The Veil Nebula In Cygnus – September 2020 Observer’s Challenge Report #140

“Work-File” Report:  For organization only.  The following are all participants to-date.  The cut-off date for submissions is the 8th of the following month, and we try to issue the final report by the 10th.  

MONTHLY OBSERVER’S CHALLENGE

Compiled by:

Roger Ivester, North Carolina 

&

Sue French, New York

September 2020

Report #140 

The Veil Nebula In Cygnus  

Sharing Observations and Bringing Amateur Astronomers Together

Introduction

The purpose of the Observer’s Challenge is to encourage the pursuit of visual observing. It’s open to everyone who’s interested, and if you’re able to contribute notes, and/or drawings, we’ll be happy to include them in our monthly summary. Visual astronomy depends on what’s seen through the eyepiece. Not only does it satisfy an innate curiosity, but it allows the visual observer to discover the beauty and the wonderment of the night sky. Before photography, all observations depended on what astronomers saw in the eyepiece, and how they recorded their observations. This was done through notes and drawings, and that’s the tradition we’re stressing in the Observer’s Challenge. And for folks with an interest in astrophotography, your digital images and notes are just as welcome. The hope is that you’ll read through these reports and become inspired to take more time at the eyepiece, study each object, and look for those subtle details that you might never have noticed before.

This month’s target

The Veil Nebula has long been modeled as the remnant of a supernova explosion that occurred within an interstellar cavity created by the progenitor star. However, a recent study by Fesen, Weil, and Cisneros (2018MNRAS.481.1786F ) using multi-wavelength emission maps indicates that the large-scale structure of the Veil Nebula is due to interaction of the remnant with local interstellar clouds. Employing Gaia DR2 data, the team determined an distance of 735±25 pc. 

This beautiful nebula bears several NGC designations. Its western arc, NGC 6960, runs through the naked-eye star 52 Cygni and is commonly called the Witch’s Broom. The tantalizingly intricate western arc is called NGC 6992 in the north, while the tattered southern reaches comprise NGC 6995. The brightest part of Pickering’s Triangular Wisp, which claims no NGC number, lies between the northern tips of the two great arcs. The discoverers of NGC 6974 (Lord Rosse) and NGC 6979 (William Herschel) gave these pieces positions that don’t correspond to anything obvious, but the names have been popularly tagged onto the northern and southern parts of the nebulosity just east of Pickering’s Triangular Wisp. As good a guess as any.

Maria Motta:  Observer from Massachusetts

Veil Nebula East…Maria Motta

1.5 hours Ha, 1 hour each S2 and O3 filters, through my 8-inch RC f/8 for wide field.  Processed Pixinsight. Very colorful because the three elements are separated very well in separate shock fronts.

NGC 6960 (western veil), taken through my 8-inch RC, 1 hour each of Ha, and O2, and 30 min S3 filters (clouds came in for the end of the S3:(processed PixInsight)

Pickering’s Triangle

James Dire: Observer from Illinois

The Veil Nebula, sometimes called the Great Cygnus Loop, is the remnant of a supernova (exploding star) that occurred sometime between 5000 and 8000 years ago.  The explosion remnants are estimated to be 2400 light years away. The Veil is an emission nebula of hot glowing gasses, mostly hydrogen, which have not yet expanded and cooled sufficiently to dissipate. The supernova remnant is identified by five NGC numbers: 6960, 6974, 6979, 6992 and 6995. The entire complex spans a distance equivalent to six times the diameter of the Moon.  William Herschel discovered the Veil Nebula in 1984, but parts of the nebula complex were cataloged by his son John in 1828 and Lawrence Parsons in 1873.

NGC 6960 is the Western Veil Nebula or Network Nebula.  This arc is nearly two degrees long and 0.1 degrees wide.  The brightest section is adjacent to the star 52 Cygni, a magnitude 4.2 star.  52 Cygni is a double star with components of magnitude 4.2 and 8.7 separated by 6.4 arc seconds. The star is just in front of the leading edge of Cygnus the Swan’s eastern wing, or 3.25 degrees south of the star Gienah (Epsilon Cygni), a 2.5 magnitude star that marks the center of said wing.  Gienah is also the southeastern star making up the Northern Cross asterism. Finding Gienah, then 52 Cygni makes finding the Western Veil easy!

The Eastern Veil Nebula goes by both NGC 6992 and 6995.  It is also known as the Filamentary Nebula.  The north side of the arc is visually brighter and more compact (NGC 6992), while the southern portion extends into myriad filaments (NGC 6995).

The northern potion of the nebula is split between NGC 6974 and 6979.  These sections are not as bright as the Eastern and Western Veil sections, but they are not beyond the means of larger amateur light buckets.  I have seen them in a 14-inch Newtonian.

About one-third the way between the northern tip of the Western Veil and northern tip of the Eastern Veil is an uncatalogued section known as Pickering’s Triangle.  This slender triangular section of the remnant is brighter than either NGC 6974 or 6879. It narrows from north to south extending into a region called The Funnel.

I have view both the Western and Eastern Veil in a four-inch apochromatic refractor in really dark skies.  Some people find the Veil easier to see with nebula filters, such as an O-III filter. These filters only pass a narrow band of wavelengths, thus not all of the light emitted from the nebula reaches the eye.  For some, the contrast improvement overcomes the diminished light throughput.  For me, I have found observing the Veil with filters from a really dark site does not improve my ability to see the nebula.  I prefer the unfiltered view.

