There are several constellations considered autumn objects, and Cygnus is definitely one of them. And there are several popular astroimaging targets in the Cygnus, and Cygnus Loop (Veil) nebula is undoubtedly one of them! I have already imaged this target a few times, but it was either a wide-field image done with a telephoto lens, or a nebula part made with a longer focal-length instrument.
This time I have used my 2022 purchase TecnoSky 90-540 Owl refractor with 0.8x focal reducer and QHY268M camera, which has an APS-C format chip. This combination allowed me to achieve a decent detail level with only a two-panels mosaic.
Cygnus Loop nebula is a cloud of ionized gas, a large supernova remnant measuring nearly three degrees across. Some parts of this object emit in the visible part of the electromagnetic range, but others are only visible in infrared, X-ray, or radio images. Although the Cygnus Loop complex originates in a single event – a supernova explosion, it contains several catalog entities. NGC6960 is the so-called Western Veil, also known as Witch’s Broom. Easter Veil is made up of three items: NGC6992, NGC6995, and IC1340. Between these two parts, there is a segment of relatively faint nebulosity discovered photographically in 1904 – the Pickering’s Triangle. NGC6974 and NGC6979 are two more objects identified today with two bright knots of nebulosity in the northern edge of the loop. NGC6979 was reported by William Herschel. It is sometimes taken to refer to Pickering’s Triangle, but the Triangle is probably not what Herschel saw.
The source supernova was a star about 20 times more massive than Sun. It exploded between 10,000 and 20,000 years ago, and at that time it was visible in the daytime – brighter than Venus. Recent distance estimations locate the Cygnus Loop about 2,400 light-years away from us. It is expanding at a velocity of about 1.5 million kilometers per hour.
The nebula was discovered in 1784 by William Herschel. It has relatively low surface brightness, but still can be observed visually. 8 inches aperture telescope with an O-III filter shows the delicate lacework. A larger telescope will show more and more, and in a 14-16 inches telescope, Cygnus Loop is a spectacular view.
The image above is a two-panel mosaic made through narrowband filters. Each panel is 6 hours of total exposure time, equally split for Ha, OIII, and SII filters. Many delicate features and details were recorded in the image of this quite large area in the sky. Six apparent Moon diameters can fit this image in width, so as you see, the Cygnus Loop is quite large. It is not the dimensions that prevent seeing it with the naked eye, but faintness.
Below there is Cygnus Loop with stars removed, and negative, monochromatic data captured with hydrogen alpha filter only.
Image technical data: Date: July-October 2022 Location: Nieborowice, Poland Telescope: Tecnosky 90/540 Owl triplet Corrector: TS FF/FR 0.8x Camera: QHY268M Mount: EQ6 Guiding: ASI290MM + Evoguide ED50 Exposure: two panels, 3x2 hours each through Ha, Oiii, and Sii filters Conditions: Bortle 6, transparency medium-good, seeing medium
