C_2025_K1_ATLAS_RASA11_asi6200mcP_30x90sec_2025_10_29_060125local_JuneLake_California_USA_DEBartlett

Project Notes:

Second day showing SPCC calibrated stars with C/2025 K1 (ATLAS) exhibiting similar gold-red-brown color.
Standard processing steps for me.
I believe the comet coloration is real.
Mentioned by Qicheng Zhang that this comet is low in carbon compounds from an article from The Astronomer’s Telegram read here
Only two other comets have been found to have lower ratios of carbon to hydroxide ions. (same read)
Biver Nicolas indicated that H2O+ ions are usually red in color but longevity is uncertain in plasma tails.
Why did this small comet, with an extremely low absolute brightness, below the typical Bortle limit of survivability, survive and continue past the October 8 2025 perihelion date?
Color saturation in the “CometAligned_StarlessIntegrated_30x90seconds” image is quite evident although no additional saturation has been added. Color calibration steps only.
45 minutes of exposure time.
Lime green coma still present (see yesterday’s image)
My photometric comet observations using yesterday’s standards in Tycho-Tracker indicates a whopping magnitude drop of 0.8 to a now magnitude of 9.0.
The plasma tail and wide fan shaped tail is extensive in this 3.0 long FOV.
This comet looks unfamiliar to me.

Observational Notes:

scope: RASA11 fl620mm F/2
Camera: asi6200mcP
Seeing: 3.5/5
Transparency: 7.5/10
Observer: DEBartlett
Place: JuneLake California USA (Altitude +2357m)
Image Info (widefield BIN2x2),

(All images processed solely using PixInsight, Comet Photometry using Tycho-Tracker)

Image: 30x90sec
Resolution ............... 2.506 arcsec/px
Rotation ................. -2.930 deg
Field of view ............ 3d 4' 49.2" x 1d 33' 46.6"
Image center ............. RA: 11 36 50.112 Dec: +2 39 01.51
📷 C2025 K1 (ATLAS)ImageViewer.png

C/2025 K1 (ATLAS)

ICQ line:

IIIYYYYMnL YYYY MM DD.DD eM/mm.m:r AAA.ATF/xxxx /dd.ddnDC /t.ttmANG ICQ XX*OBSxxf InT APERTURcamchip SFW C ## u.uu xx.x PIXELSIZE

2025K1 2025 10 29.52 C 9.0 AR 28.0T 2A980 7.3 2.65 286 ICQ XX BAR I C 7.26mZCP IMX TYT 0 U9*0.09 9.3 2.5s 2.5 Location: JuneLakeBirdHouse (MPC XXX); Comment: Comet Alt. 21.2

COD XXX

OBS

CATALOG: ATLAS2 - BAND: r (Sun Mag=-26.93)

10x10 20x20 30x30 40x40 50x50 60x60 RSR FC COD

COMET UTC +/- +/- +/- +/- +/- +/- N FWHM CAT

------------ ------------------- ----- ----- ----- ----- ----- ----- ---- ---- ---

C/2025 K1 29/10/2025 12:28:57 11.26 10.54 10.23 10.03 9.89 9.79 179.5 17.5 XXX

C/2025 K1 29/10/2025 12:28:57* 0.08 0.08 0.08 0.08 0.08 0.08 22 29.3 ATL

AFRHO LOG

COMET UTC DELTA r AP " MAG RSR CM +/- AFRHO OBS

------------ ------------------- ----- ----- ----- ----- --- ----- ---- ----- ---

C/2025 K1 29/10/2025 12:28:57 0.89 0.67 31.12 10.20 180 440 67 2.644 XXX📷 C2025_K1(ATLAS) AFRHO.png