On Sunday, October 19, 2025, my husband I drove to Sargent, Texas for darker skies (Bortle 4) and another try at Comet C/2025 A6 Lemmon.  In addition to capturing the comet with my telescope and seeing it with binoculars, I tried to capture it with my camera on a tripod.  I didn’t think the comet was going to end up being visible in the widefield image, but it turned out that it was!  

These widefield images require more processing than comet and star field images or deep space object images for a number of reasons.  First, because the camera is on a tripod instead of a tracking mount, the stars and comet “trail” even with these short 10 second subframes.  In this case, I fixed that by using BlurXterminator (BXT) correction only prior to registering and comet aligning the subframes (which takes a lot of computer time), by running BXT a second time after integrating the star sub-frames into a single image, and by running a small size convolution on the stars.  This gave me bigger, but rounder stars, which for a widefield image is what I wanted.  Second, because the comet is moving relative to the stars, it needed to be aligned separately; this is a common step with comet processing that is unnecessary for deep space objects.  Third, because the images included the foreground and a sky gradient, I had to make sure the foreground didn’t throw off any of the astroimage processing.  I did this by removing the foreground from all the subframes, processing the comet and stars, picking one foreground to use and processing it, and then combining them back together.  So this is a composite image with the stars, comet, and foreground processed separately.

This image was made from 74 10 second subframes, for a total integration time of 12.33 minutes of time.  

Imagine what you could see if your eyes could collect data for 12 minutes!

I have really enjoyed photographing this comet; there are more images to come!

Camera geek info – camera:

• Canon EOS 60D in manual mode set at f/3.2, 10 second exposure, ISO 800
• Sigma 24-70 mm f/2.8EX lens, set at 24 mm, manual focus
• Tripod
• Intervalometer 

Frames – camera:

• October 19, 2025
  • 74 10 second lights
  • 30 1/1250 second flats
  • Matching darks and dark flats from library