25.49 |
| 2026-07-30 12:00 |
17:33:58.61 |
-14:29:36.0 |
HIP 85866 |
24.63 |
| 2026-07-31 00:00 |
17:33:53.87 |
-14:29:40.4 |
HIP 85866 |
23.80 |
| 2026-07-31 12:00 |
17:33:49.18 |
-14:29:45.0 |
HIP 85866 |
23.01 |
| 2026-08-01 00:00 |
17:33:44.53 |
-14:29:49.7 |
HIP 85866 |
22.25 |
| 2026-08-01 12:00 |
17:33:39.92 |
-14:29:54.5 |
HIP 85866 |
21.53 |
| 2026-08-02 00:00 |
17:33:35.36 |
-14:29:59.4 |
HIP 85866 |
20.84 |
| 2026-08-02 12:00 |
17:33:30.85 |
-14:30:04.4 |
HIP 85866 |
20.20 |
| 2026-08-03 00:00 |
17:33:26.38 |
-14:30:09.6 |
HIP 85866 |
19.60 |
| 2026-08-03 12:00 |
17:33:21.96 |
-14:30:14.8 |
HIP 85866 |
19.05 |
| 2026-08-04 00:00 |
17:33:17.59 |
-14:30:20.2 |
HIP 85866 |
18.54 |
| 2026-08-04 12:00 |
17:33:13.27 |
-14:30:25.7 |
HIP 85866 |
18.09 |
| 2026-08-05 00:00 |
17:33:08.99 |
-14:30:31.2 |
HIP 85866 |
17.69 |
| 2026-08-05 12:00 |
17:33:04.76 |
-14:30:36.9 |
HIP 85866 |
17.34 |
| 2026-08-06 00:00 |
17:33:00.57 |
-14:30:42.8 |
HIP 85866 |
17.04 |
| 2026-08-06 12:00 |
17:32:56.44 |
-14:30:48.7 |
HIP 85866 |
16.81 |
| 2026-08-07 00:00 |
17:32:52.36 |
-14:30:54.7 |
HIP 85866 |
16.62 |
| 2026-08-07 12:00 |
17:32:48.32 |
-14:31:00.8 |
HIP 85866 |
16.50 |
| 2026-08-08 00:00 |
17:32:44.34 |
-14:31:07.1 |
HIP 85866 |
16.43 |
| 2026-08-08 12:00 |
17:32:40.40 |
-14:31:13.5 |
HIP 85866 |
16.41 |
| 2026-08-09 00:00 |
17:32:36.52 |
-14:31:19.9 |
HIP 85866 |
16.45 |
| 2026-08-09 12:00 |
17:32:32.68 |
-14:31:26.5 |
HIP 85866 |
16.53 |
| 2026-08-10 00:00 |
17:32:28.90 |
-14:31:33.2 |
HIP 85866 |
16.66 |
| 2026-08-10 12:00 |
17:32:25.17 |
-14:31:39.9 |
HIP 85866 |
16.84 |
| 2026-08-11 00:00 |
17:32:21.49 |
-14:31:46.8 |
HIP 85866 |
17.05 |
| 2026-08-11 12:00 |
17:32:17.86 |
-14:31:53.8 |
HIP 85866 |
17.31 |
| 2026-08-12 00:00 |
17:32:14.28 |
-14:32:00.9 |
HIP 85866 |
17.59 |
| 2026-08-12 12:00 |
17:32:10.76 |
-14:32:08.1 |
HIP 85866 |
17.91 |
| 2026-08-13 00:00 |
17:32:07.29 |
-14:32:15.4 |
HIP 85866 |
18.25 |
| 2026-08-13 12:00 |
17:32:03.87 |
-14:32:22.8 |
HIP 85866 |
18.62 |
| 2026-08-14 00:00 |
17:32:00.51 |
-14:32:30.3 |
HIP 85866 |
19.00 |
| 2026-08-14 12:00 |
17:31:57.20 |
-14:32:37.9 |
HIP 85866 |
19.41 |
| 2026-08-15 00:00 |
17:31:53.94 |
-14:32:45.6 |
HIP 85866 |
19.83 |
| 2026-08-15 12:00 |
17:31:50.74 |
-14:32:53.3 |
HIP 85866 |
20.26 |
| 2026-08-16 00:00 |
17:31:47.59 |
-14:33:01.2 |
HIP 85866 |
20.70 |
| 2026-08-16 12:00 |
17:31:44.50 |
-14:33:09.2 |
HIP 85866 |
21.15 |
| 2026-08-17 00:00 |
17:31:41.46 |
-14:33:17.3 |
HIP 85679 |
21.25 |
| 2026-08-17 12:00 |
17:31:38.47 |
-14:33:25.4 |
HIP 85679 |
20.60 |
| 2026-08-18 00:00 |
17:31:35.55 |
-14:33:33.7 |
HIP 85679 |
19.97 |
| 2026-08-18 12:00 |
17:31:32.67 |
-14:33:42.0 |
HIP 85679 |
19.35 |
| 2026-08-19 00:00 |
17:31:29.86 |
-14:33:50.5 |
HIP 85679 |
18.75 |