254P/McNaught
Metadata
| Parameter | Value |
|---|---|
| Designation | 254P/McNaught |
| Type | P |
| Perihelion (tp_cal, UTC) | 2020-09-29T14:29:03.868800Z |
| Orbit solution date (soln_date, UTC) | 2026-03-07T14:43:32Z |
| Obs used | 834 |
| NEO | - |
| M1 | 12.900 |
| K1 | 4.500 |
| PC | - |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2020-08-07.0000000 |
| e | 0.32026893 |
| q (au) | 3.136948 |
| a (au) | 4.614984 |
| i (deg) | 32.571408 |
| Ω (om, deg) | 129.173330 |
| ω (w, deg) | 219.469297 |
| M (ma, deg) | 354.671045 |
Magnitude
Scatter + Global Linear
$$ M_a = (13.009 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 13.009 |
| n | 2.000 |
| gf | 1.000 |
| gb | -0.500 |
| 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 |
|---|---|---|---|
| 2020-10-03 | 2021-08-10 | -37.9052 | +20.265 |
| 2021-08-10 | 2025-03-31 | +10.0743 | -6.134 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Finding Chart
Ephemeris
| Date/Time (UTC) | RA (J2000) | Dec (J2000) | Nearest HIP | Dist from HIP (arcmin) |
|---|---|---|---|---|
| 2026-05-12 00:00 | 12:02:27.13 | +30:08:17.8 | HIP 58645 | 11.91 |
| 2026-05-12 12:00 | 12:02:20.84 | +30:07:25.2 | HIP 58645 | 10.65 |
| 2026-05-13 00:00 | 12:02:14.71 | +30:06:31.0 | HIP 58645 | 9.55 |
| 2026-05-13 12:00 | 12:02:08.75 | +30:05:35.4 | HIP 58645 | 8.66 |
| 2026-05-14 00:00 | 12:02:02.95 | +30:04:38.3 | HIP 58645 | 8.02 |
| 2026-05-14 12:00 | 12:01:57.31 | +30:03:39.8 | HIP 58645 | 7.70 |
| 2026-05-15 00:00 | 12:01:51.84 | +30:02:39.8 | HIP 58645 | 7.73 |
| 2026-05-15 12:00 | 12:01:46.53 | +30:01:38.4 | HIP 58645 | 8.09 |
| 2026-05-16 00:00 | 12:01:41.39 | +30:00:35.6 | HIP 58645 | 8.75 |
| 2026-05-16 12:00 | 12:01:36.42 | +29:59:31.4 | HIP 58645 | 9.64 |
| 2026-05-17 00:00 | 12:01:31.61 | +29:58:25.8 | HIP 58645 | 10.69 |
| 2026-05-17 12:00 | 12:01:26.97 | +29:57:18.9 | HIP 58645 | 11.86 |
| 2026-05-18 00:00 | 12:01:22.49 | +29:56:10.5 | HIP 58645 | 13.11 |
| 2026-05-18 12:00 | 12:01:18.19 | +29:55:00.8 | HIP 58645 | 14.43 |
| 2026-05-19 00:00 | 12:01:14.05 | +29:53:49.8 | HIP 58645 | 15.78 |
| 2026-05-19 12:00 | 12:01:10.08 | +29:52:37.4 | HIP 58645 | 17.17 |
| 2026-05-20 00:00 | 12:01:06.28 | +29:51:23.8 | HIP 58645 | 18.59 |
| 2026-05-20 12:00 | 12:01:02.65 | +29:50:08.8 | HIP 58658 | 19.43 |
| 2026-05-21 00:00 | 12:00:59.19 | +29:48:52.5 | HIP 58658 | 18.69 |
| 2026-05-21 12:00 | 12:00:55.89 | +29:47:35.0 | HIP 58658 | 18.01 |
| 2026-05-22 00:00 | 12:00:52.77 | +29:46:16.2 | HIP 58658 | 17.38 |
| 2026-05-22 12:00 | 12:00:49.81 | +29:44:56.2 | HIP 58658 | 16.82 |
| 2026-05-23 00:00 | 12:00:47.03 | +29:43:34.9 | HIP 58658 | 16.34 |
| 2026-05-23 12:00 | 12:00:44.41 | +29:42:12.4 | HIP 58658 | 15.94 |
| 2026-05-24 00:00 | 12:00:41.96 | +29:40:48.7 | HIP 58658 | 15.62 |
| 2026-05-24 12:00 | 12:00:39.68 | +29:39:23.8 | HIP 58658 | 15.41 |
| 2026-05-25 00:00 | 12:00:37.57 | +29:37:57.7 | HIP 58658 | 15.29 |
| 2026-05-25 12:00 | 12:00:35.63 | +29:36:30.4 | HIP 58658 | 15.29 |
| 2026-05-26 00:00 | 12:00:33.86 | +29:35:02.0 | HIP 58658 | 15.40 |
| 2026-05-26 12:00 | 12:00:32.26 | +29:33:32.4 | HIP 58658 | 15.61 |
| 2026-05-27 00:00 | 12:00:30.82 | +29:32:01.7 | HIP 58658 | 15.94 |
| 2026-05-27 12:00 | 12:00:29.55 | +29:30:29.9 | HIP 58658 | 16.37 |
| 2026-05-28 00:00 | 12:00:28.45 | +29:28:56.9 | HIP 58658 | 16.90 |
| 2026-05-28 12:00 | 12:00:27.52 | +29:27:22.9 | HIP 58577 | 16.75 |
| 2026-05-29 00:00 | 12:00:26.76 | +29:25:47.7 | HIP 58577 | 15.28 |
| 2026-05-29 12:00 | 12:00:26.16 | +29:24:11.5 | HIP 58577 | 13.80 |
| 2026-05-30 00:00 | 12:00:25.73 | +29:22:34.2 | HIP 58577 | 12.33 |
| 2026-05-30 12:00 | 12:00:25.47 | +29:20:55.9 | HIP 58577 | 10.87 |
| 2026-05-31 00:00 | 12:00:25.37 | +29:19:16.5 | HIP 58577 | 9.43 |
| 2026-05-31 12:00 | 12:00:25.44 | +29:17:36.1 | HIP 58577 | 8.04 |
| 2026-06-01 00:00 | 12:00:25.68 | +29:15:54.7 | HIP 58577 | 6.75 |
| 2026-06-01 12:00 | 12:00:26.08 | +29:14:12.2 | HIP 58577 | 5.63 |
| 2026-06-02 00:00 | 12:00:26.65 | +29:12:28.8 | HIP 58577 | 4.82 |