Starscapes by moonlight

 Last night the moon was 8.9 days old (time since new moon) and 66% illuminated.  The bright moonlight presents a challenge for normal astrophotography. However, it also provides an opportunity for some interesting starscapes because the surrounding landscape is lit up while the stars are visible.

Capella setting over Bristol Head:

Sony A7iii + Rokinon 85mm f/1.4 @ f/2.8 + softon filter.  ISO 800, 20 s.

Sony A7iii + Rokinon 85mm f/1.4 @ f/2.8 + sparkle-6 filter.  ISO 800, 20 s.

Capella is the sixth brightest star in the sky with a magnitude of 0.1.  The only brighter stars visible from Creede are Sirius, Arcturus, and Vega.

The sparkle filter is really too strong to use at this focal length.  It works better with focal lengths of about 30mm and shorter. However, because of the way it spreads out the light it does a remarkable job of preserving star colors.  The red star top center is Pi Aurigae, a red giant star.  The color is much more obvious with the sparkle filter than the softon filter. 

Turning south, it was possible to see the giant globular cluster Omega Centauri gliding along above Piedra Peak.  Omega Centauri has about 10 million stars and contains about the same mass as the supermassive black hole at the center of our galaxy.

 

Olympus E-M5iii + Canon FD 300mm f/4L + Metabones speedbooster.  ISO 1600, 20 s.  Effective focal length = 213 mm f/2.8.

Toward the southeast, Antares and the constellation Scorpius were rising above the southern flank of Snowshoe Mountain.  Antares is the orange star left of center.  The globular cluster M4 is right of center.  Antares is the 15th brightest star. M4 contains about 100,000 stars and is the closest globular cluster to earth (about 6000 ly).

Canon FD 300mm f/4L + Metabones speedbooster.  ISO 1600, 30 s.

Three globular clusters captured last night with the Canon FD 300mm:

M13 (left), M4 (center), Omega Centauri (right). 1-deg FOV.

The background in the M13 image is much darker because it was opposite from the moon, where the sky was darker.

Aurora over Creede

An unusually strong solar storm hit the Earth on Friday May 10 causing auroras that were seen as far south as Puerto Rico.  The storm is apparently persisting through this weekend.  It has been cloudy and snowy here in Creede, but there was a brief thinning of the clouds last night (Saturday).  

11 May.  Sony A7iii + Laowa 15mm f/2 + sparkle-6 filter.

  That is what the camera saw (ISO 1600, 30 s), but I could not detect the glow with my unaided eyes.  The north star Polaris is in the center of the frame, the Big Dipper at the top.

Three-frame animation.  30 s exposures.

 

The Little  Dipper through auroral glow.  Laowa 15mm f/2 + sparkle-6 filter.

credit: SkySafariAstronomy.com

Omega Centauri

 Omega Centauri is the name of a globular cluster in the southern constellation Centaurus.  This cluster is the largest globular cluster in our Milky Way Galaxy.  The number of stars (about 10 million), the mass (about 4 million solar masses), and the spectral distribution of stars support the hypothesis that this cluster is the remnant core of a dwarf galaxy captured by the Milky Way.

With a declination of -47.6° this cluster never rises more than 4.6° above the (sea-level) horizon at the latitude of Creede (37.8°).  This is a problem, because our local horizon is mostly obscured by the surrounding mountain peaks and ridges.  From my backyard observing location the view is blocked by the southern flank of Snowshoe Mountain and a neighbor's cabin.  From the front yard, however, there is a view south toward Piedra Peak where I can watch this cluster glide just a couple degrees above the distant peaks.

Omega Centauri emerging from the southern flank of Snowshoe Mt, 08 May, 11:23pm MDT.

 

 This image was obtained with a Canon FD 300mm f/4L lens and an Olympus E-M1iii camera (ISO 1600, 20 s) just as the cluster was transiting the meridian, its highest point in the sky.  The sky brightness (near the zenith) was sqml=21.48.

Here is a closer look with a 1° field-of-view (ISO 1600, 60s):

Omega Centauri.  E-M1iii + Canon FD 300mm f/4L. 2x binning.

Omega Centauri is an impressive sight in a small telescope or even binoculars. Here is a comparison to the "Great Hercules Cluster", M13:

M13 (left) and Omega Centauri (right).  Canon FD 300mm f/4L.

The Hercules cluster M13 has about 500,000 stars, or roughly 1/20 as many as Omega Centauri.  An interesting fact is that the total mass of all the stars in Omega Centauri is nearly the same as the mass of the supermassive black hole at the center of our galaxy. The Milky Way's central black hole has a radius less than half of the orbit of Mercury, while Omega Centauri spans about 150 ly.

