Cassiopeia Observatory logo

Asteroid Wrubel, Comet Wirtanen

Posted: 1 November 2018

Saturday, 27 October 2018, was clear. That evening I attended a star party at Oracle State Park, our local IDA "International Dark Sky Park". My report of the successful event is on the ODSC web site.

Sunday, 28 October, dawned clear but clouds began arriving mid-morning, with the sky mostly cloudy by sunset. Cloudy skies continued until Tuesday afternoon, 30 October, when some partial clearing began. Unfortunately strong winds accompanied the slowly clearing skies. Wednesday, 31 October, was partly cloudy during the daytime but mostly clear by sunset.

Open: Wednesday, 31 October 2018, 1809 MST
Temperature: 71°F
Session: 1295
Conditions: Mostly clear

Equipment Used:
12" f/8 LX600 w/StarLock
2" 24mm UWA eyepiece
Focal Reducer


1814 MST: LX600 ON, StarLock OFF, High Precision OFF.

1816 MST: viewed Jupiter, 102X. Only one moon was visible. Then viewed Mercury, 102X. Both planets were very low in the southwestern sky. Mercury looked like a flashing beacon, rapidly changing from white to red, green, blue, and back to white due to atmospheric refraction.

Next, viewed Saturn and four moons, 102X. Mars showed a nice gibbous phase with the South Polar Cap and a large dark surface area visible.

Slewed to the star Fomalhaut and SYNCed the AutoStar on it.

1836 MST: High Precision ON. Viewed M74 (galaxy), very low in the eastern sky, 102X. The galaxy was faintly visible against a still bright twilight sky. 1837 MST: High Precision OFF.

Prepared the D850 DSLR for imaging.

1900 MST: Stella Wi-Fi Adapter ON. Used SkySafari 6 Pro on the iPhone to GOTO Asteroid (1765) Wrubel (Mag. +14.2). The asteroid was still behind a tree. This asteroid is named for Dr. Marshal H. Wrubel, who was a professor at Indiana University when I was an astrophysics undergraduate student there. I took one class from him: Galactic Structures, which was a graduate level class.

1904 MST: Wi-Fi OFF.

1930 MST: Asteroid Wrubel had cleared the tree. Began waiting for it to rise a little higher.

1945 MST: mounted the D850 DSLR at prime focus + focal reducer, focused on the star Fomalhaut, and locked the 12" primary mirror. Wi-Fi ON. Used SkySafari to GOTO Asteroid Wrubel. 1957 MST: StarLock ON.

Took images of Asteroid (1765) Wrubel at 2000 MST and 2100 MST, StarLock autoguided, 5 minute exposures, ISO 6400, White Balance 4000K. This is the first of those images (cropped):


This is a merge of the two images showing the movement of Asteroid Wrubel over the one hour interval:


After taking the second image of Asteroid Wrubel, used SkySafari to GOTO Comet 46P/Wirtanen (currently Mag. +7.3). It may become a naked eye comet in December. After doing some framing test exposures, took this (cropped) StarLock autoguided, 3 minute exposure, ISO 6400, WB 4000K, image of Comet Wirtanen:


2130 MST: StarLock OFF, Wi-Fi OFF.

2141 MST: viewed Comet Wirtanen, 102X. It was not very impressive visually. Only a faint coma was visible, with no tail visible.

2144 MST: LX600 OFF.

Close: Wednesday, 31 October 2018, 2156 MST
Temperature: 51°F
Session Length: 3h 47m
Conditions: Clear

My friend and former Indiana University college roommate John Martellaro has interviewed Indiana University Astronomer Dr. Catherine Pilachowski for his weekly podcast. To learn about getting started on a career in astronomy and some fascinating research, have a listen at

Comments are welcome using Email. Twitter users can use the button below to tweet this report to their followers. Thanks.

Previous report

Cassiopeia Observatory Home Page

Back to Top

Copyright ©2018 Michael L. Weasner /