| Parameter |
Value |
| Designation |
C/1997 BA6 (Spacewatch) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1999-11-27T13:51:09.898560Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:50Z |
| Obs used |
520 |
| NEO |
- |
| M1 |
4.300 |
| K1 |
10.750 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2000-05-01.0000000 |
| e |
0.99888457 |
| q (au) |
3.436463 |
| a (au) |
3080.849437 |
| i (deg) |
72.717049 |
| Ω (om, deg) |
317.660522 |
| ω (w, deg) |
285.939608 |
| M (ma, deg) |
0.000896 |
Magnitude
Scatter + Global Linear
$$
M_a = (4.715 + 5.249\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
4.715 |
| n |
5.249 |
| gf |
1.000 |
| gb |
-0.692 |
| 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 |
| 1997-01-11 |
1998-11-25 |
+4.3922 |
-3.507 |
| 1998-11-25 |
1999-11-21 |
-2.6888 |
+1.565 |
| 1999-11-30 |
2002-09-12 |
-3.6083 |
+2.137 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-20 00:00 |
21:10:57.80 |
+59:57:43.7 |
HIP 104642 |
6.48 |
| 2026-09-20 12:00 |
21:10:54.26 |
+59:57:18.9 |
HIP 104642 |
7.01 |
| 2026-09-21 00:00 |
21:10:50.75 |
+59:56:53.9 |
HIP 104642 |
7.55 |
| 2026-09-21 12:00 |
21:10:47.27 |
+59:56:28.7 |
HIP 104642 |
8.10 |
| 2026-09-22 00:00 |
21:10:43.82 |
+59:56:03.2 |
HIP 104642 |
8.65 |
| 2026-09-22 12:00 |
21:10:40.40 |
+59:55:37.5 |
HIP 104642 |
9.21 |
| 2026-09-23 00:00 |
21:10:37.01 |
+59:55:11.6 |
HIP 104642 |
9.77 |
| 2026-09-23 12:00 |
21:10:33.65 |
+59:54:45.5 |
HIP 104642 |
10.34 |
| 2026-09-24 00:00 |
21:10:30.32 |
+59:54:19.2 |
HIP 104642 |
10.91 |
| 2026-09-24 12:00 |
21:10:27.02 |
+59:53:52.7 |
HIP 104642 |
11.48 |
| 2026-09-25 00:00 |
21:10:23.75 |
+59:53:26.0 |
HIP 104642 |
12.05 |
| 2026-09-25 12:00 |
21:10:20.51 |
+59:52:59.1 |
HIP 104642 |
12.62 |
| 2026-09-26 00:00 |
21:10:17.31 |
+59:52:32.0 |
HIP 104642 |
13.20 |
| 2026-09-26 12:00 |
21:10:14.14 |
+59:52:04.6 |
HIP 104642 |
13.77 |
| 2026-09-27 00:00 |
21:10:11.00 |
+59:51:37.1 |
HIP 104642 |
14.35 |
| 2026-09-27 12:00 |
21:10:07.89 |
+59:51:09.4 |
HIP 104642 |
14.92 |
| 2026-09-28 00:00 |
21:10:04.82 |
+59:50:41.5 |
HIP 104642 |
15.50 |
| 2026-09-28 12:00 |
21:10:01.77 |
+59:50:13.4 |
HIP 104515 |
15.34 |
| 2026-09-29 00:00 |
21:09:58.76 |
+59:49:45.1 |
HIP 104515 |
14.92 |
| 2026-09-29 12:00 |
21:09:55.79 |
+59:49:16.7 |
HIP 104515 |
14.51 |
| 2026-09-30 00:00 |
21:09:52.84 |
+59:48:48.0 |
HIP 104515 |
14.11 |
| 2026-09-30 12:00 |
21:09:49.94 |
+59:48:19.2 |
HIP 104515 |
13.71 |
| 2026-10-01 00:00 |
21:09:47.06 |
+59:47:50.2 |
HIP 104515 |
13.33 |
| 2026-10-01 12:00 |
21:09:44.22 |
+59:47:21.0 |
HIP 104515 |
12.97 |
| 2026-10-02 00:00 |
21:09:41.41 |
+59:46:51.7 |
HIP 104515 |
12.62 |
| 2026-10-02 12:00 |
21:09:38.64 |
+59:46:22.1 |
HIP 104515 |
12.28 |
| 2026-10-03 00:00 |
21:09:35.90 |
+59:45:52.4 |
HIP 104515 |
11.96 |
| 2026-10-03 12:00 |
21:09:33.20 |
+59:45:22.6 |
HIP 104515 |
11.66 |
| 2026-10-04 00:00 |
21:09:30.53 |
+59:44:52.5 |
HIP 104515 |
11.37 |
| 2026-10-04 12:00 |
21:09:27.90 |
+59:44:22.3 |
HIP 104515 |
11.11 |
| 2026-10-05 00:00 |
21:09:25.31 |
+59:43:52.0 |
HIP 104515 |
10.87 |
| 2026-10-05 12:00 |
21:09:22.75 |
+59:43:21.5 |
HIP 104515 |
10.66 |
| 2026-10-06 00:00 |
21:09:20.22 |
+59:42:50.8 |
HIP 104515 |
10.47 |
| 2026-10-06 12:00 |
21:09:17.73 |
+59:42:20.0 |
HIP 104515 |
10.31 |
| 2026-10-07 00:00 |
21:09:15.28 |
+59:41:49.0 |
HIP 104515 |
10.17 |
| 2026-10-07 12:00 |
21:09:12.87 |
+59:41:17.9 |
HIP 104515 |
10.07 |
| 2026-10-08 00:00 |
21:09:10.49 |
+59:40:46.6 |
HIP 104515 |
9.99 |
| 2026-10-08 12:00 |
21:09:08.15 |
+59:40:15.2 |
HIP 104515 |
9.94 |
| 2026-10-09 00:00 |
21:09:05.85 |
+59:39:43.7 |
HIP 104515 |
9.93 |
| 2026-10-09 12:00 |
21:09:03.58 |
+59:39:12.0 |
HIP 104515 |
9.95 |
| 2026-10-10 00:00 |
21:09:01.35 |
+59:38:40.2 |
HIP 104515 |
10.00 |
| 2026-10-10 12:00 |
21:08:59.16 |
+59:38:08.2 |
HIP 104515 |
10.08 |
| 2026-10-11 00:00 |
21:08:57.01 |
+59:37:36.2 |
HIP 104515 |
10.19 |