Tag: iOptron Sky Tracker

Photographing the Milky Way and Cathedral Rock

We are entering Milky Way season—generally considered to be March through September in the northern hemisphere. In mid-March the Milky Way does not rise until well after midnight and the Galactic Center of the Milky Way is only about 25° degrees above the horizon by astronomical twilight.

The Milky Way and Galactic Center rise above Cathedral Rock. Venus and Mars are also visible just above the horizon and to the left of Cathedral Rock.
The Milky Way and Galactic Center rise above Cathedral Rock. Venus and Mars are also visible just above the horizon and to the left of Cathedral Rock.

Accompanying the Milky Way was the waxing crescent Moon which was 77% illuminated on the morning of 13 March 2022. The Moon would set around 0413 MST and twilight did not start until 0516 MST.

The Milky Way is lower in the sky and is combined with a foreground image containing star reflections in the small pool of water.
The Milky Way is lower in the sky and is combined with a foreground image containing star reflections in the small pool of water.

What this means is that I could photograph the landscape with the Moon illuminating it and then an hour or so later capture the Milky Way after the Moon had set and the sky was very dark.

I arrived with bright moonlight illuminating Cathedral Rock. I positioned the camera so that I could get some star reflections in the small—very small—pool of water. I also shot images without the water—just expanses of undulating red rock with alternating patterns of light and shadow.

Having finished that part of the show I had to wait until the Moon was at least a few degrees below the horizon allowing the sky to become very dark.

The Galactic Center of the Milky was about 16° above the horizon at moonset—which was just barely above the high point of Cathedral Rock. That wasn’t really the shot I wanted so I waited until it got higher.

Just before and after astronomical twilight the Galactic Center had risen to about 25° above the horizon. I shot a few images before twilight began to wash out the stars in the eastern sky. As a bonus, I was also able to capture the planets Venus and Mars just above the horizon.

The foreground images were shot at ISO 800, ƒ/5.6 and ƒ/8, and 120 seconds exposure with LENR (long exposure noise reduction) turned on. The star images were shot at ISO 800, ƒ/5.6, and 300 seconds exposure with LENR. Star images were taken with the camera mounted on an iOptron SkyTracker mount.

Revisiting the Rho Ophiuchi cloud complex

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Several years ago I took a sequence of images of the Rho Ophiuchi cloud complex and posted the result on these pages. As noted at the time I used a Nikon D700 paired with a Nikon 85mm ƒ/1.8 lens all mounted on an iOptron Sky Tracker. Images were stacked using Deep Sky Stacker and post processing was done using Photoshop CS6 and Astronomy Tools v1.6.

Rho Ophiuchi cloud complex
Rho Ophiuchi cloud complex

Since then I have been experimenting with different tools for postprocessing astro photos. Along the way I discovered some interesting software called rnc-color-stretch from Clarkvision.com.

The rnc-color-stretch algorithm does 3 main things. 1) Analyze the image histogram to maintain a black point or use set low level color throughout the stretching process. The histogram is analyzed at multiple stages from beginning to end. 2) A power stretch while maintaining the black point. 3) Recover lost color after the stretching process. How far you can stretch an image depends on the signal-to-noise ratio.

I’ve been testing this software on both recent and older images. I thought it might be interesting to try it on the Rho Ophiuchi images taken in 2015. Once again, I used Deep Sky Stacker to register and align the images. Then I ran rnc-color-stretch. The result is the image shown above. I thnk it did a fine job of pulling out the details and the color.

Milky Way, Moon, and Mercury

It’s that time of year when the Milky Way is visible through much of the night. It is best observed when there is no Moon in the sky—and from very dark skies away from areas of light pollution. I wanted to capture both the Milky Way in a very dark sky and to capture Moonlight gently lighting up the still partially snow-covered mountains. So I headed out to Kendrick Park for some midnight sky photography.

The Milky Way rises above the San Francisco Peaks in northern Arizona.
The Milky Way rises above the San Francisco Peaks in northern Arizona.

The result is this composite of two images. The first was taken of the San Francisco Peaks as the moon was low in the west at around 1118 MST. This was a bit more than an hour before moonset (0030 MST). An exposure of 300 seconds at ISO 800 and an aperture of f/8 was used.

The second image was taken at 0047 MST shortly after the moon had set allowing the fainter stars in the night sky to appear. This image was also 300 seconds at ISO 800 and an aperture of f/5.6. To prevent streaking of the stars an iOptron Sky Tracker was used. The two images were then blended together.

This is similar to images taken in the past of Cathedral Rock and Wukoki Pueblo with the Milky Way rising above. Also present low in the photograph is airglow (or nightglow).

Last week the two-day old crescent Moon (only 3.7% directly illuminated) provided a photo opportunity as it set over Upper Lake Mary. During the months of May, June, and July, the thin crescent Moon lines up with the long axis of Upper Lake Mary. This results in nice reflections of the Moon on the waters of the lake—but only if there is little or no wind. A bonus this month was the small planet Mercury was also setting in the northwest.

A thin crescent Moon throws a large reflection in Lake Mary, Flagstaff, Arizona.
A thin crescent Moon throws a large reflection in Lake Mary, Flagstaff, Arizona.

The image also shows the unlit part of the crescent Moon illuminated with Earthshine, also known as Da Vinci Glow. Yes, that Leonardo Da Vinci. Mercury can be seen just above the treetops on the far right side of the image.