Seiichi Yoshida's Diary of Comet Observations (2013)

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Updated on November 17, 2013


Detailed observation data in ICQ format.


* 2013 Nov. 16 (5 comets)

I observed 5 comets visually on Nov. 16 on Mt. Tsukuba, Ibaraki, Japan.

It was foggy on the ground, but it was fine on the mountain. Hard to see comets due to the strong full moon light. But many comets located very near by bright stars, so easy to find.

I started observations from 3 o'clock. But just before the morning twilight began, the full moon became low and the sky became clear. So I estimated all comets again.

C/2012 S1 ( ISON )

6.3 mag   DC 8   (40.0-cm reflector 36x)

5.8 mag   DC 9   (10x70 monocular)

Extremely strongly condensed. Quite different from one week ago! But hard to see the coma and tail due to the low sky haze. It located near by Spica and easy to find.

C/2012 X1 ( LINEAR )

9.0 mag   Dia. 3.5'   DC 1   (40.0-cm reflector 75x)

It located near by Arcturus and easy to find. Maybe I underestimated the size due to the low sky haze.

C/2013 R1 ( Lovejoy )

4.9 mag   Dia. 21'   DC 7   (10x70 monocular)

Very clearly visible despite the full moon. It seems to brighten furthermore during last one week.

P/2013 V3 ( Nevski )

10.1 mag   Dia. 2.7'   DC 3   (40.0-cm reflector 75x)

Some observers reported it as 8 mag. But it is diffuse and fainter than expected.


8.2 mag   DC 8   (40.0-cm reflector 75x)

Extremely strongly condensed and easy to see despite the low sky condition. But hard to see the coma due to the low sky haze. It located near by Mercury and easy to find.

* 2013 Nov. 8 (4 comets)

I observed 4 comets visually on Nov. 8 on Mt. Tsukuba, Ibaraki, Japan.

Although it was cloudy around 3 o'clock, the weather became fine with no clouds until the morning. But clouds came again from the south after the morning glow began, and covered the whole sky until the sunrise.

Many people visited Mt. Tsukuba, probably to observe Comet ISON.

C/2012 S1 ( ISON )

8.3 mag   Dia. 2.8'   DC 7   (40.0-cm reflector 36x)

8.4 mag   Dia. 3.4'   DC 7   Tail 9' (p.a. 290 deg)   (40.0-cm reflector 75x)

It looks very cool with a long tail.

C/2012 X1 ( LINEAR )

8.6 mag   Dia. 4.6'   DC 1-2   (40.0-cm reflector 75x)

Very large and diffuse. It looks well after rising higher.

C/2013 R1 ( Lovejoy )

6.0 mag   Dia. 18'   DC 7   (10x70 monocular)

Very bright! Very large, and very strongly condensed.


7.5 mag   Dia. about 4'   DC 8   (40.0-cm reflector 36x)

I was surprised! Extremely strongly condensed. It looks almost stellar at a glance. Completely different from my last observation in mid October. I wondered if an outburst occured.

* 2013 Oct. 11-13 (11 comets)

I observed 11 comets visually between Oct. 11-13 in Kita-karuizawa, Gunma, Japan.

The weather kept fine all through the holidays.

On Oct. 11, strong wind easily moved my telescope. Half of the sky was covered by heavy clouds. But fortunately, the sky around the comets were clear. The sky was completely fine with no clouds on Oct. 12 and 13.

I also observed Nova Del 2013 (V339 Del), a 4-mag naked-eye nova in August, as 10.1 mag on Oct. 11.47 (UT).

C/2010 S1 ( LINEAR )

Oct. 11   13.8 mag   Dia. 0.8'   DC 5   (40.0-cm reflector 257x)

Oct. 12   13.4 mag   Dia. 0.3'   DC 4   (40.0-cm reflector 257x)

Faint and hard to see. The condensation became weaker than before. Maybe I underestimated the size on Oct. 12 due to a faint star close to the comet.

C/2011 J2 ( LINEAR )

Oct. 11   13.8 mag   Dia. 0.8'   DC 3   (40.0-cm reflector 144x)

Oct. 12   13.4 mag   Dia. 0.8'   DC 4   (40.0-cm reflector 144x)

Oct. 13   13.9 mag   Dia. 0.9'   DC 4   (40.0-cm reflector 144x)

Faint, but visible with averted vision. Well visible on Oct. 12 probably due to the clear sky condition.

C/2011 L4 ( PanSTARRS )

Oct. 11   fainter than 12.6 mag   Dia. 0.9'   (40.0-cm reflector 144x)

Oct. 12   fainter than 12.9 mag   Dia. 1.1'   (40.0-cm reflector 144x)

Oct. 13   fainter than 12.6 mag   Dia. 0.5'   (40.0-cm reflector 257x)

Already too faint to see.

C/2012 F6 ( Lemmon )

Oct. 11   11.7 mag   Dia. 1.4'   DC 4   (40.0-cm reflector 144x)

Oct. 12   11.6 mag   Dia. 1.4'   DC 3-4   (40.0-cm reflector 144x)

Oct. 13   11.7 mag   Dia. 1.2'   DC 4   (40.0-cm reflector 144x)

I could see this comet after almost one year blank. Unexpectedly, the comet is still bright.

