Comet C/2018 Y1 (Iwamoto) Moves Across the Winter Sky

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.

Comet C/2018 Y1 (Iwamoto).
Comet C/2018 Y1 (Iwamoto).

From Universe Today:

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.

A one-hour composite of C/2018 Y1 (Iwamoto) showing the rapid motion of the comet.
A one-hour composite of C/2018 Y1 (Iwamoto) showing the rapid motion of the comet.

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.

Comet C/2018 V1 (Machholz-Fujikawa-Iwamoto) in the Morning Sky

Venus and Spica in the morning twilight.
Venus and Spica in the morning twilight.

There’s a new comet in the morning sky. The comet was discovered in early November by three amateur astronomers—one in Arizona and two in Japan. Nowadays, most comets and asteroids are discovered by robotic Near-Earth-Object (NEO) search programs. The discovery of a comet by amateur astronomers is becoming a rare event.

So, with that bit of information, I set out to capture some images of the comet. As an 8th magnitude object it would not be easy using a short telephoto (i.e., 85mm focal length). My first attempt was marred by clouds but after viewing the images later I was finally able to find the small and not very bright comet.

A few days later I tried again. And, once again, high clouds moved across the sky. Finally, just before twilight, the clouds moved out of the way and I was able to get about 25 minutes of images.


Because the comet is so dim, individual images are not very revealing. In this case, better results are obtained by creating a short animation over the 25 minutes showing the motion of the comet relative to the stars.

As the eastern sky brightened the planet Venus and nearby star Spica stood out (image at top of post). A very nice end to a morning of shooting photographs in the cold.