Comet C/2025 A6 Lemmon October 23, 2025
The comet was drifting fast toward east southeast in Bootes. It was approaching the perihelion, and the activity got stronger remarkably especially in ion or gas, though it looked smaller than before due to the increasing distance from Earth.
Whitish bright dust coma was small and round. Yellowish dust tail was long toward north northeast with bowing toward west. Greenish ion halo was elongated toward north around proximal part of dust tail widely toward west. Bluish ion tail was straight and long toward north northeast showing striking knot or disconnection and unilateral faint and fine ramifications or streams like rays only toward east. North is up, and east is to the left.
Sun distance: 0.648 AU ( 14% distant from the perihelion )
Earth distance: 0.606 AU ( 8.8% distant from the minimum )
Equipment: Takahashi FSQ-130ED, F3 Reducer 0.6x, IDAS Clear Filter, and EOS R-SP4II, modified by Seo San on ZWO AM5n Equatorial Mount, autoguided with Fujinon 1:2.8/75mm C-Mount Lens, Pentax x2 Extender, ZWO ASI 174MM-mini, and PHD2 Guiding with comet tracking on.
Exposure: 4 times x 30 seconds, 7 x 15 sec, 6 x 4 sec, and 8 x 1 second at ISO 1,600 and f/3.0, focal length 390mm
Exposure started at 08:57:02 October 23, 2025 UTC, 28 minutes before the end of twilight, and it ended at 09:11:08 UTC, 14 minutes before the end of twilight due to encroached dense clouds. Clouds encroached frequently while the imaging session. The object was already low in the west before the end of twilight, and the imaging sessions were busy and restless. I began exposure from shorter sessions before it got dark enough, and longer sessions more than one minute got impossible due to encroached dense clouds.
Site: 1,140m above sea level at lat. 35 24 33 North and long. 138 38 24 East in Asagiri near Mt.Fuji. Ambient temperature was around 7 degrees Celsius or 45 degrees Fahrenheit. Wind was mild. Atmospheric turbulence was not so good, and guide error RMS was around 1.3. Sky was not so dark as you see, SQML around 20.42.
Here is a view of the site at the night:
www.flickr.com/photos/hiroc/54875646726/
Comet C/2025 A6 Lemmon October 23, 2025
The comet was drifting fast toward east southeast in Bootes. It was approaching the perihelion, and the activity got stronger remarkably especially in ion or gas, though it looked smaller than before due to the increasing distance from Earth.
Whitish bright dust coma was small and round. Yellowish dust tail was long toward north northeast with bowing toward west. Greenish ion halo was elongated toward north around proximal part of dust tail widely toward west. Bluish ion tail was straight and long toward north northeast showing striking knot or disconnection and unilateral faint and fine ramifications or streams like rays only toward east. North is up, and east is to the left.
Sun distance: 0.648 AU ( 14% distant from the perihelion )
Earth distance: 0.606 AU ( 8.8% distant from the minimum )
Equipment: Takahashi FSQ-130ED, F3 Reducer 0.6x, IDAS Clear Filter, and EOS R-SP4II, modified by Seo San on ZWO AM5n Equatorial Mount, autoguided with Fujinon 1:2.8/75mm C-Mount Lens, Pentax x2 Extender, ZWO ASI 174MM-mini, and PHD2 Guiding with comet tracking on.
Exposure: 4 times x 30 seconds, 7 x 15 sec, 6 x 4 sec, and 8 x 1 second at ISO 1,600 and f/3.0, focal length 390mm
Exposure started at 08:57:02 October 23, 2025 UTC, 28 minutes before the end of twilight, and it ended at 09:11:08 UTC, 14 minutes before the end of twilight due to encroached dense clouds. Clouds encroached frequently while the imaging session. The object was already low in the west before the end of twilight, and the imaging sessions were busy and restless. I began exposure from shorter sessions before it got dark enough, and longer sessions more than one minute got impossible due to encroached dense clouds.
Site: 1,140m above sea level at lat. 35 24 33 North and long. 138 38 24 East in Asagiri near Mt.Fuji. Ambient temperature was around 7 degrees Celsius or 45 degrees Fahrenheit. Wind was mild. Atmospheric turbulence was not so good, and guide error RMS was around 1.3. Sky was not so dark as you see, SQML around 20.42.
Here is a view of the site at the night:
www.flickr.com/photos/hiroc/54875646726/