Two Comets; My Best Photos of Lemmon and SWAN

Comet Lemmon

Yesterday I posted my best photo of comet Lemmon with hopes that I would be able to image it at least one more time from my home with my larger telescope. As I watched the clouds thickening and moving in from the west and south, prospects for getting a good image of the comet were dwindling. The Windy app was showing the situation to get worse as time draws on. At 5:00pm I decided to power off the telescope and pack things up.

I went out to check on my dogs at 5:40 and wouldn't you know it, the skies over the western horizon were relatively clear - still some very thin high clouds but nothing like it was looking earlier. I checked Windy's satellite feed and yep, a clearing that would last about an hour or so. I went into full gear setting up the equipment at record speed. Making matters even more challenging I decided to configure the telescope in the Hyperstar configuration, allowing me fast optics (f/2) and wide field. This required me to remove the secondary mirror from the front of the scope, add the Hyperstar lens and mount my ASI533 camera. Focus had to be drastically changed, but what could I point to since it was still rather light. The moon of course! Got the focus set pretty good and before I went into the house located a bright star near where the comet would be to get the focus dialed in as best as I could (the autofocuser on my Edge wasn't working so I had to focus by hand).

I think the effort was worth it all as I finally got some pretty good data on the comet's tail. I took 10 second, 30 second and 60 second subs before the comet went behind my tree line. I decided to use only the 30 and 60 second ones.

Processing was a real effort as the CometAlignment tool in PixInsight refuses to lock onto the overexposed comet nucleus. I went with Astro Pixel Processor (APP) which I use almost exclusively for calibrating and stacking comet images. APP worked like a charm and I used PixInsight to finish the process.

Comet C/2025 A6 (Lemmon) - October 27, 2025
EdgeHD11-Hyperstar / ASI533mc Camera
40x30sec and 8x60sec subs

Comet SWAN

You might recall that back in October I discussed the fact that two comets would be visible in the skies at the same time. Lemmon turned out to be the best by far, but SWAN was visible in small telescopes. On October 23rd I did image comet SWAN. There was only the hint of a very small tail but the halo around the comet's head came out rather nicely.

Comet C/2025 R2 (SWAN) - October 23, 2025
William Optics ZS61 - ASI533mc
48x60sec subs

The next few days look to be cloudy, with clearer skies forecasted for Friday and Saturday. Comet Lemmon will reach perihelion on November 8, 2025.That’s the date when it comes closest to the Sun—about 0.53 astronomical units (AU), or roughly 49.25 million miles away. This marks the peak of its solar proximity and typically coincides with its brightest appearance in the sky. But it will also be sinking lower in the WSW skies making it difficult, if not unlikely, to be seen clearly from my home. I may try at the church property with my portable scope(s).

As shown below, comet Lemmon will still be visible for the next couple of weeks, but it will be losing altitude about 5° every 3 days (about 20° on the 28th to only 5° on Nov 12). The chart shows the position of the comet at 7:30pm EDT from October 28 to Nov 12, 2025, with each horizontal line representing 5° of altitude (Note: comet location against the stars is not accurate in this view).