Dark sky, bright Milky Way

 The 10-pm sky on 28 July was darker than average with a measured value of sqml=21.73 mpsas.   These images were obtained with a Sony A7iii camera and a Rokinon AF 35mm f/1.8 lens, ISO 1600, 30 s.

Milky Way core. Hoya Sparkle-6 filter.

Hoya Softon-A filter.

Softon filter.

There are current predictions of aurora visibility at middle latitudes.  Nothing was visible last night to the unaided eye.  The Bristol Head ridgeline was silhouetted against some kind of background glow, but it could be just normal airglow.

Big Dipper over Bristol Head.  Softon filter.

 

The Milky Way returns

 It was always there, just hidden until now by the bright moon, storm clouds, and wildfire haze.  Last night (27 July) was mostly clear with only a few clouds drifting by near the horizon.  The measured sky brightness at 10 pm was sqml=21.55, which is respectably dark.

The following images were obtained with an Olympus E-M5iii camera and 17mm f/1.8 lens, ISO 1600, 60 s.

The core of the Milky Way looms over the southern flank of Snowshow Mountain:

no filter

A diffusion filter helps to emphasize the relative brightness of individual stars and better reveals the constellation patterns:

Hoya Softon filter

A slightly different composition includes the glow of interior lights from neighborhood cabins and some distant clouds on the horizon lit up by heat lightning.

Hoya Sparkle-6 filter

Morning sun, 27 July

Some solar flares have been causing shortwave radio blackouts.  The following images show the responsible sunspot groups.  These images were taken early (8:40 am MDT).  The sky was later covered by storm clouds for much of the day.

The telescope was an Astro-Tech AT102ED f/7 refractor with a Lunt solar wedge.  The camera was an Olympus E-M5iii with a ND-0.6 filter, ISO 200, 1/1250 s.

 

Drifting clouds and rising Buck Moon

The full moon of July is traditionally known as the "Buck Moon".  This year the full moon occurred on the morning of 21 July.  That evening some drifting clouds gave hints about  where the moon would rise over the shoulder of Snowshoe Mountain.

All photos were obtained with an Olympus E-P5 and Canon FD 300mm f/4L lens.

The Sun yesterday

 The Sun imaged with a Lunt LS50THa double-stacked Hydrogen-Alpha telescope and a ZWO ASI178mm camera:

19 July 2024

The white patches are called plages and are hotter-than-average areas around sunspots.  The grey linear features are called filaments and are prominences seen in silhouette against the solar disk.  Around the edge are more prominences.

 

Moon and stars and clouds

 Wednesday night (17 July) was mostly clear with a few wispy clouds.  The 11.4-d moon was rising over Snowshoe Mountain's southern flank.

A couple hours later this image of the waxing gibbous moon was obtained with the 6" f/5 reflector:

17 July. E-M5iii, ISO 400, 1/800 s.

In spite of the bright moonlight, the Big Dipper was easily visible with some clouds drifting by underneath:

E-M1iii + Panasonic 20mm f/1.7 + softon filter.  ISO 1600, 30 s.

The second star from the end of the Big Dipper's handle is the naked-eye double star Mizar and Alcor:

A closer look with the 6" reflector reveals that Mizar (left bottom) is itself a visual double star:

E-M5iii.  ISO 1600, 1/10 s.

Both stars of the Mizar pair and Alcor (upper right) are doubles themselves, which makes this a six-star system.  The fourth star in the upper left is just a distant background star.

The 10.4-d moon on Tuesday night was visible between a break in the clouds:

16 July. ISO 200, 1/640 s.

Something new and different: photography with a 6-inch reflector

 The waxing moon is lighting up the sky when the rain clouds aren't obscuring it.  This is not the time for wide-field astrophotography.

Last night (Friday 12 July) the late-night sky was clear, so I decided to try out a telescope that has been unfairly neglected: a 6-inch (150 mm) f/5 Newtonian reflector.  This is a superb telescope for visually scanning the star clusters and nebulas ("nebulae" for the overly pedantic) of the Milky Way, but I have never used it photographically.  

During the day I prepared a motorized equatorial mount that would be suitable for carrying this telescope.  But that mount is heavy and requires some effort to set up and balance, so I decided instead to first try some test images with a much lighter non-tracking alt-az mount.  It turns out that the simpler mount was all that was needed for doing short (< 0.1 sec) exposures.

Here is a picture of the telescope and mount:

The 6.7-d moon was a good first test subject:

E-M5iii. ISO 400, 1/640 s.

The primary photographic goal was the double star Albireo (Beta Cygni).  Albireo is a double star in the constellation Cygnus (The Swan).  It is famous for its appearance in small telescopes.  The two components are separated by 35 arcsec and have contrasting colors of golden orange and sapphire blue.  Albireo is located at the bottom of the "Northern Cross", or in traditional constellation art, at the head of the Swan.

Constellation Cygnus. credit: IAU

I have imaged Albireo several times before with smaller-aperture optics and it is easy to separate the two stars.  The trick is to get an exposure that also also displays the colors. My hope was that the natural diffraction pattern of the Newtonian secondary-mirror holder would spread out the light of the two stars enough to prevent the colors from overexposing and washing out.  Here is an image of the bright star Vega that shows the four-spike diffraction pattern:

Vega, ISO 1600, 1/10 s, untracked.

The image of Albireo was successful, even though the diffraction pattern is not seen, and probably had little effect:

Albireo (Beta Cygni), ISO 1600, 1/10 s, untracked.

