From my recent diary

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Unless otherwise noted I use the following materials since the end of October, 2018.
D: 45.5cm f: 2037mm Dobsomian (Newtonian reflector)
Eyepiece: and magnification:
Lavendura 63mm, apparent FOV 45 deg. with Paracorr
@@@@@@@@@@@ @               x37, actual FOV 1.2 deg.

Night Vison:
ACT PVS-14 Photonis 4G INTENS 1800 Auto gate P45 WP

Saturday, January 21 to Sunday, January, 22


Drawing a sketch of C/2022 E3 ZTF
Although air temperature was as low as -6ºC, the condition was favorable without wind and clear sky. C/2022 E3 brightened up to 6th magnitude and worth observing. I have observed the lengths of the ion and the dust tails of the comet as 1.5º and 0.5º, respectively, on Tuesday, Jan. 17 using my 46 cm reflector, and I was curious about the present situation of the tails. The appearance of the tails observed by Night Vision, 37x was equivalent with that seen by Ethos 21 mm + Paracorr, 112x. I confirmed the length of the dust tail was 0.5º using a 7x50 mm binocular at this predawn after 4a.m. local time. I tried to detect the comet by naked eye but could not do by any means.

Sketch of C/2022 E3 ZTT Part 1. 46 cm NV 37x.

I had a plan to draw a sketch of this comet this predawn using my 46 cm telescope with NV 37x prior to the comet hunting session. The first impression when I aimed my telescope at the comet was that weirdness of the short tail as short as 40f (refer to the sketch). I wondered if the cause was slightly poor transparency of the sky, but it is unlikely because NV has a tolerance for hazy sky condition due to the extended sensitivity up to infrared area. Anyway, the length had become shorter without doubt. Later, I have learned there was a hypothesis on the reduction of the length via comets-ml. That said the cause was cut-down of the tail due to solar plasma polarity reversal originated from recent solar flare. Comets have a magical power to transform!
Observation by Nick James: C/2022 E3 (ZTF) tail disconnection

Todayfs hunting session
After making a sketch, I started one-and-a-half-hour hunting session from Zubenelgenubi, ƒΏ Librae. There are many galaxies are with 11th magnitude or darker in the constellation of Libera, but few of them are detectable during the session if the sky condition is not good. Thanks to the aid of NV I could identified seven galaxies in total: NGC5898, 5893, 5796, 5878, 5861, 5915 and 5916. Among them the darkest one was NGC5916 with the magnitude of 13.5. Those galaxies along with a diffused globular cluster NGC5916 came into the FOV within 30 minutes from the beginning of the session. In the latter half of the session, I observed 10 globular clusters in the constellation of Scopius and Ophiuchus. One of them, NGC6144, is close to Antares, ƒΏ Scorpii, and one may overlook it dazzled by the brightness of Antares even if the 46 cm telescope is used. Twenty five minutes after the start of the twilight, I identified the last globular cluster during the session, M107, in Ophiuchus.

Although air temperature was -3ºC, I felt it was very cold due to weak wind. Continuing yesterday, I drew a sketch of C/2022 E3. This time I prepared printed map and sketched on it. I noticed the length and the shape of the tails varied in comparison with those of the previous day at a glance. The ion tail extended to 1º in length with a branch downwards. The dust tail also had a branch that looked like a part of an anti tail.

Sketch of C/2022 E3 ZTF Part 2. 46 cm NV 37x.

I began to sketch at 4:20a.m., however, the comet was disappeared because of clouds at 4:35a.m. I resumed to draw the sketch at 4:45a.m. as clouds parted; I noticed the distribution of the brightness in the ion tail was apparently different from that at the beginning of drawing. The movie taken by Nick James showed variation in the ion tail during one hour, and I have confirmed similar temporal variation visually. If I had not been interrupted by the clouds and forced to stop drawing, I would not have noticed the change. Though I could not draw the change, I was amazed and impressed by the fact that I detected the short time variation in the tail visually.

At 4:47a.m. when I completed sketching, clouds increased. At 5a.m.the sky got completely cloudy. I had been waited for clear sky until 6a.m. just after the start of the twilight, but after all the clouds did not break and I could not sweep the sky. The duration of the clear sky was spent only for drawing, but I think I have felt the joy of receiving the comet's living light directly with my own eyes since the time of the discovery of 332P Ikeya-Murakami.

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