Here is the frame of comet C/2023 A3 taken at the night:
www.flickr.com/photos/hiroc/53657326751

site: 1,232m above sea level at lat. 36 55 68 North and long. 139 44 57 East near Mt. Keicyo Tochigi 栃木県 鶏頂高原. Transparency was not good. Small fog drops were visible drifting slowly in light beam time to time. Ambient temperature was around 5 degrees Celsius or 40 degrees Fahrenheit. SQM-L reached 21.22 at the night. Wind was mild, though atmospheric turbulence was not fair. Guide error RMS was around 1."

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Weather forecast was nice for the weekend, and I tried long exposure session of the comet for more than 3 hours.

The comet was drifting toward west a bit northward in Virgo. It got bigger and brighter than before. Dust coma was round and small. Dust jets were visible toward north northeast and south southwest in short exposure frames, and the dust area showed not round shape but longer toward north northeast and south southwest. Dust tail got clearer and longer than before toward east northeast. The shape was like a "," comma in total at the night.

Ion activity was detected faintly. The area had greenish tint in color enhanced frame.

Here is a frame of the comet taken on March 7, 2024:
www.flickr.com/photos/hiroc/53572742800

Here is a frame of the comet in Virgo taken on April 8, 2023:
www.flickr.com/photos/hiroc/52809324098

Earth Distance: 2.006 AU
Sun Distance: 2.996 AU

equipment: Guan Sheng Optical Ritchey–Chrétien telescope RC-CF 10" f8, TS Extension for The Baffle Tube, TS 2.5" field flattener, and Canon EOS 5Dmark3-SP4, modified by Seo-san on SkyWatcher CQ350 Pro Equatorial Mount, autoguided at a star nearby with Fujinon 1:2.8/75mm C-Mount Lens, Pentax x2 Extender, ZWO ASI 120MM-mini, and PHD2 Guiding with comet tracking on

exposure: 7 times x 1,200 seconds, 7 x 240 sec, 6 x 60 sec, and 19 x 15 seconds at ISO 6,400 and f/8

The exposure started at 15:37:10 and ended at 18:44:15 UTC April 13, 2024.

This frame was cropped 4,927 x 3,290 pixels of the original 5,760 x 3,840 pixels, comparable to a frame taken with a telescope of focal length about 2,300mm.

site: 1,232m above sea level at lat. 36 55 68 North and long. 139 44 57 East near Mt. Keicyo Tochigi 栃木県 鶏頂高原. Transparency was not good. Small fog drops were visible drifting slowly in light beam time to time. Ambient temperature was around 5 degrees Celsius or 40 degrees Fahrenheit. SQM-L reached 21.22 at the night. Wind was mild, though atmospheric turbulence was not fair. Guide error RMS was around 1."

Here is a view of the site and my equipment at the night:
www.flickr.com/photos/hiroc/53659463938

Tags:   紫金山アトラス彗星

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I drove 4 hours through cloudy area toward north in the afternoon, and I could enjoy imaging of the comet. Scattered clouds interfered the session time to time. The comet low in the west and sank beyond clouds before the end of twilight.

Here is the pic of the comet, 12P Pons-Brooks taken at the site:
www.flickr.com/photos/hiroc/53641876005

site: 100m above sea level at lat. 38 35 20 North and long. 140 44 18 East in the rice field near Mt.Yakurai Miyagi 宮城県 薬莱山. Ambient temperature was around 8 degrees Celsius or 46 degrees Fahrenheit. Wind was mild, though atmospheric turbulence was awful as in the season here. Guide error RMS was around 3."

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I drove 4 hours through cloudy area toward north in the afternoon, and I could enjoy imaging of the comet. Scattered clouds interfered the session time to time. The comet was low in the west and sank beyond clouds before the end of twilight.

The comet was drifting toward west southwest in Aries. Dust coma was round and bright. Dust tail was vague. Bluish green ion halo was round and beautiful. Ion tail was long beyond the upper edge of the frame showing blue and yellow colored multiple steams.

It passes the perihelion at 0.777 AU on April 23, 2024.

Sun Distance: 0.842 AU
Earth Distance: 1.610 AU

equipment: Takahashi FSQ-106ED, 645 Reducer, EOS R6-SP5, modified by Seo-san on ZWO AM5 Mount, autoguided with TS 32 mm Mini Guide Scope, focal length 120mm, ZWO ASI 120MM-mini, and PHD2 Guiding with Comet Tracking on

exposure: 3 times x 180 seconds, 5 x 90 sec. 11 x 30sec, 10 x 15 sec, 9 x 4 sec, and 10 x 1 second at ISO 1,600, focal ratio f/3.6, and focal length 380mm

The exposure started at 9:55:20 UTC April 4, 2024 and ended before the end of twilight.

site: 100m above sea level at lat. 38 35 20 North and long. 140 44 18 East in the rice field near Mt.Yakurai Miyagi 宮城県 薬莱山. Ambient temperature was around 8 degrees Celsius or 46 degrees Fahrenheit. Wind was mild, though atmospheric turbulence was awful as in the season here. Guide error RMS was around 3."

Here is a view of the site at the night:
www.flickr.com/photos/hiroc/53644423123

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This frame is another mixture of frames taken with dual narrow band filter and without such filter. I changed balance of them. I made wide band frame far stronger in this version, though the exposure was not enough. I believe long exposure at dark site essential.

Hydrogen-alpha emissions were rich here.

Here is a closer frame of Pleiades and Surrounding Hydrogen-alha Emissions December 2023:
www.flickr.com/photos/hiroc/53420474382

data with dual narrow band filter as below:

equipment: Askar FMA180 Pro, Optolong L-ultimate Dual 3nm Filter, and Canon EOS R6-SP5, modified by Seo-san on ZWO AM5 Equatorial mount, autoguided with Fujinon 1:2.8/75mm C-Mount Lens, ZWO ASI 120MM-mini, and PHD2 Guiding on Genuine Tripod

exposure: 10 times x 1,800 seconds, 15 x 240 sec, and 23 x 60 seconds at ISO 6,400 and f/4.5

site: 1,350m above sea level at lat. 36 26 30 North and long. 138 32 16 East near Volcano Asamayama 浅間山 The site was about 4km from the center of the erupting crater. Ambient temperature was around -3 degrees Celsius or 27 degrees Fahrenheit. Sky was darker than usual, SQNL 21.22 at the night.

data with clear filter as below:

equipment: Askar FMA180 Pro, Canon Clear Filter, and Canon EOS R6-SP5, modified by Seo-san on ZWO AM5 Equatorial mount, autoguided with Fujinon 1:2.8/75mm C-Mount Lens, ZWO ASI 120MM-mini, and PHD2 Guiding on Genuine Tripod

exposure: 8 times x 600 seconds, 5 x 240 sec, and 6 x 60 seconds at ISO 1,600 and f/4.5

site: 1,467m above sea level at lat. 35 55 54 North and long. 138 24 25 East near Mt.Yatsugatake 東沢大橋展望台駐車場. SQML was up to 21.27. Ambient temperature was around -7 degrees Celsius or 19 degrees Fahrenheit. Wind was mild. Atmospheric turbulence was awful as in the season, and guide error RMS was bad, around 1.2."

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