Comet C/2025 A6 Comet Lemmon was an excuse to do something I’ve been wanting to do for a long time: go watch the sun set over the Fred Hartman Bridge in Baytown, Texas.  The Fred Hartman Bridge is a gorgeous, yellow, cable-stayed bridge that I always enjoy driving over when I get the chance.  

I had hoped that the bridge would make a great foreground for a comet picture.

We got to our viewing spot early so we could also enjoy the sunset, which did line up beautifully with the bridge.  I met a nice couple there who were also watching the sunset, and I enjoyed chatting with them.

Unfortunately for my comet and star viewing plans, looking west over the bridge is also looking straight into a bunch of brightly lit refineries.  (There is apparently no collective noun for refineries, but I think there should be one.  How about a process of refineries?  Other suggestions?)

So that evening, I could not spot the comet and could barely spot even the brightest stars.  I took a bunch of pictures anyway, but even when it was fully dark, I was limited to 2 second long images.  I did not have much hope that I would be able to generate a picture with visible stars, much less a visible comet.

So I let other astro processing take priority.  

When I finally got around to processing these images, I started with the last 100 frames, and, to my surprise and delight, I could see the comet!  So then I went back and processed all 553 frames of 2 second data, 403 of which (13.4 minutes of data) were usable.  I processed the comet separately from the stars to get as much of it as possible.  Then I overlaid the stars and comet over a single image of the bridge at night and a single image of the bridge at sunset.  

Which do you like better?

Camera geek info stars and night image:

• Canon EOS 60D in manual mode set 2 second exposure, ISO 800
• Sigma 24-70 mm f/2.8EX lens, set at f/5.6, 24 mm, manual focus for stars and night version
• Tripod
• Intervalometer 

Camera geek info Sunset:

• Canon EOS 60D in manual mode set 4 second exposure, ISO 100
• Sigma 24-70 mm f/2.8EX lens, set at f/9, 24 mm, manual focus for stars and night version
• Tripod
• Intervalometer 

Frames:

• November 2, 2025
  • 1 4 second light for sunset
  • 403 2 second lights for stars and comet
  • 31 1/1250 second flats
  • 33 1/2500 second darks from library
  • 57 1 second darks from library