The Lacework of Cygnus

Cygnus is perhaps the constellation of the Northern Hemisphere where the Milky Way is brightest, featuring a host of deep-sky objects. These objects are mostly made up of H-alpha nebulosity, i.e. hydrogen that is excited and ionized by nearby young stars. H-alpha-emitting hydrogen shines bright red at a wavelength of 656.3 nm. 


H-alpha features are mostly not visible to the human eye, unless a wide aperture telescope is used together with a special filter: and anyway their brightness is almost never sufficient to trigger color perception, so that they are seen glowing black and white, or in pale shades of light blue at most. Conversely, imaging these features with a CCD or CMOS camera and a selective filter that lets through only that precise wavelength will yield high-contrast photos showing all the tangles excited hydrogen makes up in the sky. 

Most astrophotographers focus on smaller regions of the Milky Way to image selected portions and details. However, wide-field work yields very esthetically pleasing results. A black and white camera coupled with a fast lens such as the Samyang 135 mm f/2 is a killer, portable lightweight rig that will never disappoint wide-field aficionados. 

Summer nights are quite short at mid-northern latitudes (around 45 degrees), affording not more than 3.5 hours of astronomical darkness in June. Luckily, a fast lens will make the most of these short nights.

On 12th June 2021 I went observing in the Alps at about 1700 elevation on a plateau called Piani dell’Avaro. I pointed my imaging rig consisting of a Moravian G2-8300 CCD camera, a Skywatcher EQ5 mount and a Samyang 135 mm f/2 lens at the heart of Cygnus constellation, i.e. around gamma Cygni (Sadr). I took a bit less than three hours’ worth of exposure time, which produced a deep exposure considering the relatively short integration time.

Below is the result in two flavors: a “traditional” version with some minor processing in PixInsight, and a starless version obtained in PixInsight using Starnet++. Starless images have become very popular lately, and while I am not a big fan of theirs, I concede that they make it possible to better  appreciate the faintest nebular structures, because the attention is somehow not “diverted” by the presence of the stars. Click on each picture to enlarge it and see all the relevant imaging details.

Wide-field Sadr region


Wide-field Sadr region (starless)


My imaging rig was controlled by a Raspberry Pi 4 Mini PC running Astroberry server, an astronomy-oriented Linux distro.

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