Comet C/2018 Y1 Iwamoto has just made its closest approach to Earth this week. With one evening of clear skies forecasted before the next storm system moves into the area, I went out earlier this week (02/11/2019) to capture images of this fast-moving, blue-green comet. The Moon was up in the western sky with 38% of the disk illuminated. This caused considerable brightening of the sky and made it challenging to capture fine details of the comet.
Discovered by Japanese amateur Masayuki Iwamoto as a +12th magnitude fuzzball moving through the constellation Hydra the Water Serpent on the night of December 18th, 2018, Y1 Iwamoto is a fast mover. It’s great to see that amateur astronomers can and still do discover comets, as the robotic competition posed by automated surveys such as PanSTARRS makes such an independent discovery tough these days…
At its closest on February 13th, Comet Y1 Iwamoto will appear to move seven degrees a day. This translates into a fast apparent motion of about 2/3rds the apparent diameter of a Full Moon, every hour.
The comet was easy to find with a pair of binoculars but was not visible to the unaided eye. Its position on this evening was near enough to the bright star Regulus that I had no trouble aligning the camera.
The following image and animation show the motion of the comet during a period of just over one hour.
Time lapse movie showing the motion of C/2018 Y1 during a period of one hour.
Comet C/2018 Y1 Iwamoto will make its next passage through the inner solar system in 3390 AD.
I have been looking forward to the recent Lunar eclipse (20 January 2019) since, well, the last one actually. During that eclipse, I shot images every three minutes while using an equatorial mount to track along with the stars. The results were good but there was some room for improvement. And that’s why I was looking forward to this event.
The weather had different plans for me. A stream of high-level tropical moisture was sitting right over Arizona all that day and most of the night. By late afternoon, the clouds were thick enough to partially obscure the sun. How was a darkened Moon going to shine through those clouds?
I could have just given up and stayed home but I was determined to at least try. I drove to Sedona to set up. Not because Sedona is a better place for viewing than Flagstaff but because Sedona is about 15 degrees warmer. And that matters.
I set up the tripod and then roughly aligned the iOptron Skytracker to where I made my best guess of the location of the star Polaris. Just as the umbral phase of the eclipse began, I was able to barely see Polaris through the thin clouds and completed the alignment of the tracker.
One of the things I learned last year was that three minutes was too large a time gap to make a smooth time-lapse video. My plan for this eclipse was to shoot at 1-minute intervals. But with the high clouds I realized that any time-lapse video was going to be challenging. So…3-minute intervals again. The clouds varied between fairly thick and mostly obscuring the moon to occasionally very thin allowing some lunar detail to be seen.
Here is a satellite image from GOES-16 showing the incredible stream of clouds moving across Arizona. I’m amazed that I got any photos at all!
Comet 46P/Wirtanen has already made its closest approach to both Earth and Sun and is now moving away. Yet it remains high in the sky making it an easy night-sky object if you are in a very dark location. It then appears as a full moon-sized smudge in the sky.
The full moon is now waning and rising later so that there are a few hours in which to observe the comet without the interference of moon light. We had one night without moon interference and without clouds so I took advantage.
Instead of taking multiple images and stacking I shot single images of 1, 2, and 3-minute exposure. Should have been easy. But there was a gusty wind blowing so that the camera and tripod was sometimes jostled resulting in streaky stars. And I had trouble focusing the telephoto lens I wanted to use (Nikon 70-300mm). Frustrated and cold, I grabbed my legacy zoom lens (Nikon 80-200mm AIS Manual Focus). This one is easy to focus on stars. Just rotate the focus ring all the way until it stops.
That’s the thing about some legacy manual focus lenses. They can be easier to focus than modern auto focus lenses in the dark so I keep several very old lenses around for that reason.
The past few nights have been interesting. On the evening of December 13–14 was the peak of the Geminid meteor shower. This year the expected peak was around 100–120 meteors per hour and various meteor counts appear to confirm that number.
At the same time, Comet 46P/Wirtanen has been getting a lot of attention. On December 16 it made its closest approach to Earth—only 11.5 million km away. That’s about 30 lunar distances for reference.
From SpaceWeather.com: “Although the comet is very close to Earth, it is not very bright. 46P/Wirtanen is a relatively small comet and, thus, barely visible to the unaided eye despite its proximity. It is nevertheless an easy target for digital cameras. Even a short exposure reveals the comet’s spherical form and emerald green hue.”
During the late evening of December 13, I traveled to Wupatki National Monument because of its dark skies. I shot a sequence of photos—each of 30 seconds duration—of the night sky hoping to catch a few meteors. One bright meteor blazed across the sky and I was able to catch part of it before it moved out of the frame of the camera. At the same time, the crescent Moon was setting in the west and gently illuminating Wukoki Pueblo. At the very top center of the photograph is Comet 46P/Wirtanen.
After about 1/2 hour of shooting meteors, I shot longer exposures of the comet. On this night, the comet formed a triangle with the Pleiades and Hyades star clusters. The image shown here is from ten 60-second images stacked using Deep Sky Stacker (DSS) and post-processed using rnc-color-stretch.
A few nights later, the comet had moved so that it was between the Pleiades and Hyades clusters. Again, I shot a sequence of 60-second exposures totaling about one hour in duration—this time from the Mormon Lake overlook. The motion of the comet is quite apparent in this sequence of images. The first image shows the motion of the comet against the stars; the second is a time-lapse movie of the same sequence.
Time lapse movie showing the motion of Comet 46P/Wirtanen during a period of one hour.
Comet 46P/Wirtanen is now moving farther from Earth and will slowly dim in brightness but it will remain visible through binoculors, telescopes, and with digital cameras for many weeks or more. There is still plenty of time to see the comet if you haven’t already.
I went out to the Mormon Lake Overlook early last evening (12/08/2018) to photograph a couple of different events. First was the launch of the ULA Delta IV-Heavy NROL-71 mission from Vandenburg Air Force Base. After that, I planned on pointing the camera up towards Comet 46P/Wirtanen.
Only part of my plans worked out. The launch was scrubbed at T-7 seconds but I didn’t know about that until much later. I just kept shooting a series of 15-seconds exposures pointed towards the western horizon and hoping that I would capture it. No launch—and there was nothing to capture.
But, wait, not so fast! It turns out there was a shallow layer of fog in the Mormon Lake basin and the series of 15-second exposures over a period of about 10 minutes resulted in a nice time-lapse movie of the fog. Unfortunately, the camera was pointed at mostly sky with very little of the ground but I’m happy with the lucky result.
Time lapse showing undulations on the top of the fog layer.
Next, I shot a series of 60-second exposures of the comet. Although the skies were cloudless, there was a lot of moisture in the air. See the discussion above about fog! The presence of this moisture and very thin fog above resulted in very colorful stars. A nice effect.
For the third act, I pointed the camera back down and over the lake basin towards Flagstaff. The fog was dissipating at this time but still shows up well. What also shows up is the large amount of light pollution in Flagstaff. Flagstaff is the worlds First International Dark Sky City but it takes a lot of work to keep the skies dark. I fear we may be losing the battle.