C/2012 S1 ( ISON )

Oct. 11   10.4 mag   Dia. 2.2'   DC 4   (40.0-cm reflector 75x)

Oct. 12   9.9 mag   Dia. 3.1'   DC 5   (40.0-cm reflector 75x)

Oct. 13   10.7 mag   Dia. 2.5'   DC 3   (40.0-cm reflector 75x)

My first observation of Comet ISON. Already very bright. I felt somewhat elongated on Oct. 11 and 12. It was well condensed on Oct. 12. However, I felt the comet became diffuse and weakly condensed on Oct. 13.

P/2013 J2 ( McNaught )

Oct. 11   14.3 mag   Dia. 0.5'   DC 5   (40.0-cm reflector 257x)

Oct. 12   fainter than 13.3 mag   Dia. 0.4'   (40.0-cm reflector 257x)

I could see it, probably because the moon was hidden by heavy clouds. Very tiny.

C/2013 N4 ( Borisov )

Oct. 12   10.8 mag   Dia. 1.3'   DC 3-4   (40.0-cm reflector 144x)

Hard to see due to the extremely low location. Brighter than expected. But maybe I overestimated.

C/2013 R1 ( Lovejoy )

Oct. 11   9.3 mag   Dia. 5'   DC 4   (40.0-cm reflector 36x)

Oct. 12   10.4 mag   Dia. 4.5'   DC 5   (40.0-cm reflector 36x)

Oct. 13   9.3 mag   Dia. 6.5'   DC 4   (40.0-cm reflector 36x)

Very bright and large! Smaller than 2P/Encke, but more condensed.


Oct. 11   8.3 mag   Dia. 7'   DC 2   (40.0-cm reflector 36x)

Oct. 12   8.5 mag   Dia. 7.5'   DC 2-3   (40.0-cm reflector 36x)

Oct. 13   8.4 mag   Dia. 8'   DC 2   (40.0-cm reflector 36x)

Very bright and large!


Oct. 11   10.8 mag   Dia. 2.7'   DC 0-1   (40.0-cm reflector 75x)

Oct. 12   11.1 mag   Dia. 1.5'   DC 0-1   (40.0-cm reflector 144x)

Very large, and extremely diffuse. Easily visible on Oct. 11, probably because the moon was hidden by heavy clouds.


Oct. 11   fainter than 13.8 mag   Dia. 0.5'   (40.0-cm reflector 144x)

Oct. 12   fainter than 14.5 mag   Dia. 0.4'   (40.0-cm reflector 257x)

Oct. 13   14.6 mag   Dia. 0.4'   DC 5   (40.0-cm reflector 257x)

Near limit. Looks similar to a faint background stars.

* 2013 Aug. 19 (1 nova)

I observed a bright naked-eye nova discovered by Koichi Itagaki visually on Aug. 19 at home backyard in Ibaraki, Japan.

Nova Del 2013

4.9 mag   (10x70 monocular)

The nova locates in the middle between Delphinus and Sagitta. Bright full moon locates very near by the nova.

* 2013 Apr. 7 (5 comets)

I observed 5 comets visually on Apr. 7 on Mt. Tsukuba, Ibaraki, Japan.

The sky was fine with no clouds and very clear after the storm. Hard to get in focus with high magnification due to the strong wind.

I met several wild boars on the way.

C/2006 S3 ( LONEOS )

13.6 mag   Dia. 0.7'   DC 4   (40.0-cm reflector 144x)

Tiny, but easy to find.

C/2011 L4 ( PanSTARRS )

5.2 mag   Dia. 6'   DC 7   Tail 0.4 deg (p.a. 0 deg)   (10x70 monocular)

Finally, I could see Comet PanSTARRS. It looks very small, but looks cool with a broad tail. I enjoyed the comet with Andromeda Galaxy in the same field of view.

C/2011 R1 ( McNaught )

fainter than 13.0 mag   Dia. 1.6'   (40.0-cm reflector 144x)

Maybe a diffuse comet with DC=2 was visible. But I am not sure.

C/2013 E2 ( Iwamoto )

fainter than 12.3 mag   Dia. 0.6'   (40.0-cm reflector 257x)

Unfortunately, I could not see the comet due to the low sky condition.


13.6 mag   Dia. 1.2'   DC 2   (40.0-cm reflector 144x)

Unexpectedly, I could see the comet still now. The comet is very near by Pinwheel Galaxy M101. I also enjoyed the very large diffuse galaxy.

* 2013 Feb. 15 (2 comets + 1 asteroid)

I observed 2 comets and an asteroid 2012 DA14 visually on Feb. 15 on Mt. Tsukuba, Ibaraki, Japan.

Although it was rainy in daytime, the sky became completely fine around midnight as the weather forecast predicted. Although Tsukuba City was in the dense fog, the sky was clear on Mt. Tsukuba. So I could enjoy the historical close flyby of an asteroid 2012 DA14.

I also tried to observe C/2006 S3, but it was blended with a neaby 12 mag star and I could not oberve.

C/2011 R1 ( McNaught )

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

Difficult to see because locating near by a pair of double stars, but I could see the comet.


10.8 mag   Dia. 2.1'   DC 5   (40.0-cm reflector 144x)

I was filled with deep emotion because finally I could see the long lost comet D/Pons-Gambart. The comet looks well condensed. But anyway, must fainter than I had expected. I had imagined D/Pons-Gambart would be a historical great comet...

2012 DA14

7.1 mag   DC 9   (10x70 monocular)

7.2 mag   DC 9   (40.0-cm reflector 36x)

Easy to find exactly at the predicted position. I was observing it during 20 minutes, but the brightness did not change at all.


Go to Seiichi Yoshida's Diary of Comet Observations in 2012.


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