Object

M 57 The Ring Nebula (NGC 6720) and IC 1296

Object Information

Image information

Object Type

Planetary Nebula

Instrument

LX200GPS 14” OTA @ F5.3 effective FL≈1868 mm

Constellation

Lyra

Guiding

SXV / SkyWatcher 80mm achro @ F/6

Magnitude

+8.8

Focal Reducer

Optec NextGen 0.5x

Coordinates

RA 18:53.6 Dec +33:02

Mount

Paramount ME

Size

1.4 x 1.0 arc min

Location

Stoney Hills, S.E England

Distance

2000 ~ 2300 Light Years

Acquisition Date

05 - 12th August 2007

Notes

The Ring Nebula M57 is a show piece planetary nebula. It is visible as a very obvious distinct ring even with small telescopes. It is also easily found lying between Sheliak and Sulafat (Beta & Gamma Lyrae), the two most southerly stars in the constellation of Lyra.

Certain stars at the end of their life become unstable, the image above shows the central star which has explosively ejected a shell of gas. The gases seem mostly to be Hydrogen, Helium, Oxygen and Nitrogen. The gasses are ionised and and emit light in characteristic colours.

The extremely faint outer halo glows in the red of hydrogen. Further out another shell of gas is just visible. The central bright ring is around 0.9 light years in diameter and the outer halo about 2.4 light years. It is expanding at 20 to 30 kilometres per second or 1 arcsec per century as seen from earth.

M57 was exquisitely imaged by the 8.2 meter Subaru Telescope in 1999. Links to the image and the ‘scope are below.

http://www.naoj.org/Pressrelease/1999/09/M57_ha_300.jpg

http://www.naoj.org/Introduction/telescope.html

Also clearly visible in the image is the galaxy IC 1296 lying some 200,000,000 light years distant.

M 57 was discovered by Antoine Darquier de Pellepoix (Darquier) in January 1779 and catalogued by Charles Messier. Halos discovered by J C Duncan in 1935.

Capture Device

Starlight-Xpress SXV-H9 Sony ICX285AL Exview HAD Cooled CCD Array 1392 x 1040 @ 6.45uM / Pixel 

Filter Type

Astronomik Type IIc RGB + Ha(12nm)

Colour Technique

L+HaRGB

FOV

≈16.47 x 12.31 arc mins (0.71 arcsec/pixel) before cropping

Exposure

970.57 min (16.18 hours) Total

Integration

L (33 x 300 sec bin 1x1)

R (22 x 215 sec bin 2x2)

G (22 x 167 sec bin 2x2)

B (21 x 230 sec bin 2x2)

Ha (20 x 900 sec bin 1x1)

Ha (19 x 900 sec bin 2x2)

Notes

Inspired by the images from professionals such as those produced by the Subaru Telescope and from experts such as Rob Gendler I set out to image the central ring of this object at high resolution and also include some of the extended and extremely faint halo surrounding it.

Around 23 hours of data was captured in the imaging runs but sub exposures with FWHM exceeding around 1.8 arcsec (measured by CCDInspector) were rejected giving 16 hours of data. Bias and Flat calibrations applied and Darks applied to the 900 sec Hydrogen Alpha subs. Sigma combined in Maxim. Clear and Ha(1x1) data combined and used as LRGB luminance in PSCS2. Ha(2x2) rescaled and merged using layers. Levels and sharpening selectively applied. Emphasis being placed on resolving structure in the ring. Binning the Ha at 2x2 was used to gain sensitively at the expense of resolution for the very faint outer halo.