Watching the comet

 Last night I actually watched the comet with a telescope rather than relentlessly photograph it.  I used a 4.25-inch (108 mm) f/3.7 reflector whose mirror I ground and polished as a teenager over 55 years ago.  With a 24 mm eyepiece in the drawtube the magnification was about 17x.  

One takeaway from the visual observing was just how many satellites were continually zooming through the field of view.  We are rapidly losing an unimpeded view of the night sky.

Of course, I also had a camera set up.  I used a Sony A7iii camera and a Nikon 180mm f/2.8 ED Ai-s lens.

Comet C/2025 A6 (Lemmon), 21 Oct.

 

Photobombed by satellites!

The orbital velocity of a comet can be quite high as it nears the sun.  The following animation shows that the motion against background stars is evident over a period of only 20 minutes.

20-min time span.

 

Comets Lemmon and SWAN, Monday evening

 I dragged myself outside this morning to get pictures of Comet C/2025 A6 (Lemmon) around 6 am MDT.  One of those pictures is in the previous post.  That is likely the last time, because as the comet gets closer to the sun the sky is getting too bright by the time it rises above the distant ridgeline.  In the evening, the comet is still easily visible above Bristol Head as darkness falls and is very near its expected peak brightness of magnitude 4.  That is naked-eye brightness, but it is much better observed with binoculars.

For a change of pace, this evening I used a Sony A7iii camera with a Nikon 180mm f/2.8 ED Ai-s lens.

Comet C/2025 A6 (Lemmon) over Bristol Head. 7:50 pm MDT 20 Oct.

 

Comet Lemmon. 8:00 pm MDT 20 Oct.

Comet C/2025 R2 (SWAN). 8:05 pm MDT 20 Oct

The name "Lemmon" derives from the Mount Lemmon Observatory in the Santa Catalina Mountains.  The name "SWAN" derives from the Solar Wind Anisotropies (SWAN) instrument on the ESA Solar and Heliospheric Observatory (SOHO) spacecraft.

Comets in the morning, comets in the evening

 At any given time, it is normal for there to be a dozen or more comets within photographic range.  More rarely, one or more of these comets will be bright enough to be seen with the unaided eye or with small optical instruments such as binoculars.  There are currently two "bright" comets: C/2025 A5 (Lemmon), near magnitude 4, and C/2025 R2 (SWAN), near magnitude 6.  Comet Lemmon has been visible in the both the morning and evening sky.  Comet SWAN is an evening-only object.

The following images were obtained over the past three days with an Olympus 75mm f/1.8 lens and a Rokinon 135mm f/2 lens. 

Morning Comet Lemmon rising over Snowshoe Mt.  6:05 am MDT, 20 Oct.

 

Morning Comet Lemmon, 5:48 am MDT, 18 Oct.

The wispy tail extends about 3°.  5:48 am 18 Oct.

Morning Comet Lemmon, 5:41 am 18 Oct.

Evening Comet Lemmon over Bristol Head.  7:45 pm 18 Oct.

Comet C/2025 R2 (SWAN) is the green blob in the upper-left corner. 18 Oct.

Comet SWAN is currently traversing across the Milky Way.  The nebulae M16 and M17 are on the right-hand side of the above image.  The green glow of the comet is from the emission of diatomic carbon (C₂).

A closer look at Comet SWAN on 19 Oct.

One of the fainter comets is C/2024 E1 (Wierzchos), near magnitude 13.  It is just recognizable as a faint blob at the center of this 60 sec exposure:

Comet C/2024 E1 (Wierzchos), 19 Oct.

 

Evening Comet Lemmon, 7:40 pm MDT, 19 Oct.

Comet C/2025 A6 (Lemmon) setting over Bristol Head

At my location the mountains to the west rise up to about 12°  above the horizon.  There was a fairly narrow time window, about 20 minutes, between the end of Nautical Twilight and when the comet set behind the Bristol-Head mountain ridge.

Comet C/2025 A6 (Lemmon) above Bristol Head.  Olympus 75mm f/1.8, ISO 800, 30 s.

 

Rokinon 135mm f/2, ISO 1600, 60 s.

Photo-bombed by satellites!  Not much time for a do-over, the comet is about to slip behind the ridgeline:

Rokinon 135mm f/2, ISO 1600, 30 s.

 The comet's tail seems to extend about 2° in these short exposures.

Comet C/2025 A6 (Lemmon) near dawn

 At 5:15 am the waning crescent moon was rising over Snowshoe Mountain and Comet Lemmon (C/2025 A6) was low in the northeastern sky.  When I set up the cameras it was still too dark to see that the northern view was obstructed by power lines.  I am sure that there is some fancy post-processing that can remove the power-line shadows, but next time I will just scout out a better location ahead of time.

The comet is currently at about magnitude 4.5, which makes it a naked-eye object.  However, it is tough to see through the low-elevation airglow murk.  It was easy to pick up with binoculars. 

Olympus 75mm f/1.8.  ISO 1600, 30 s.

 

Rokinon 135mm f/2.  ISO 1600, 40 s.

There are two galaxies visible in this image to the upper-right  and right of the comet: NGC 5005 and NGC 5033, respectively.

Star trails over Bristol Head

 The waning Harvest Moon lit up the landscape for this two-hour exposure.  A lot of airplane trails are visible—hard to avoid during this 9–11 pm time period.  Olympus E-M1iii + Leica 9mm f/1.7.

The next morning:

 

Harvest Moon rising

 The full moon that occurs closest in time to the Autumnal Equinox (September 23) is known as the "Harvest Moon".   This name is appropriate, of course, only for the northern hemisphere.  This year the 06 October full moon is also a so-called "supermoon", a much over-hyped distinction.

Here is the Harvest Moon rising over Snowshoe Mountain.  Astro-Tech AT80EDT f/6 refractor.

 And setting the next morning behind Bristol Head:

 

Observe the Moon Night

 "Observe the Moon Night" is a NASA-sponsored event that occurs each fall on a weekend when the moon is near first-quarter phase.  This year it occurred yesterday, 04 October.  The moon last night was 12.6 days old, about five days past first quarter.

 

telescope: Astro-Tech AT80EDT f/6

A morning comet: C/2025 A6 Lemmon

 Comet C/2025 A6 Lemmon is in the morning sky east of the Big Dipper.  It is approaching naked-eye visibility, but not quite there yet.  It is currently at magnitude 6.7 and is predicted to get as bright as magnitude 3 by the end of the month.  It has a green head and a blue ion tail.

These images were obtained after 4 am on 02 Oct.

 

Rokinon 135mm f/2.

comet C/2025 A6 Lemmon (circled).  Sigma 30mm f/1.4 + softon.

Credit: SkySafariAstronomy.com

The measured sky brightness was sqml=21.27.  The comet was just above the airglow murk along the northeast horizon.

There were other things to look at as well:

Sirius rising over Snowshoe Mountain.  Sigma 30mm.

 

Rosette Nebula (and cluster NGC 2244).  Rokinon 135mm f/2.

Centered on the Rosette Nebula. (Credit: SkySafariAstronomy.com)