2024g3 20250113 tlovejoy

C/2024 G3 (ATLAS) Jan 13.965, 2025 UT: I was fortunate enough to image both C/2024 G3 and Mercury almost simultaneously high up in the daytime sky today from my home at Birkdale, QLD, Australia. This enabled me to get a good handle on the true brightness of the comet without having to worry about atmospheric extinction, etc. The verdict? Comparing the green channel of 2 equally exposed images the comet was 1.4 mags brighter than Mercury, or mag -1.8. I used a measurement aperture of 1.0'. Here is what that looks like: with identical crops (20' square FOV) and brightness stretch