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)

Three planets, or two majors plus a dwarf

 The dwarf-planet Ceres was discovered in 1801.  It was originally considered to be the eighth known planet and the fifth planet out from the sun, filling the space between Mars and Jupiter that is now known as the "asteroid belt".  It was eventually reclassified as a new type of object called "asteroid" when additional bodies were discovered in that orbital region. It was reclassified again as a "dwarf planet" at the same time that Pluto was demoted from planet to dwarf-planet status.  Pluto is currently the largest-known dwarf planet and Ceres is the smallest.

Neptune, the eighth major planet and the one farthest from the sun, was not discovered until 1846, 45 years after Ceres.  So, Ceres was briefly the eighth planet, then it wasn't, and then there were eight planets again when Neptune was discovered.

Ceres and Neptune, former and current "eighth planets", are now visible in the same region of the sky and shine at about the same brightness: magnitude 7.6 for Ceres and 7.8 for Neptune.

I was able to capture Ceres, Neptune, and Saturn in the same images with an Olympus E-M1iii camera and Sigma 30mm f/1.4 lens + softon filter.  The quarter moon was just setting behind the Bristol Head ridgeline, but was still an hour from official moonset, so the sky was bright with moon light.

Ceres: lower middle (circled), Neptune: upper middle (circled), bright Saturn.

 

Ceres (circled).

 

Neptune (circled) and bright Saturn.

Capella and the constellation Auriga in the northeast.

Capella is the sixth brightest star in the night sky, just slightly behind Vega.

The Pleiades over Snowshoe Mountain.

added 01 October:

The planet Uranus appears just to the lower right of the Pleiades:

Uranus (circled).

 Uranus was the first planet discovered in modern times, by William Herschel in 1781.  It is currently at magnitude 5.6, which technically makes it a naked-eye object under the right dark-sky conditions.  I could see it easily with a 1.8x40 wide-field binocular.

Two Crowns

 The constellation Corona Australis (Southern Crown) lies below Sagittarius and east of the Milky Way.  At the latitude of Creede it rides close to the southern horizon.

Corona Australis.  Lens: Sigma 56mm f/1.4 + softon filter.

 The constellation Corona Borealis (Northern Crown) is a well-known asterism in the northern sky.  At this time of year it can be seen above Arcturus in the west as twilight ends.

Corona Borealis.  Lens: Sigma 56mm + softon filter.

 

Arcturus (bottom center) setting behind Bristol Head.  Leica 9mm + sparkle filter.

Fomalhaut rising over Snowshoe Mountain.  Sigma 56mm.

Fomalhaut (Alpha Piscis Austrini) is the 18th brightest star in the night sky and is sometimes called the "Loneliest Star" because of its large separation from other bright stars.

The sky brightness this evening was a disappointing sqml=21.25.  Red airglow is very prominent in the raw photos.

Late at night with an old lens

 The Vivitar Series 1 135mm f/2.3 lens was introduced in the late seventies and was a well-regarded "third-party" lens.  The copy that I have was bought used and was manufactured in either 1978 or 1988, based on the serial number.  My best guess is that 1988 is the likely date, so 37 years old.  I coupled the lens with a Metabones Speedbooster, which converts the lens to 95 mm f/1.6.  

When used wide open this lens exhibits significant purple-fringing (longitudinal chromatic aberration) and some astigmatism in the corners.  Lens manufacturers of this era did not have available many of the exotic low-dispersion and high-index-of-refraction glass types that seem ubiquitous today.

The Pleiades rising over Snowshoe Mountain.

 

The Andromeda Galaxy (M31).

Mizar and Alcor (center left) descending toward Bristol Head.

Mizar and Alcor are the two components of a naked-eye double star in the handle of the Big Dipper.  

The Galactic Core setting behind the Bristol Head ridgeline.

 

Late night star shots

 Another clear night on Tuesday, sqml=21.3.  There were lightning flashes to the northeast from a distant storm.  

Equipment used: Olympus E-M1iii + Sigma 56mm f/1.4 + Hoya Softon filter, Sony A7iii + Sony FE 20mm f1/8 G + Hoya Sparkle-6 filter.

The Pleiades (M45) rising over Snowshoe Mountain.  Sigma 56mm.

 

Saturn and the Circlet of Pisces.  Sigma 56mm.

 

Neptune is still visible close to Saturn.  They will be keeping each other company for a while.  Neptune is currently 240.3 light minutes distant, about 3.4 times farther away than Saturn. Here is an expanded view:

 

MIrfak and the cluster Melotte 20.  Sigma 56mm.

 Mirfak (Alpha Persei) is the brightest member of Melotte 20, a loose association of about 100 stars also known as the Alpha Persei Moving Group.  Mirfak is slightly brighter than Polaris, the North Star.

 

The Double Cluster in Perseus.  Sigma 56mm

The Double Cluster (NGC 869 and NGC 884) in Perseus is an inspiring sight in small telescopes.

The Summer Triangle and Milky Way.  Sony 20mm

 This image of the Summer Triangle is a blend of two exposures, one with the Sparkle filter and one without.  This technique works well when there are no stationary foreground objects in the scene that would be blurred by the star tracking.

The southern and northern Milky Way.  Sony 20mm.

 There is strong green and purple airglow visible at low elevations both to the north and the south.

The Milky Way core setting behind Bristol Head. Sigma 56mm.

 

Twilight color

The end of Astronomical Twilight (dusk) is defined as the moment the center of the sun is 18° below the horizon.  At that time "Night" has officially begun.  Yesterday that moment occurred at 8:43 pm MDT and that is when the following sequence of images commenced.

 Equipment: Olympus E-M1iii + Leica 15mm f/1.7 + Hoya Sparkle-6 filter.

Arcturus over Bristol Head.

 In spite of being officially "Night", the camera still picks up a pink twilight glow.  There are reports of northern lights visible in Colorado last night (15 Sep), but this is a westerly view. Looking north, the pink glow merges with some green airglow.  Sky brightness was a mediocre sqml=21.25.

View to the north.

 

View to the south.

It may look like the neighbor's yard is lit up like a stadium, but that is just interior light spilling out and showing up on a long exposure (40 sec).

The Summer Triangle.

 The Summer Triangle (Altair, Deneb, Vega) was directly overhead.

Mid-September Milky Way

 The sky was finally clear on Sunday night after a long stretch of rainy weather.  In mid September the Milky Way is well past the meridian by the time twilight ends.  Measured sky-brightness to the east at 11 pm was sqml=21.35: good, but not great.  Green and purple airglow is evident in the 60-sec exposures.

Leica 15mm f/1.7, sparkle-6 filter.  11 pm MDT

 To the north, the Pleiades were rising over Snowshoe Mountain:

 The Great Square of Pegasus and the planet Saturn were high in the east:

 

credit: SkySafariAstronomy.com