| Parameter |
Value |
| Designation |
C/2021 C3 (Catalina) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2021-02-12T10:38:30.753600Z |
| Orbit solution date (soln_date, UTC) |
2024-06-21T13:42:16Z |
| Obs used |
363 |
| NEO |
- |
| M1 |
16.100 |
| K1 |
4.500 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2021-02-07T11:02:01.017600Z |
| Discovery magnitude (MPC) |
19.15 G |
| Discovery observatory (MPC) |
703 · University of Arizona Catalina Sky Survey |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2021-03-28.0000000 |
| e |
0.96405640 |
| q (au) |
2.276500 |
| a (au) |
63.335351 |
| i (deg) |
122.161615 |
| Ω (om, deg) |
181.919832 |
| ω (w, deg) |
357.151666 |
| M (ma, deg) |
0.085170 |
Magnitude
Scatter + Global Linear
$$
M_a = (17.520 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
17.520 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-0.650 |
| k |
0.800 |
| 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
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) |
End (UTC) |
a |
b |
| 2021-02-13 |
2021-06-09 |
-16.5522 |
+5.942 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-06-01 00:00 |
01:01:28.12 |
+46:19:36.5 |
HIP 4734 |
11.81 |
| 2026-06-01 12:00 |
01:01:33.61 |
+46:20:39.7 |
HIP 4734 |
13.22 |
| 2026-06-02 00:00 |
01:01:39.03 |
+46:21:42.9 |
HIP 4734 |
14.63 |
| 2026-06-02 12:00 |
01:01:44.39 |
+46:22:46.3 |
HIP 4734 |
16.03 |
| 2026-06-03 00:00 |
01:01:49.68 |
+46:23:49.8 |
HIP 4734 |
17.42 |
| 2026-06-03 12:00 |
01:01:54.90 |
+46:24:53.4 |
HIP 4734 |
18.81 |
| 2026-06-04 00:00 |
01:02:00.06 |
+46:25:57.2 |
HIP 4734 |
20.20 |
| 2026-06-04 12:00 |
01:02:05.15 |
+46:27:01.0 |
HIP 4734 |
21.57 |
| 2026-06-05 00:00 |
01:02:10.17 |
+46:28:04.9 |
HIP 4734 |
22.95 |
| 2026-06-05 12:00 |
01:02:15.12 |
+46:29:09.0 |
HIP 4734 |
24.31 |
| 2026-06-06 00:00 |
01:02:20.01 |
+46:30:13.1 |
HIP 4734 |
25.67 |
| 2026-06-06 12:00 |
01:02:24.82 |
+46:31:17.4 |
HIP 4734 |
27.03 |
| 2026-06-07 00:00 |
01:02:29.57 |
+46:32:21.7 |
HIP 4734 |
28.37 |
| 2026-06-07 12:00 |
01:02:34.24 |
+46:33:26.1 |
HIP 4900 |
29.59 |
| 2026-06-08 00:00 |
01:02:38.85 |
+46:34:30.6 |
HIP 4900 |
28.44 |
| 2026-06-08 12:00 |
01:02:43.38 |
+46:35:35.1 |
HIP 4900 |
27.31 |
| 2026-06-09 00:00 |
01:02:47.85 |
+46:36:39.7 |
HIP 4900 |
26.21 |
| 2026-06-09 12:00 |
01:02:52.24 |
+46:37:44.4 |
HIP 4900 |
25.12 |
| 2026-06-10 00:00 |
01:02:56.56 |
+46:38:49.2 |
HIP 4900 |
24.05 |
| 2026-06-10 12:00 |
01:03:00.80 |
+46:39:54.0 |
HIP 4900 |
23.00 |
| 2026-06-11 00:00 |
01:03:04.98 |
+46:40:58.8 |
HIP 4900 |
21.98 |
| 2026-06-11 12:00 |
01:03:09.08 |
+46:42:03.7 |
HIP 4900 |
20.99 |
| 2026-06-12 00:00 |
01:03:13.10 |
+46:43:08.7 |
HIP 4900 |
20.03 |
| 2026-06-12 12:00 |
01:03:17.05 |
+46:44:13.6 |
HIP 4900 |
19.10 |
| 2026-06-13 00:00 |
01:03:20.93 |
+46:45:18.6 |
HIP 4900 |
18.21 |
| 2026-06-13 12:00 |
01:03:24.73 |
+46:46:23.7 |
HIP 4900 |
17.36 |
| 2026-06-14 00:00 |
01:03:28.46 |
+46:47:28.7 |
HIP 4900 |
16.57 |
| 2026-06-14 12:00 |
01:03:32.11 |
+46:48:33.8 |
HIP 4900 |
15.82 |
| 2026-06-15 00:00 |
01:03:35.68 |
+46:49:38.9 |
HIP 4900 |
15.14 |
| 2026-06-15 12:00 |
01:03:39.17 |
+46:50:43.9 |
HIP 4900 |
14.52 |
| 2026-06-16 00:00 |
01:03:42.59 |
+46:51:49.0 |
HIP 4900 |
13.97 |
| 2026-06-16 12:00 |
01:03:45.93 |
+46:52:54.1 |
HIP 4900 |
13.51 |
| 2026-06-17 00:00 |
01:03:49.19 |
+46:53:59.2 |
HIP 4900 |
13.14 |
| 2026-06-17 12:00 |
01:03:52.37 |
+46:55:04.2 |
HIP 4900 |
12.86 |
| 2026-06-18 00:00 |
01:03:55.48 |
+46:56:09.2 |
HIP 4900 |
12.68 |
| 2026-06-18 12:00 |
01:03:58.50 |
+46:57:14.2 |
HIP 4900 |
12.60 |
| 2026-06-19 00:00 |
01:04:01.45 |
+46:58:19.2 |
HIP 4900 |
12.62 |
| 2026-06-19 12:00 |
01:04:04.31 |
+46:59:24.1 |
HIP 4900 |
12.74 |
| 2026-06-20 00:00 |
01:04:07.09 |
+47:00:29.0 |
HIP 4900 |
12.95 |
| 2026-06-20 12:00 |
01:04:09.80 |
+47:01:33.8 |
HIP 4900 |
13.25 |
| 2026-06-21 00:00 |
01:04:12.42 |
+47:02:38.6 |
HIP 4900 |
13.64 |
| 2026-06-21 12:00 |
01:04:14.96 |
+47:03:43.3 |
HIP 4900 |
14.09 |
| 2026-06-22 00:00 |
01:04:17.42 |
+47:04:47.9 |
HIP 4900 |
14.61 |