On Sunday, October 19, 2025, my husband I drove back to Sargent, Texas for darker skies (Bortle 4) and another try at Comet C/2025 A6 Lemmon.  Happily, this time the sky was clear and I successfully captured the comet with my small telescope.  I was also successful in seeing it with binoculars.  I was less successful with a wide angle shot with my camera on a tripod – the comet was not obvious and I was fooled by internal reflections of some bright green lights on the horizon.  I’m going to spend some more time with those images, but I’m not hopeful of pulling out a nice comet picture from them.

Based on this experience, I was pretty sure the comet would not be naked eye visible even from Bortle 4 skies at its closest approach to Earth on October 21. 

As the comet got closer to Earth, its relative angular motion increased.  I didn’t want the comet to “smear” in the pictures, so I was taking shorter frames based on the comet only moving a half pixel per frame.  There’s a trade-off, though, between completely freezing the comet’s motion in a frame and capturing enough light to separate the comet’s tail from the background noise.  In this case, I think the frames were too short – the comet’s coma and tail are many pixels wide, and I probably should have accepted some motion in exchange for collecting more data.  This also wasn’t much data: 6.25 minutes of red data, 6.4 minutes of green data, and 5.75 minutes of blue data.  

The comet still got better from here … but it’s taking a while to get these images processed.  More to come!

Camera geek info – telescope:

• William Optics Zenith Star 73 III APO telescope
• William Optics Flat 73A
• ZWO 2” Electronic Filter Wheel
• Antila RGB filters
• ZWO ASI183MM-Pro-Mono camera
• William Optics Uniguide 32MM F/3.75
• ZWO ASI220MM-mini
• ZWO ASiair Plus
• iOptron CEM40
• Sargent, Texas Bortle 4 skies

Frames – telescope:

• October 19, 2025
  • 75 5 second Gain 150 R lights (56 for stars)
  • 30 0.05 second Gain 150 R flats
  • 77 5 second Gain 150 G lights (48 for stars)
  • 30 0.02 second Gain 150 G flats
  • 69 5 second Gain 150 B lights (34 for stars)
  • 30 0.02 second Gain 150 B flats
  • Matching darks and flat darks from library