Saturday, February 4, 2023

Winter Milky Way by Ralf Rohner


Winter Milky Way at a "Secret Beach" on the Oregon Coast © Ralf Rohner (click to enlarge) 

Nightscape photographers in the Northern Hemisphere often talk about the "Milky Way season", and bemoan that the season is "over" when winter comes. Actually, this is a misnomer. The Milky Way is always with us—summer or winter, as you can see in Ralf Rohner's beautiful panoramic view of the winter night sky.

What some less informed photographers are referring to is the absence of the "core" or galactic center of the Milky Way during the winter months. A better term might be: The "Milky Way core season" is over during the winter months. (The opposite is true in the Southern Hemisphere, when the core disappears below the horizon during some of their summer months).

"The Astrophotographer's Yin and Yang" at Mobius Arch © Ralf Rohner (click to enlarge)

This panoramic photo blend is a wonderful example of how our view of the Milky Way changes during the seasons. The photo is a blend of both Milky Way seasons, taken from the same location (Mobius Arch, in the Alabama Hills of eastern California). Ralf had this to say about the image:

Do you prefer winter or summer? Cold or warm? Dark or bright? Yin or Yang?

Yin is the dark side of our Milky Way, dominated by Orion, the hunter. As northern hemisphere dwellers, we associate this dimmer part of our galaxy with long, cold nights, but it also contains some of the most beautiful gems in the night sky, as the light fights its way back in the form of stunning red hydrogen emission nebulae, dotting the whole Milky Way band.

 For bright Yang, you have to look for Sagittarius, the steaming teapot, which points towards the galactic center, the brightest part of the Milky Way. In the northern hemisphere, this is associated with warmer but shorter spring and summer nights. Adjacent to the Milky Way core, in the border area of Scorpius and Ophiuchi, lies one of the most colorful parts of the night sky, the Rho Ophichui region. Despite all this light, one can not ignore the looming dark cloud of the Great Rift, blocking the starlight and colors in the constellations Serpens, Aquila and part of Cygnus. Ironically, this seemingly star-eating molecular cloud is home to some of the most active regions of star formation. The light once again gains the upper hand in the bright hydrogen emission nebulae of Cygnus, around the stars Sadr and Deneb.

 Thereafter, we enter the transition zone between the bright and the dark side, which is ruled by King Cepheus and his vain wife Cassiopeia.

 During a short period in spring and autumn, it is possible to see both sides in a single night. I had the privilege to be able to capture this at Mobius Arch in California.

The Yin-panorama was captured after nightfall, facing westward, and showing the winter Milky Way with setting Orion. The east facing Yang-panorama shows the rising galactic core and Cygnus, shortly before dawn. Both were merged to create this 'Yin-Yang' image, showing the entire Milky Way visible from mid northern latitudes. [The bright area in the sky, just to the right of the arch is Zodiacal Light.]

Ralf's technical information for the top photo of the "Secret Beach" will give you an idea of how he creates his nightscape panoramas:

  • Camera: Canon EOS-R, astro-modified 
  • Lens: Tamron 15-30mm f/2.8
  • Narrowband filter: IDAS NBZ filter
  • Tracker: iOptron SkyTracker Pro 
  • Sky: 6 panel panorama, each a stack of 6x 60s @ ISO1600 & 3 x 150s @ ISO6400 
  • Foreground: 6 panel panorama of 5s @ ISO400 during blue hour

Check out Ralf's informative blog on how to do landscape astrophotography.