Two years ago a waxing crescent moon lit up the sky as Omega Centauri emerged from behind Snowshoe Mountain.  In the image below the silhouette of Piedra Peak is in the lower right corner, the bright rectangle near the bottom is a neighbor's cabin window.

02 June 2022.  E-M5iii + Rokinon 135mm f/2.  ISO 1600, 60 s.

A comparison with the crescent moon that was setting over the flank of Bristol Head shows the relative size of this cluster:

Omega Centauri and the Moon.  E-M5iii + Rokinon 135mm.  02 June 2022.

When the faintest stars of the cluster are accounted for it has an angular diameter slightly larger than the moon.

Somewhat higher in the sky from Omega Centauri is the barred-spiral galaxy M83:

M83.  Canon FD 300mm f/4L.  1-deg FOV.  ISO 1600, 60 s.

 M83 is known as the "Southern Pinwheel Galaxy." Here is a finder chart:

 

credit: SkySafariAstronomy.com

Sirius setting over Bristol Head

 Sirius is the brightest star in the sky and rules the night in the northern-hemisphere winter.  As spring advances toward summer it hangs low in the SW.

This image was a 1-sec exposure (ISO 1600) using a Tokina AT-X 100-300mm f/4 zoom with a Metabones Speedbooster.  The effective focal length was 213 mm at f/2.8.

Sirius

Later in the evening I was evaluating a different lens, a Canon FD 300mm f/4L.  The following image is the great globular cluster M13 in the constellation Hercules.  Hercules rises in the NE in the late evening.  The sky brightness was sqml=21.68.

M13, 2° FOV.  E-M1iii + Canon FD 300mm f/4L.  ISO 1600, 60 s.

This lens is also superb for daytime use.  These early-morning elk were about 1 km away on the hillside across the Rio Grande:

 

Fresh snow on Bristol Head, 06 May

The Big and Little Dipper

 This time of year the two asterisms known as the Big Dipper and Little Dipper stand high in the northern sky.  These two star patterns are part of the formal constellations Ursa Major and Ursa Minor.

Sony A7iii + Laowa 15mm f/2 + Softon filter.  ISO 1600, 30 s.

Little Dipper.  Hoya Softon filter.

Sony A7iii + Laowa 15mm f/2 + Sparkle-6x filter.  ISO 1600, 30 s.

Little Dipper.  Hoya Sparkle-6x filter.

I like both of these two filters.  The Softon filter gives the stars a more natural appearance.  The Sparkle-6 filter results in a more artistic flair.

For those not familiar with these star patterns, here is a finder chart:

credit: SkySafariAstronomy.com

The sky brightness when these images were obtained was sqml=21.69 mpsas.  See the previous post for an explanation of this number.

Zodiacal light over Bristol Head

 The dark skies of Creede are a welcome change from the urban murkiness of Santa Fe.  Last night the measured sky brightness here was sqml=21.69*, which is very dark indeed. There were some clouds still skating across the sky, but a brief opening provided a view of the Zodiacal light over Bristol Head.  The Zodiacal Light is a diffuse glow caused by sunlight scattering from dust particles in Earth's orbital plane.  Most of the dust is believed to originate from Mars.

Sony A7iii + Sony FE 20mm f/1.8 G + softon filter.  ISO 1600, 30 s

The yellow line in the chart below represents the Ecliptic, Earth's orbital plane.

credit: SkySafariAstronomy.com

The following night, an hour earlier:

Sony A7iii + 20mm f/1.8 G + sparkle-6 filter.  ISO1600, 30 s.

Big Dipper

 *Sky brightness is measured in units of magnitude per square arcsec (mag/arsec²) or MPSAS.  A device called the Sky Quality Meter-L (sqml) manufactured by the company Unihedron is used to measure this quantity.   

More double stars, with the Celestron C6

 The previous double-star results with the Sky-Watcher Skymax 102 MCT were sufficiently pleasing that I decided to try some more-challenging targets with a larger telescope, the Celestron C6 SCT (Schmidt-Cassegrain Telescope).  The nominal focal length (1500 mm) of this scope was increased to 3750 mm with a Tele Vue 2.5x Powermate.  Combined with the 0.0033-mm pixel size of the E-M5iii camera this yields an image scale of 0.18 arcsec/pixel.

Here is a list of the double stars and their nominal separations in arcseconds:

• Izar (Epsilon Boötis) : 2.9"
• Mizar (Zeta Ursae Majoris) : 14.4"
• Pi Boötis : 5.5"
• Xi Boötis : 4.8"
• Rigel (Beta Orionis) : 9.5"
• Porrima (Gamma Virginis) : 3.4"

Izar is the closest pair in this set and was initially difficult visually, until I realized that the collimation of the scope needed to be tweaked.  After a fairly small adjustment it became easy to separate with the bluish secondary appearing as a tiny pinprick next to the yellowish primary.  It is hard to capture that view with the camera because atmospheric turbulence blurs the image.  Most of these images were taken with a shutter speed of 1/4–1/2 s at ISO 1600 and are stacks of 2–4 of the sharpest separate exposures.

