August marks the return of astronomical darkness and that also means a return to astrophotography, which inevitably draws us to objects within the Sagittarius Arm of the Milky Way that traverses the night sky at this time of the year.  As such there’s no shortage of targets but close to the zenith, high in the sky, it is difficult to avoid the wealth of possibilities that abound within Cygnus – the Swan.  I have often imaged favourites such as the North America Nebula and Veil Nebula but there is much, much more to Cygnus, in particular the vast area of nebulosity the stretches across the region centred around Deneb and Sadar (see red areas bekow).

Here I framed the image around the emission nebula SH2-115 but was unprepared and surprised by the richness of objects that the wider FOV captured.  Not far from Deneb, the large blue SH2-115 is energised by the open star cluster Berkley-90.  Numerous emission nebula from Lynds’ Catalogue of Bright Nebulae (LBN) can be seen adjacent to SH2-115 across much of the northern section of the image (see below).  Using the SHO Hubble palette format, here the nebulosity forms a rich golden-brown ribbon, which is exquisitely sculpted by the prevailing interstellar forces. 

South (right) of SH2-115 is SH2-112, a circular emission nebula thought to be energised by a blue double star BD + 45 3216 at the centre, with dark clouds and filaments contorted around the periphery.  Finally, just north-west of SH2-115 is the small but enigmatic SH2-116, AKA Abell 71.  This faint, blue disc was originally thought to be a planetary nebula, but this is now in doubt and awaits further research.

All-in-all there’s much to see in this busy image, which is an astrophotographer’s treasure trove of exciting objects, many of which are worthy of imaging in their own right; maybe I will return here again with a larger focal length one day? 

              

	IMAGING DETAILS
Object	SH2-115 + SH2-112 + SH2-116 (Abell 71) + various LBN
Constellation	Cygnus
Distance	<= 7,500 light-years
Size	Various + Abell 71 3.0 arc minutes
Apparent Magnitude	Various
Scope	William Optics GT81 + Focal Reducer FL 382mm  f4.72
Mount	SW AZ-EQ6 GT + EQASCOM computer control & Cartes du Ciel
Guiding	William Optics 50mm guide scope
	+ Starlight Xpress Lodestar X2 camera & PHD2 guiding
Camera	ZWO ASI294MM CMOS sensor
	FOV 2.87o x 1.96o Resolution 2.50”/pix  Max. image size 4,144 x 2,822 pix
EFW	ZWOx8 EFW & 31mm Chroma Ha, OIII, SII filters
Capture & Processing	Astro Photography Tool (APT), Deep Sky Stacker & PixInsight v1.8.9-2
Image Location              & Orientation	Centre = RA 20:34:32.40      DEC +46:42:37.408                         Left = North
Exposures	Ha x45 + OIII x42 + SII x43 x 300 sec Total Integration Time: 10hr 50 min
	@ Gain 139 & Offset 21 @ -15oC
Calibration	5 x 300 sec Darks  10 x  NB Flats & Dark Flats        @ ADU 32,000
Location & Darkness	Fairvale Observatory – Redhill – Surrey – UK    Typically Bortle 5-6
Date & Time	6th + 7th + 9th + 10th + 16th + 20th + 22nd August 2023 @ +22.00h
Weather	Approx. <23oC   RH >=60%                  🌙 <+63% Waning