The trial images with the alt-az mount were so successful that it was not necessary to haul out the heavier equatorial mount.  This is my best image yet of Albireo that shows that contrasting colors of the two stars.

There has been a long-standing debate about whether the two stars are gravitationally bound to each other or just a chance optical alignment.  The current consensus is that the two stars are not connected and just a chance alignment.

Three nights around the new moon

 The new moon was on July 5.  These images were obtained on the three nights bracketing that event.

In this image the Small Sagittarius Star Cloud is above left center.  The Lagoon Nebula (M8) is below center right.  There are many objects of interest in this section of the Milky Way.  An impressive neighborhood fireworks display was in progress behind me during this photo session.  The sky was slightly darker than usual at sqml=21.65 mpsas (between fireworks detonations).

4 July. E-M1iii + Sigma 56mm f/1.4 + Softon filter.  ISO 1600, 30 s.

The sky was somewhat brighter the next night (5 July), at 21.45 mpsas. The camera revealed green and red airglow near the horizon in all directions.  This natural luminescence provides a nice silhouette of the surrounding mountains.

Arcturus over Bristol Head, 5 July.  Sony A7iii + Laowa 15mm f/2 + Softon filter.

 

Milky Way 5 July.  Sony A7iii  + Laowa 15mm f/2 + Sparkle-6 filter.

Milky Way over McCall Gulch, 5 July.  Laowa 15mm + Sparkle-6 filter.

The Double Cluster was low in the north on Saturday night, 6 July.  In this image it is just 8 deg above the distant La Garitas and submerged in murky airglow.

Sony A7iii + Rokinon 85mm f/1.4 AFII.  ISO 1600, 30 s.

The star clusters M7 and M6 are just right of center in this image:

Rokinon 85mm f/1.4 AFII.

6 July, 11:30 pm MDT. Rokinon 24mm AF f/1.8 + Sparkle-6 filter.

Galactic center rising. Testing a new lens.

 The new lens is a Rokinon (Samyang) 85mm f/1.4 AF Series II for Sony E mount.  It is one of several variants that are successors to the original manual-focus Rokinon 85mm f/1.4 Aspherical.  This older lens comprises nine elements, one of which is aspherical.  My copy was purchased in 2011 with a Nikon F mount.  The new lens has eleven elements, five of which are HR (High-Refractive Index) and one ED (Extra-low Dispersion).

I have had good results with the old lens, but it does show pronounced purple fringing (Longitudinal Chromatic Aberration) in astro photos .  This can be mitigated somewhat in post-processing, for example by using the "Defringe" option in Affinity Photo.  My hope was that the updated optical design would reduce the purple fringing and eliminate the need for software remediation. This turned out to be correct.  The corner astigmatism is also about half as much as seen with the old lens.  Another win.

The sky brightness at 11pm was sqml=21.6, which is nicely dark.  Even better, there were no outside lights glaring from neighbor's cabins.

The following images were taken with a Sony A7iii camera, ISO 1600, 30 s. 

Milky Way rising over Snowshoe Mt.  New 85mm lens (AF II), f/1.4.

Old 85mm lens (Aspherical), f/1.4.

There was some variable green airglow between these two images, which were seven minutes apart.  All of those dark patches and filigree are galactic dust clouds in the next spiral arm between us and the center of the galaxy.

The center of the galaxy has a supermassive black hole with a mass of about 4 million suns.  It is a radio source known as Sgr A*.  It is invisible in normal light, but can be studied at infrared and radio wavelengths.  The location is marked with a white circle in the next image.

The white circle marks the galaxy center.  New 85mm lens, f/1.8.

85mm f/1.4: Old manual focus (left) vs New AF (right)

 

Midnight Milky Way and neighborhood lights

 When I checked the sky at 10pm on Tuesday night there were substantial clouds moving through the southern sky.  An hour later the clouds were gone except for a few lingering dark patches in the north.  The sky was dark, sqml=21.6, except for one problem: a neighbor on the hill to the south had a bright gable light burning.  After some scouting around the property, I found a spot on the back driveway where the hay shed would block the direct line-of-sight to the offending light and still give me a view in the directions I wanted.

Sony A7iii + Sony FE 20mm f/1.8, Hoya Sparkle-6 filter.  ISO 1600, 30 s.

Many dedicated astrophotographers travel to exotic locations to get Milky-Way photos with alpine lakes and glaciers or African trees as foreground objects.  And their photos are fantastic.  I am not that dedicated, however, so what you get here is a photo with the hay shed, horse trailer, and Chevy truck as foreground.

As before.  Vertical orientation.

Looking west, Arcturus was descending toward Bristol Head.  Arcturus is the fourth brightest star in the sky and the brightest in the North Celestial Hemisphere.  Bristol Head is silhouetted against green and red airglow.

The primary objective of this photography session was to capture images of asteroid (249) Ilse (current magnitude 14.5) (and successful).  For these I used a Rokinon 135mm f/2 lens and E-M5iii camera. Here are a couple images captured with the same setup:

The Coathanger cluster.  ISO 1600, 60 s, Kase Astroblast filter. 5.5-deg FOV.

Sadr, Gamma Cygni.

Gamma Cygni, or Sadr, is the star at the center of the "Northern Cross" in the constellation Cygnus.  In the image above, North is to the left.  Sadr is a foreground star to the red nebulosity and not physically connected.

Here is a finder chart showing the location of this image:

Credit: SkySafariAstronomy.com