171P/Spahr
| Parameter |
Value |
| Designation |
171P/Spahr |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2019-01-13T17:54:31.360320Z |
| Orbit solution date (soln_date, UTC) |
2026-01-13T22:29:44Z |
| Obs used |
654 |
| NEO |
- |
| M1 |
12.400 |
| K1 |
19.750 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2017-12-05.0000000 |
| e |
0.50195491 |
| q (au) |
1.771913 |
| a (au) |
3.557736 |
| i (deg) |
21.933855 |
| Ω (om, deg) |
101.703094 |
| ω (w, deg) |
347.168443 |
| M (ma, deg) |
300.553509 |
Magnitude
Scatter + Global Linear
$$
M_a = (13.485 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
13.485 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.500 |
| k |
1.000 |
| 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
Finding Chart
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
11:23:24.67 |
+34:18:39.9 |
HIP 55627 |
6.09 |
| 2026-02-03 12:00 |
11:23:13.71 |
+34:27:00.7 |
HIP 55627 |
14.16 |
| 2026-02-04 00:00 |
11:23:02.24 |
+34:35:18.5 |
HIP 55491 |
21.88 |
| 2026-02-04 12:00 |
11:22:50.24 |
+34:43:33.2 |
HIP 55491 |
14.55 |
| 2026-02-05 00:00 |
11:22:37.74 |
+34:51:44.7 |
HIP 55491 |
9.54 |
| 2026-02-05 12:00 |
11:22:24.73 |
+34:59:52.8 |
HIP 55546 |
3.58 |
| 2026-02-06 00:00 |
11:22:11.22 |
+35:07:57.4 |
HIP 55546 |
8.70 |
| 2026-02-06 12:00 |
11:21:57.22 |
+35:15:58.5 |
HIP 55506 |
4.57 |
| 2026-02-07 00:00 |
11:21:42.73 |
+35:23:55.8 |
HIP 55506 |
5.94 |
| 2026-02-07 12:00 |
11:21:27.77 |
+35:31:49.3 |
HIP 55462 |
6.92 |
| 2026-02-08 00:00 |
11:21:12.33 |
+35:39:38.8 |
HIP 55462 |
3.64 |
| 2026-02-08 12:00 |
11:20:56.43 |
+35:47:24.2 |
HIP 55462 |
10.99 |
| 2026-02-09 00:00 |
11:20:40.07 |
+35:55:05.4 |
HIP 55462 |
19.20 |
| 2026-02-09 12:00 |
11:20:23.26 |
+36:02:42.3 |
HIP 55251 |
19.52 |
| 2026-02-10 00:00 |
11:20:06.02 |
+36:10:14.8 |
HIP 55251 |
21.45 |
| 2026-02-10 12:00 |
11:19:48.34 |
+36:17:42.6 |
HIP 55281 |
13.40 |
| 2026-02-11 00:00 |
11:19:30.24 |
+36:25:05.9 |
HIP 55281 |
5.17 |
| 2026-02-11 12:00 |
11:19:11.73 |
+36:32:24.3 |
HIP 55281 |
3.05 |
| 2026-02-12 00:00 |
11:18:52.81 |
+36:39:37.8 |
HIP 55281 |
11.20 |
| 2026-02-12 12:00 |
11:18:33.49 |
+36:46:46.3 |
HIP 55191 |
9.50 |
| 2026-02-13 00:00 |
11:18:13.80 |
+36:53:49.7 |
HIP 55191 |
2.84 |
| 2026-02-13 12:00 |
11:17:53.72 |
+37:00:47.8 |
HIP 55191 |
7.44 |
| 2026-02-14 00:00 |
11:17:33.28 |
+37:07:40.6 |
HIP 55191 |
15.17 |
| 2026-02-14 12:00 |
11:17:12.49 |
+37:14:28.0 |
HIP 55089 |
10.74 |
| 2026-02-15 00:00 |
11:16:51.35 |
+37:21:09.9 |
HIP 55089 |
2.83 |
| 2026-02-15 12:00 |
11:16:29.88 |
+37:27:46.1 |
HIP 55089 |
5.03 |
| 2026-02-16 00:00 |
11:16:08.09 |
+37:34:16.6 |
HIP 55030 |
4.91 |
| 2026-02-16 12:00 |
11:15:45.99 |
+37:40:41.2 |
HIP 55030 |
2.93 |
| 2026-02-17 00:00 |
11:15:23.59 |
+37:47:00.0 |
HIP 55030 |
10.61 |
| 2026-02-17 12:00 |
11:15:00.91 |
+37:53:12.7 |
HIP 55030 |
18.27 |
| 2026-02-18 00:00 |
11:14:37.95 |
+37:59:19.3 |
HIP 54941 |
25.10 |
| 2026-02-18 12:00 |
11:14:14.72 |
+38:05:19.8 |
HIP 54941 |
32.07 |
| 2026-02-19 00:00 |
11:13:51.25 |
+38:11:14.1 |
HIP 54941 |
39.17 |
| 2026-02-19 12:00 |
11:13:27.54 |
+38:17:02.0 |
HIP 55007 |
41.46 |
| 2026-02-20 00:00 |
11:13:03.61 |
+38:22:43.5 |
HIP 54591 |
36.45 |
| 2026-02-20 12:00 |
11:12:39.46 |
+38:28:18.6 |
HIP 54591 |
29.75 |
| 2026-02-21 00:00 |
11:12:15.12 |
+38:33:47.1 |
HIP 54591 |
23.43 |
| 2026-02-21 12:00 |
11:11:50.59 |
+38:39:09.1 |
HIP 54591 |
17.81 |
| 2026-02-22 00:00 |
11:11:25.88 |
+38:44:24.4 |
HIP 54591 |
13.70 |
| 2026-02-22 12:00 |
11:11:01.02 |
+38:49:33.0 |
HIP 54591 |
12.54 |
| 2026-02-23 00:00 |
11:10:36.01 |
+38:54:34.9 |
HIP 54591 |
14.96 |
| 2026-02-23 12:00 |
11:10:10.86 |
+38:59:30.0 |
HIP 54591 |
19.59 |
| 2026-02-24 00:00 |
11:09:45.59 |
+39:04:18.2 |
HIP 54579 |
20.40 |