Earlier this month, I had the opportunity to view the Western Veil through a 24-inch  Newtonian.  The telescope had its newly recoated mirror installed that day. The Veil was the first light with the new coating.  The sky transparency was poor due to haze from numerous fires in western States 1500 miles away. So we used an O-III filter to improve the contrast.  The filter also diminished the glow of 52 Cygni.  Only about one-third of the Network Nebula was in the eyepiece, but it was the brightest I have ever seen this section of the Veil.

My image of the Veil was taken with an Askar FRA400 refractor.  This is a 72mm f/5.6 quintuplet Petzval Flat-Field Apo.  I used a 0.7x focal reducer with a SBIG STF-8300C CCD camera on a Celestron CGEM II mount.  The exposure was 220 minutes.  This picture nicely frames the entire Veil Nebula complex.

To enlarge Jim’s wide-field image, with identifications as following, click on the black dot.

Glenn Chaple: Observer from Massachusetts

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 H14 and H15 – 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. 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. 

(L) Veil Nebula East, as with a 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)

Roger Ivester: Observer from North Carolina

Veil Nebula

Date:  September 6, 2020

10-inch f/4.5 Newtonian

Sketch Eyepiece: 26mm 70º AF

Filter: Oxygen III 

Magnification: 44x

Sketch Field: 1.6º

NELM: 5.1 

I have observed the Veil Nebula many times over the years, but never making a sketch due to the complexity.  However, this was going to be my year for a sketch.  First, I aimed my telescope at NGC 6960, known to most amateurs as the Western Veil Nebula.  

Starting with a magnification of 44x and an oxygen III filter, the nebula appeared fairly bright, oriented N-S.  Bright star 52 Cygni is situated almost in the center, but just off the western edge.  The southern section, just south of 52 Cygni is mostly diffuse and fans out into a broad faint tail. The northern part of this nebula extends to a point.     

NGC 6992/6995, know as the Eastern Veil Nebula makes an arc, and extends for well over a degree.  The most prominent part, which draws my eye immediately, has always been the forked tail at the southern tip.  (See the following sketch) 

Anas Sawallha:  Observer from Jordan

This months target proved difficult, due to my telescope having only 5-inches of aperture.  The most difficult, was the Western Veil, which required averted vision.  I made my sketch completely with averted vision.  However, the thing that helped me is the dark location which I observe from.

The Eastern Veil was much easier to sketch, and without the use of a filter.  

Western Veil sketch below, and Eastern Veil following:

Michael Brown: Observer from Massachusetts

I observed the Veil Nebula with my 8-inch SCT and 9mm eyepiece, on August 22, September 11, and September 18, 2020.  I have always found the Veil to be a unique object because of its faintness, its overall large size so that only a portion can be viewed in one eyepiece field, and the slenderness of the main sections.

I find the eastern section (NGC 6992) to be the brightest part of the nebula and is clearly visible even without a filter.  By moving the drive motor slowly in the right direction, I can follow the arc of this loop section over multiple field diameters, running from northwest to southeast and then southwest.  The narrow, northwest section appears to be most distinct visually.

The western section (NGC 6960) has a bright star, 52 Cygni, in the foreground, making it easy to know the telescope is pointed correctly.  The star appears yellow and is binary, with a dim, closely-spaced companion to the northeast.  The nebulosity of this portion of the Veil is narrower and dimmer than the eastern section but still fairly easily visible.  The portion north of 52 Cygni is somewhat easier to spot than the portion south of the star.  

Using my UHC filter makes the Veil Nebula even more obvious by increasing contrast between nebula and background sky.  The east section seems to have a texture as viewed through the filter.  I also could see hints of nebulosity between the two arcs; perhaps I was seeing “Pickering’s Triangle” but I am not certain.

I took photographs of the Veil Nebula on September 20, 2020.  Rather than take guided photos through the telescope, my original idea was to “piggyback” my digital SLR camera on the telescope with a 300 mm telephoto lens and try to capture the entire nebula.  However, I found it difficult to frame the photo such that I was confident that the entire nebula was being captured, so I decided to photograph the east and west sections separately.  I guessed that 30-second exposures would not result in much drift, even without guiding, if the scope was reasonably well-aligned and the drive was running.  I was mistaken, and there was considerable movement even in 30 seconds, so that the stars are far from points.  Despite this flaw, the nebula is visible in the photos with fine tendrils and other details apparent.  Each photo is a stack of 60 exposures for a total exposure of 30 minutes.  

The photos seem to confirm my visual impression that the brightest portions include the eastern loop and the northern portion of the west loop. This was my first attempt at deep-sky photography using the telephoto lens (I previously used it for the 2017 solar eclipse and Comet Neowise).  While I think I will mostly continue to take astrophotos through the scope, I can see a place for the telephoto for wider shots, but in the future I will take guided photos (or much shorter individual exposures).

Venu Venugopal: Observer from Massachusetts

Formed about 8000 years ago, Veil Nebula and related parts of the nebula have different nicknames, some of the most famous of which include these: Cygnus Loop, Cirrus Nebula, Filamentary Nebula, Witch’s Broom Nebula, Bridal Veil Nebula, Finger of God, Network Nebula etc. At the center of the Veil Nebula has a black hole created when the internal collapse of the massive star sent shock waves emanating out in all directions. 

The following image was taken of the Eastern Veil with 72 ED refractor and an H-Alpha, H-Beta, OIII filter  (Triad) – 20 minute total exposure.  The image is a composite of two images stitched side by side and requires further processing for the uniformity of the color balance.

The Western nebula was taken with an 8-inch Newtonian Reflector, again with the same filter / exposure combination as above.

This last image is just a try to get a mosaic, made from 7 images of the Cygnus loop which I could not complete due to the skies getting cloudy by the time I imaged part of the loop, taken with the 72ED.  I included the following image as just a learning exercise.

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