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.