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Cloudy Skies and Comet NEOWISE

Posted: 27 July 2020

Tuesday, 21 July 2020, was cloudy. Early Wednesday morning, 22 July, had some light rain (0.04") and then another brief thundershower in the afternoon (0.07"). Thursday, 23 July, had more rain during the day (0.11"). As a result of rain on Mt Lemmon the Bighorn Fire was finally fully contained after burning 119,978 acres. About an hour before sunset this bobcat was relaxing outside my room.

Click or tap on image for larger version

Friday morning, 24 July, we saw the bobcat again but it was limping, not wanting to put any weight on its left paw.

Friday there were some periods of light rain (total 0.01"). The overcast nights prevented any viewing of Comet C/2020 F3 NEOWISE. Cloudy skies continued until Sunday, 26 July, which dawned clear, but with a cloudy night forecast. Clouds from Monsoon moisture began appearing mid-morning due to solar heating and the forecast for the night changed to mostly clear.

When I was a Meteorology Graduate Student I learned about the "Consistency Forecasting Theory"; whatever the weather was doing now, forecast it to continue. If raining, forecast rain. If clear, forecast a clear sky. Of course, there are many factors that are included in making weather forecasts. Which forecast would be correct for Sunday night? As it turned out, the sky was mostly clear as sunset approached, but it did not stay that way.

Open: Sunday, 26 July 2020, 1921 MST
Temperature: 97°F
Session: 1502
Conditions: Mostly clear

12" f/8 LX600 w/StarLock
2" 24mm UWA eyepiece
2" 5.5mm 100° eyepiece

iPhone 11 Pro Max

When I arrived at the observatory a very dramatic cumulonimbus cloud from a Monsoon storm was visible in the east.


1930 MST: sunset.

1935 MST: LX600 ON, StarLock OFF, High Precision OFF.

SYNCed the observatory clock to WWV time signals.

Viewed the Moon, 102X.

Took this handheld iPhone 11 Pro Max afocal 102X photo of the Moon using the iOS app NightCap Camera (ISO 32, 1/1250sec, 1X lens).


Did some lunar viewing using the Explore Scientific 2" 5.5mm 100° eyepiece (443X). The views were very impressive.

Took this handheld iPhone 11 Pro Max afocal 443X photo showing the craters Aristotelese and Eudoxus using the iOS app NightCap Camera (ISO 640, 1/60sec, 1X lens).


I then began searching the western sky for Comet C/2020 F3 NEOWISE. 2009 MST: sighted the comet using 12x50 binoculars. Only the head was visible; no visible tail. The comet was not visible to the naked eye due to the brightness of the twilight sky.

2013 MST: clouds were approaching the comet! I began preparing to photograph the comet using the D850 DSLR with a 70-300mm lens. By the time I was ready to begin photographing Comet NEOWISE the clouds had reached the comet. Here some photographs of Comet C/2020 F3 NEOWISE and the moonlit clouds. The comet is located near the center of each photograph.

2023 MST: f/4.5, 4 seconds, ISO 5000, FL 70mm; a short tail is faintly visible straight up

2031 MST: f/4.5, 2 seconds, ISO 6400, FL 70mm

2033 MST: f/5.6, 2 seconds, ISO 10000, FL 300mm

2035 MST: f/4.5, 1 second, ISO 12800, FL 70mm

2037 MST: the sky was now mostly cloudy. The comet was totally obscured. Ended photography and began preparing to close the observatory. A disappointing session with Comet NEOWISE.

2040 MST: LX600 OFF.

Close: Sunday, 26 July 2020, 2050 MST
Temperature: 85°F
Session Length: 1h 29m
Conditions: Mostly cloudy

I have submitted my reviews of the Explore Scientific 2" 9mm 120° eyepiece and Explore Scientific 2" 17mm and 12mm 92° eyepieces to Astronomy Technology Today. The reviews will be posted on my Cassiopeia Observatory site once they are published in the magazine.

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