Seiichi Yoshida's Diary of Comet Observations (2017)

Japanese version
Home page
Updated on March 25, 2017

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Detailed observation data in ICQ format.

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* 2017 Mar. 22 (4 comets)

I observed 4 comets visually on Mar. 22 in Mt. Hanadate, Ibaraki, Japan.

I was lucky because this is the night of remarkable rendezvous between 41P and M97, M108.

C/2015 V2 ( Johnson )

9.5 mag   Dia. 5.5'   DC 5   (40.0-cm reflector 36x)

Now it is very bright.

41P/Tuttle-Giacobini-Kresak

8.3 mag   Dia. 10'   DC 3-4   (40.0-cm reflector 36x)

7.3 mag   Dia. 16'   DC 2   (10x70 monocular)

It is very nice that the comet looks in the same field of view with Owl Nebula M97 and galaxy M108. At that time the comet was closest to M108, and the coma was overlapping on the galaxy.

45P/Honda-Mrkos-Pajdusakova

13.6 mag   Dia. 1.0'   DC 0   (40.0-cm reflector 144x)

Now it becomes very faint. It was overlapping on a 14-mag star at first, so I waited for some time. But maybe my observation was influenced by the star.

315P/LONEOS

14.0 mag   Dia. 0.5'   DC 2   (40.0-cm reflector 257x)

They say a small outburst occured in mid March. But it is not brighter at all than before.

* 2017 Mar. 3 (6 comets)

I observed 6 comets visually on Mar. 3 in Mt. Hanadate, Ibaraki, Japan.

New comet gb00099 was discovered by Borisov timely, I received the observations from Hidetaka Sato and the preliminary orbital elements from Hirohisa Sato, so I could observe the new comet.

* New comet gb00099 became C/2017 E1 ( Borisov ) officially.

The brightest comet C/2015 V2 was too close to a 4-mag star, so I could not estimate the magnitude, although it was easily visible.

C/2015 ER61 ( PanSTARRS )

10.7 mag   Dia. 1.1'   DC 3-4   (40.0-cm reflector 144x)

Much smaller than expected and I felt it very faint, probably due to the low sky condition.

C/2017 E1 ( Borisov )

12.2 mag   Dia. 1.4'   DC 1-2   (40.0-cm reflector 144x)

Diffuse and near limit. It located in the low sky and in the dense field of faint stars. So maybe I overestimated the brightness.

41P/Tuttle-Giacobini-Kresak

10.4 mag   Dia. 5'   DC 3   (40.0-cm reflector 36x)

Very bright and large. Easy to see with low magnification.

45P/Honda-Mrkos-Pajdusakova

10.7 mag   Dia. 6'   DC 0-1   (40.0-cm reflector 36x)

Bright, but completely diffuse with no central condensation.

73P/Schwassmann-Wachmann 3

fainter than 10.5 mag   Dia. 1.4'   (40.0-cm reflector 144x)

Already one month has passed since the fragment BT was discovered. And now it located in the extremely low sky. So it was not visible.

315P/LONEOS

fainter than 13.5 mag   Dia. 0.8'   (40.0-cm reflector 257x)

Not visible.

* 2017 Feb. 6 (5 comets)

I observed 5 comets visually on Feb. 6 in Mt. Hanadate, Ibaraki, Japan.

I wanted to observe 45P approaching to the earth before full moon.

C/2015 ER61 ( PanSTARRS )

11.4 mag   Dia. 1.2'   DC 3   (40.0-cm reflector 144x)

Diffuse, but well visible.

C/2015 V2 ( Johnson )

11.6 mag   Dia. 2.5'   DC 6-7   Tail 4.5' (p.a. 310 deg)   (40.0-cm reflector 75x)

Fairly bright. Looks nice with a tail.

I felt it became much brighter than January. But my measurement became similar to that in January.

41P/Tuttle-Giacobini-Kresak

13.4 mag   Dia. 0.8'   DC 3   (40.0-cm reflector 144x)

Well visible. I felt it became much brighter than January. But my measurement became similar to that in January.

45P/Honda-Mrkos-Pajdusakova

7.9 mag   Dia. 11'   DC 1   (40.0-cm reflector 36x)

6.9 mag   Dia. 16'   DC 2   (10x70 monocular)

Very bright and easy to see with a small monocular. Diffuse and very very large.

73P/Schwassmann-Wachmann 3

fainter than 12.2 mag   Dia. 1.1'   (40.0-cm reflector 144x)

Not visible.

When guideing my telescope to the comet, I found a bright nebula not recorded in my chart, where I plotted clusters and nebulae down to 12 mag. So I imagined it might be a fragment or new comet. But actually, it was planetary nebula NGC 6445.

* 2017 Jan. 24 (9 comets)

I observed 9 comets visually on Jan. 24 in Mt. Hanadate, Ibaraki, Japan.

Although the sky was covered with heavy clouds in day time, it became completely fine rapidly after the sunset, then it kept fine with no clouds all night. The moon with earthshine in the morning sky was very beautiful.

C/2015 ER61 ( PanSTARRS )

12.2 mag   Dia. 1.1'   DC 3-4   (40.0-cm reflector 144x)

Much fainter and harder to see than expected, probably due to the low sky condition.

C/2015 V2 ( Johnson )

11.9 mag   Dia. 1.7'   DC 6-7   (40.0-cm reflector 75x)

Very strongly condensed and easy to see. Because it located very near by a 11-mag star, maybe the outer coma was not visible.

2P/Encke

12.2 mag   Dia. 1.7'   DC 1-2   (40.0-cm reflector 144x)

Diffuse.

41P/Tuttle-Giacobini-Kresak

13.8 mag   Dia. 0.7'   DC 3   (40.0-cm reflector 144x)

Already visible visually. Small.

43P/Wolf-Harrington

13.6 mag   Dia. 0.6'   DC 2-3   (40.0-cm reflector 144x)

Unexpectedly still visible. Near by a globular cluster M68.

73P/Schwassmann-Wachmann 3

13.7 mag   Dia. 0.6'   DC 2   (40.0-cm reflector 257x)

Unexpectedly, already visible visually.

93P/Lovas 1

fainter than 13.5 mag   Dia. 0.8'   (40.0-cm reflector 257x)

Not visible.

144P/Kushida

13.9 mag   Dia. 0.9'   DC 2-3   (40.0-cm reflector 257x)

Unexpectedly still visible.

315P/LONEOS

14.0 mag   Dia. 0.3'   DC 2   (40.0-cm reflector 257x)

Extremely hard to see.

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Go to Seiichi Yoshida's Diary of Comet Observations in 2016.

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