OBSERVER’S CHALLENGE* – SEPTEMBER, 2020
by Glenn Chaple
Veil Nebula – Supernova Remnant in Cygnus (Mag: 6.9, Size: 3.5° X 2.7°)
A few degrees south and slightly east of the 2nd magnitude star epsilon (ε) Cygni is a large wreath-shaped nebula known as the Cygnus Loop. Two of the Loop’s brightest portions form what is more commonly known as the Veil Nebula.
William Herschel discovered the eastern part of the Veil on the evening of September 5, 1784 and captured its westerly partner two nights later. He catalogued them as H14⁵ and H15⁵ - the 14th and 15th of his Class 5 (Very Large Nebulae) objects. Today, they are identified by the New General Catalog designations NGC 6992/5 and NGC 6960, respectively.
The best way to find the Veil Nebula is to arm your scope with a low-power, wide-field eyepiece and point it towards the 4th magnitude star 52 Cygni. This yellow-orange K-type giant is a foreground star that lies near the center of the western Veil. Once you’ve spotted it, continue peering into the eyepiece as you gently nudge your scope about 3 degrees eastward and slightly north. The eastern Veil should come into view. Both portions of the Veil Nebula may be glimpsed with small-aperture scopes from dark sky areas. During the 1981 Stellafane Convention in Springfield, VT, I captured the western Veil with a 3-inch f/10 reflector and both eastern and western Veils with a 4 1/8-inch f/4.2 RFT (Edmund Astroscan).
More recently, I viewed the Veil from my backyard in suburban north-central Massachusetts (limiting magnitude 5.5). It was barely visible with a 4½-inch f/8 reflector and still faint through a 10-inch f/5 reflector. Both scopes needed an assist from an O-III filter and (even better) an Orion UltraBlock narrowband filter.
The Veil Nebula presents a variety of Observer’s Challenges. It is said to be visible with the unaided eye with the help of an O-III filter and extremely dark skies. In his book Cosmic Challenge, Phil Harrington reports seeing the eastern Veil and (with difficulty!) the western Veil with 10X50 binoculars. Can you match these feats? Again, don’t bother trying if you live in a light-polluted area. Owners of small-aperture scopes are encouraged to try their luck with the Veil. Having seen it with my 3-inch reflector, I’m going to challenge my observing skills by tackling it with a 60mm (2.4-inch) refractor. Mario Motta’s close-up images of the eastern and western Veil reveal their complex filamentary structure. Can you capture this visually with a medium to large aperture scope?
Three portions of the Cygnus Loop not mentioned in this article are Pickering’s Triangle, located a degree northeast of the western Veil, and NGC 6974 and NGC 6979, the most northerly portions of the Cygnus Loop. All appear in the accompanying wide-field image of the Cygnus Loop, taken by Doug Paul. What size telescope (and which filter) will give you a visual sighting?
The Cygnus Loop is a supernova remnant, the result of a supermassive star that suffered an explosive death some 5,000 to 10,000 years ago. Recent GAIA parallax measurements of stars imbedded in the Cygnus Loop gases indicate a distance of 2400 light years, suggesting a true diameter of 130 light years.
*The purpose of the Observer’s Challenge is to encourage the pursuit of visual observing. It is open to everyone who is interested. If you’d like to contribute notes, drawings, or photographs, we’ll be happy to include them in our monthly summary. Submit your observing notes, sketches, and/or images to Roger Ivester (firstname.lastname@example.org). To find out more about the Observer’s Challenge or access past reports, log on to rogerivester.com/category/observers-challenge-reports.
Finder Chart for the Veil Nebula
(Stellarium and Sky and Telescope)
Images of the Veil Nebula
Cygnus Loop Image by Doug Paul (ATMoB) taken with Canon 6D, 400mm f/2.8 (143mm (5.6 inch) aperture), ISO 1600, 51 subs x 2 min = 1.7 hr total exposure, 1/4 scale. North is up.
(L) Veil Nebula East (NGC 6992/5) (R) Veil Nebula West (NGC 6960) Images by Mario Motta, MD (ATMoB) taken with 8-inch F/8 RC; Veil East, 1.5 hours Ha, 1 hour each S2 and O3 filters; Veil West, 1 hour each of Ha, and O2, and 30 min S3 filters. North is up.
(L) Veil Nebula East, as seen with 3-inch f/10 reflector at 30X (R) Veil Nebula West, as seen with 10-inch f/5 reflector at 48X. Sketches by Glenn Chaple (ATMoB)