Here is a finder chart showing the location of the three double stars in the constellation Boötes:

credit: SkySafariAstronomy.com

Celestron C6

As usual, click on an image to get to the larger version.

The Christmas Comet of 2018

 Comet 46P/Wirtanen is a periodic comet discovered in 1948.  It orbits the sun with a period of 5.4 years with a distance varying  between 1.05 AU and 5.17 AU (1 AU = radius of Earth's orbit).  In 2018 it made an unusually close approach to Earth (about 7 million miles) on 16 December and achieved naked-eye visibility (magnitude 4).  It was the brightest comet of 2018 and was dubbed the "Christmas Comet" by some news sites.  

During the close approach it was possible to detect  the comet's motion over a period of less than ten minutes.  I did not record the lens I used for these photographs.

Comet 46P/Wirtanen near the Pleiades, 16 Dec 2018.  E-M5, ISO 800, 15 s.

8-min interval.  Comet is moving right to left.

Through the clouds. 15 December 2018.

15 December 2018

14 December 2018

13 December 2018

11 December 2018

Some of these images are corrected for purple-fringing (a common flaw with old lenses), some are not.  The brighter stars stand out better in the non-corrected images.

The 2024 solar eclipse seen from Santa Fe

The day started cloudy and mostly stayed cloudy, but the clouds were thin enough at times to get a view of the partial eclipse from Santa Fe.  An Orion 80mmED f/7.5 refractor was used for photography.  This telescope was riding on a Celestron CG-4 motor-driven equatorial mount.  The camera was an Olympus E-M5iii looking through a ND-0.6 filter and a Lunt solar wedge.  For visual observation we used a Celestron  80mm f/5 refractor equipped with a front-mounted Kendrick Al-mylar solar filter.  A black-polymer "window frame" filter was used for non-telescopic viewing.

A few minutes before maximum eclipse (12:30 MDT).

 The variable and at-times thick clouds disrupted the planned-interval exposures, so I pretty much clicked away at random in case the clouds got worse.

This false-color nine-image montage spans about 45 minutes:

The bottom-left image is near maximum eclipse.

This is a natural-color animation created from all the images:

There were occasional moments of relative clarity:

Sun spots.  ISO 200, 1/200 s.

ISO 200, 1/640 s.

This is a view through the black-polymer window-frame filter using a Nikon 85mm lens on a Sony A7iii camera:

Comet 12P/Pons-Brooks

 Comet 12P/Pons-Brooks is a short-period "Halley-type" comet that was discovered in 1812.  It has an orbital period of 71 years.  It is currently visible with binoculars low in the western sky during twilight. 

Catching the comet photographically from my back-yard location in urban Santa Fe is very challenging because of trees, walls, and electrical wires.  By the time twilight has faded enough to get good exposures the comet has been obscured by all the neighborhood clutter.  

Here is the way it looked at 8:30 pm tonight:

E-M5 + Rokinon 135mm f/2.  ISO 800, 20 s.

This is a stack of three 20-sec exposures, with some contrast enhancement:

E-M5 + Rokinon 135mm f/2.  ISO 800, (20 s × 3).  3° × 2° FOV.

A quick Google search reveals that it is being called the "Devil" comet, the "Horned" comet, the "Mother-of-Dragons" comet, the "Once-in-a-lifetime" comet, and probably some other eye-rolling names.   Visually, it's just a fairly ordinary comet.   There are, however, some very beautiful long-exposure photos showing up on the internet.

La Superba -- Y CVn

 Another star of interest in the constellation Canes Venatici is "La Superba", Y Canus Venaticorum or Y CVn.  It is one of the reddest stars in the sky.  It belongs to a class of stars called "Carbon Stars".  These stars have large amounts of carbon compounds in their atmosphere which absorb short wavelengths.  The name was coined by the 19th-century astronomer priest Angelo Secchi.

credit: SkySafariAstronomy.com

La Superba.  E-M5 + Rokinon 135mm f/2.  ISO 800, 30 s.  2° FOV.

E-M5iii + AT72mmEDII.  ISO 1600, 10 s.  0.5° FOV.

E-M1iii + Tokina AT-X 80-200mm f/2.8 @ 200mm + softon filter.  ISO 1600, 30 s.

This last image shows the red color best.  The lens is an old Nikon-mount manual-focus zoom adapted to the micro-four-thirds E-M1iii.  Sky brightness was sqml=19.62.