Moon, comet, star clusters

 The moon is 8.7 days past new, waxing gibbous, and lighting up the sky.  The faux-daylight blue is very strong in photographs.  I used three lenses tonight: Olympus 75mm f/1.8, Canon FD 300mm f/4 L, and an Astro-Tech AT80EDT f/6 refractor (480 mm focal length).

GIbbous moon through the double-pane bedroom window.  AT80EDT.

 

C/2025 A6 (Lemmon) over Bristol Head.  Olympus 75mm.

Canon FD 300mm.

AT80EDT

Just for fun, while I had the telescope mounted (on a ZWO AM3), I snapped some pictures of a couple star clusters.  The bright moonlight is not ideal. However, the measured sky brightness was sqml=20.28, which is darker than a moonless night in Santa Fe. Both exposures: 30 sec, unguided.

M13, a famous globular cluster in the constellation Hercules.

 

M11, the "Wild Duck Cluster", an open cluster in Scutum (part of the Milky Way).

Wednesday comet

 The evening sky remains clear, and in spite of the moon, Comet Lemmon is still an attractive target.  Trying out different lenses keeps things from getting too repetitive.  Tonight I used the Canon FD 300mm f/4 L lens at its native focal length with a Sony A7iii camera on a ZWO AM3 mount. These are unguided 30-sec exposures.

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

It is challenging to get a picture that is not crisscrossed with satellite trails.  These two images were selected from a total of 16.

 

Three comets Tuesday night

 The sky was bright with the first-quarter moon (6.8-d) on Tuesday night.  Even so, I was able to photograph three comets using an old Canon FD 300mm f/4 L lens with a Metabones 0.71x Speed Booster on an Olympus E-M1iii camera.  The resultant focal length is 213 mm @ f/2.8.  The camera was mounted on a ZWO AM3 harmonic drive.

I followed comet C/2025 A6 (Lemmon) visually with a 2x54 wide-field binocular.  The magnitude-4 coma was easy to see and a short trace of the tail was visible in the moonlight.

comet C/2025 A6 (Lemmon).  Canon FD 300mm f/4 L @ 213 mm f/2.8.

about to set behind the Bristol Head ridgeline

 Comet C/2025 R2 (SWAN) is currently in the constellation Aquarius.  It is about magnitude 7 and is decreasing in brightness.

comet C/2025 R2 (SWAN)

 Comet C/2024 E1 (Wierzchos) is in the constellation Hercules.  It is about magnitude 13 (very faint), but is increasing in brightness.

Comet C/2024 E1 (Wierzchos) is the green blob at the center of the image.

 

Monday-evening comet

Comet C/2025 A6 (Lemmon) is still visible, even with the 5.8-day moon high in the south last night.  I watched it with a 2x54 wide-angle binocular and a 60mm f/6 refractor at 12x.  Some wide-angle photographs were obtained with an old Minolta MD 85mm f/2 lens on a Sony A7iii camera and an Olympus 75mm f/1.8 lens on a E-M5iii camera.

Minolta MD 85mm

 The triangle of stars to the right of the comet are Gamma, Kappa, and Beta in the constellation Serpens Caput.

Olympus 75mm 

 

Olympus 75mm

Even with the moonlight it is still possible to pick out the two distinct tails: the narrow blue ion tail and the broader yellow dust tail.

Moonlight makes comet viewing difficult

The 4.9-d moon was still in the sky as Comet Lemmon set behind Bristol Head.  This extra illumination makes viewing and photographing the comet more difficult.  I could still see the bright coma without optical aid, but the tail will become harder to see as the moon becomes brighter night by night.

Photographed with a Sony A7iii + Samyang 85mm AF f/1.4 FEII lens.

Comet C/2025 A6 (Lemmon) setting over Bristol Head, 26 Oct.

 

Comet Lemmon: it keeps getting better

 I just returned from three nights in the big city (Santa Fe), during which there was no comet viewing.  The sky tonight (25 Oct) was mostly clear at dusk.  The crescent moon was partially obscured by thin clouds as it sank behind the Bristol Head ridgeline.

Comet C/2025 A6 (Lemmon) is now brighter than magnitude 4.  I was able to see it without optical aid as it hung low over Bristol Head at the end of Astronomical Twilight.  With a camera, the view is magnificent.  The blue ion tail currently spans more than 7°, and it is twisted and broken by the solar wind.

Sony A7iii + Nikon 180mm f/2.8 ED Ai-s.

 

Olympus E-M5iii + Rokinon 135mm f/2.

Comet C/2025 R2 (SWAN) is still there, but fading, in the southern sky.  At magnitude 6.6, it is not visible without binoculars or a telescope.

 

Comet SWAN.  E-M5iii + Rokinon 135mm.  5.5° FOV.

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: