Dr. Roy Spencer writes on Facebook:
We finally got some dry air in N. Alabama, so I captured ~900 photos of comet NEOWISE starting about 3:45 this morning from the Monte Sano east overlook, using 2 cameras, one wide angle (30mm) for landscape shots and one telephoto (200 mm) for time lapse.
Time lapse video I took of Comet NEOWISE this morning from Huntsville, AL (watch full-screen). I used constant camera exposure settings, so you can see how much the sky brightens in only 20 minutes.
Comet NEOWISE rising in the northeast sky from Huntsville, AL, on July 11, 2020. Constant camera settings (2.5 sec exp., ISO 640, f/2.8) with a Canon 6D MkII, and Canon 200 mm lens.
The comet arrived at perihelion on July 3, sweeping to within 27.7 million miles (44.5 million km) of the sun and is now heading back out to the outer reaches of space. Nonetheless, the comet continues to evolve and its tail continues to grow.
Until now, the comet has been accessible only to those waking up at the break of dawn and scanning the sky near the northeast horizon. The comet has appeared to rise tail-first, followed by its bright head or coma, shining as bright as a first-magnitude star. So far, the comet has had to compete with low altitude, bright twilight and the light of a nearly-full moon. Some have been stymied from getting a good look at NEOWISE because of these factors, or perhaps because of poor weather. But things are going to be getting better for skywatchers in the days ahead.
Although the comet is moving away from the sun and beginning to fade, that dimming initially will likely be slow, because it is now approaching the Earth. It will be closest to our planet on the evening of July 22 (“perigee”), when it will be 64.3 million miles (103.5 million km) away. Thereafter, fading will be more rapid as the comet will then be receding from both the Earth and the sun.
As a morning object, the comet’s best views will come during a three-day stretch on the mornings of July 11, 12 and 13, when it will stand 10 degrees above the northeast horizon, 80 minutes before sunrise — the beginning of nautical twilight. Your clenched fist held at arm’s length measures approximately 10 degrees in width. So, on these three mornings, the head of Comet NEOWISE will appear about “one fist” up from the northeast horizon.
The sky should appear reasonably dark at that time with only the light of the last quarter moon providing any interference. As the minutes tick off, the comet will be getting higher, but the dawn sky will be getting increasingly brighter as well.
After July 13, NEOWISE will drop rapidly lower and swing more toward the north-northeast. By July 18, it will appear only 5 degrees above the horizon at the start of nautical twilight. And only a few mornings later its altitude will have become too low to see it at all in pre-sunrise sky.
But as its morning visibility diminishes, there is good news: Comet NEOWISE will become prominent in the evening sky after sunset. That will also mean a much larger audience will be able to see it during “prime-time” viewing hours instead of having to awaken during the wee hours of the early morning.
The first good opportunity for evening viewing begins on July 12, when the head of the comet will stand 5 degrees above the north-northwest horizon, 80 minutes after sunset (the end of nautical twilight). By July 14 its altitude will have already doubled to 10 degrees, and by July 19 it will have doubled yet again to 20 degrees up by the end of nautical twilight. By then it will have moved to above the northwest horizon.
So, we at Space.com feel that the best time to view the comet during the evening will come during the July 14-19 time frame.
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