155P/Shoemaker 2019-Dec-04 Charles Bell

155P/Shoemaker
2019-Dec-04 10:37:19 UTC
Exposure 864 secs R filter
Sky Motion 1.13"/min PA 100.6
ra 157.90586 dec +13.00510
Magnitude 16.47 +/- 0.05 R photAp 8.4 arcsec UCAC4
Coma 22 x 14 arcsec extended 292
Tail 7.1 arcmin PA 290
Charles Bell H47 Vicksburg
0.3-m Schmidt-Cassegrain + CCD + R filter
Field of View: 23.9' x 16.0'
ArcSinh() stretched with Fits Liberator
Annotated with Photoshop
Astrometry and Photometry with Astrometrica

JPL Horizons Ephemeris Data:
JD = 2458821.942581018
t - T = +19.29137 days
RA 157.90541 Dec 13.00538
Delta = 1.409 au
r = 1.814 au
Elong. = 96.9 deg
Phase = 32.6 deg
PsAng = 291.2 deg antisolar direction
PsAMV = 286.8 deg -v direction
PlAng = +1.9 deg orbit plane angle
True Anomaly = 10.3 deg
Constellation: Leo (Leo)

155P/Shoemaker was 19 days past perihelion.
The tail widens further from the head.
The orbit plane angle is low with both tail vectors near the same position angle and a phase angle of 33 degrees.
This gives an edge-on view of the coma and tail along orbit plane in which the tail and coma appear thicker.

155P is a Jupiter family comet with an orbital period of 16.9 years. The current orbit shows the object moving between 1.8 au at perihelion to beyond Saturn to 11.4 au at aphelion.
It passed about 1.4 au from Saturn in March 1962 and has several approaches to Jupiter near 1.0 to 1.3 au which have only mildy perturbed its orbit. Several similar future approaches to Saturn and Jupiter are calculated in the future through 2200.
155P has a Jupiter MOID of 0.30 au and at some point in the distant future may have a very close encounter with either Saturn or Jupiter.

155P was discovered on 1986 Jan. 10 at magnitude 12 by C. S. and E. M. Shoemaker at Palomar observatory using the 0.46-m Schmidt telescope.
This was their third comet discovery named for them. The comet had passed perihelion before discovery on 1985-Dec-18 at 1.794 au.
A peak brightness of magnitude 13.5 was reported in early Feb 1986 and then faded in the following months.

Observers T. Oribe and A. Nakamura from Japan recovered the comet in September 2002 near 18th magnitude at its next return.
Peak brightness was reported near magnitude 14.5 in Nov-2002. Perihelion occured on 2002-Dec-14 at 1.814 au.
The comet faded afterwards and was observed through May 2003 when it reached 18th to 19th magnitude.
Images taken of 155P in 2002 and 2003 can be found in the SkyMorph moving target archive.

155P was first observed during its 2019 return at magnitude 18.5 on 2019-Sep-05.
155P experienced a 1.1 magnitude outburst in October 2019.
Toshihiko Ikemura and Hirohisa Sato reported total magnitude of 15.4 on 2019-Nov-01.
155P passed perihelion on 2019-Nov-15 at 1.802 au.
155P is located currently in the eastern morning sky constellation of Leo and should be near 15th magnitude.
It stays in Leo until June 2020.

Earth passes through the comet orbit plane on 2019-Dec-29.
Near this time, the comet vectors PsAng and PsAMV will be 180 degrees from each other.
This observing geometry results in a tail pointing away from the sun nearest the head with a bends toward the opposite or negative velocity direction.
Earth passes closest to the comet on 2020-Feb-10 at 1.109 au when it peaks in brightness possibly near magnitude 14.5 and begins fading.