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Mars-Neptune Conjunction, Crescent Moon,
Asteroid Burkhead, Comet 46P/Wirtanen

Posted: 9 December 2018

Cloudy skies returned on Tuesday, 4 December 2018, and continued until Saturday, 8 December. Late Thursday afternoon, 6 December 2018, rain began (0.27") and continued on Friday, 7 December (0.13"). The cloudy nights meant that I missed observing the very close conjunction of the planets Mars and Neptune; 20' separation on Thursday, 6 December, and 18.5' on Friday, 7 December. Both planets would have easily fit into the field-of-view of my Explore Scientific 9mm (271X) 100° eyepiece on those nights.

Open: Saturday, 8 December 2018, 1735 MST
Temperature: 67°F
Session: 1313
Conditions: Mostly clear, high humidity

Equipment Used:
12" f/8 LX600 w/StarLock
2" 24mm UWA eyepiece
2" 50mm eyepiece
Focal Reducer


1845 MST: LX600 ON, StarLock OFF, High Precision OFF.

Viewed Mars, 102X. Seeing was very bad. Switched to the 2" 50mm eyepiece (49X) and viewed Mars and Neptune. They were 57' apart this evening and both did not quite fit into the field-of-view of the eyepiece (FOV 56' 40").

I then set up the D850 DSLR camera with the 150-600mm lens on a camera tripod (no tracking) on the observatory patio:


1805 MST: I took the following photograph of the Mars-Neptune conjunction (f/6.3, 1 second, ISO 3200, White Balance 4000K, Focal Length 600mm):

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1816 MST: I switched to the 24-70mm lens and took this cropped photo of the thin crescent Moon and Earthshine with Saturn to its left (f/2.8, 2 seconds, ISO 1600, White Balance 4000K, Focal Length 70mm):


1821 MST: returned to the 12" telescope and viewed Neptune, 102X.

1823 MST: Stella Wi-Fi Adapter ON.

Used SkySafari 6 Pro to GOTO Asteroid (9143) Burkhead. This asteroid is named for one of my astronomy professors at Indiana University, 1966-1970. I had imaged this asteroid on the previous session but was unable to get a confirmation image that night due to poor seeing.

Mounted the D850 DSLR at prime focus + focal reducer, SYNCed on the star Algol, focused and locked the 12" primary mirror.

Prior to start of asteroid imaging I used the 12x50 binoculars to view the Mars-Neptune conjunction. It was not as impressive as it would have been on the two previous nights that were cloudy.

1840 MST: Wi-Fi OFF, StarLock ON.

Poor seeing (due to the high humidity) caused some StarLock autoguiding issues. I was finally able to acquire two StarLock autoguided images, 5 minutes, ISO 6400, WB 4000K at 1845 MST and 1945 MST. Here is Asteroid Burkhead (Mag. +16.5):


During the one hour interval between imaging the asteroid I located Comet 46P/Wirtanen with the naked eye. I confirmed it with the 12x50 binoculars. The comet was still faint with a large coma. No tail was visible in the binoculars.

1905 MST: while waiting to acquire the second image of Asteroid Burkhead I noticed that dew was heavy on the outside walls of the observatory. This high humidity rarely happens here when not raining.

1953 MST: Wi-Fi ON.

Used SkySafari to GOTO Comet 46P/Wirtanen. 1955 MST: Wi-Fi OFF.

Took this image of the comet, StarLock autoguided, prime focus + focal reducer, 1 minute, ISO 6400, WB 4000K:


A short tail is visible at the 11 o'clock position.

2006 MST: StarLock OFF.

I was surprised that the comet's coma was not larger in the image. I then noticed that the telescope corrector plate was totally covered by dew! I had been checking the plate throughout the evening but I don't know when the dew formed. That wiped out any further imaging with the telescope.

Removed the camera and focal reducer. Viewed Comet 46P/Wirtanen, 102X, but the view was lousy due to the dew-covered corrector plate.

2013 MST: LX600 OFF.

The humidity was 73%. My logbook paper was wet. Egads.

I mounted the D850 DSLR on the camera tripod and did some imaging of Comet 46P/Wirtanen with the 24-70mm lens. 2039 MST: Pleiades, Hyades, and the Comet, f/2.8, 15 seconds, ISO 6400, WB 4000K, FL 46mm:


Close: Saturday, 8 December 2018, 2048 MST
Temperature: 47°F
Session Length: 3h 13m
Conditions: Clear, humidity 75%

After I left the observatory I set up the D850 DSLR on the house front patio for an attempt to photograph the launch of a United Launch Alliance Delta IV-Heavy rocket from Vandenberg AFB, California, at 2115 MST. I suspected that I would not see the launch due to the muck along the western horizon. The launch was aborted at T minus 7 seconds. So the only launch from Vandenberg that I've been able to photograph from Oracle, Arizona, was a SpaceX Falcon 9 on 22 December 2017.

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