M57 (remastered)

Another version of M57 nebula based on the material gathered during the night 28th-29th of Jun.
The nebula itself is better seen (then in the previous version) with its central white dwarf.

Night 28th-29th of Jun 2017; Kyiv
Field of view: 15x15 arcminutes; North is up

Setup: SkyWatcher 15075 OTAW / EQ5 motorized(no guiding) + Canon EOS600D
97*30s; ISO=800

M57

M57 "Ring" Nebula
Gaseous shell (~1 l.y. in diameter) surrounds dead star: a white dwarf (faint star in the center of the nebula). The white dwarf -- a remnant of the star, in fact, dead star's nucleus -- is hot enough to emit powerful ultraviolet radiation. That ultraviolet emission makes surrounding gases to glow.

Night 28th-29th of Jun 2017
Kyiv

North is up.

Setup: SkyWatcher 15075 OTAW / EQ5 motorized(no guiding) + Canon EOS600D
97*30s; ISO=800

Size of the field is 39.4 x 39.4 arcmin (by nova.astrometry.net). A faint galaxy is visile near the nebula:

M57 Remastered

This is an image of Messier 57 nebula obtained using frames captured in the night from 16 to 17 of June 2016 with Canon EOS 600D + Canon EF-S F/4-5.6 55-250mm IS II lens (@ 250mm; F/7) fixed at EQ5 motorized mount.

The nebula is a remnant of a star, which ended active life and expelled its outer layers. A core of the dead star -- a white dwarf -- could be hardly distinguished in the center of the nebula.

Greenish color of the nebula is caused by double-ionized oxygen; a reddish color of outer layers corresponds to hydrogen and ionized nitrogen. A density of glowing gas is very small yet many times denser than interstellar medium.

Estimated size of the nebula is about a light-year, a distance to it is ~2300 light-years.

The previous image was made using DeepSkyStacker: good yet not perfect program. This picture (which is definitely more realistic) is a result of stacking of 40 frames (30s exposure each) using FITStacker program. Images were calibrated and aligned using IRIS (15 offsets, 15 darks, and 15 flats were used for calibration).

Ring Nebula M57

Night from 16 to 17 of June was almost clear. Humidity was extremely high, lens became steamed up quickly so I used a hairdryer to warm it up.  Near midnight stars had been dimmed by a haze.

This was the second test of my new EQ-5 mount with motor drives. It was used as a sky-tracker which holds Canon EOS 600D DSLR.

I chose M57 nebula for test capture. I made 40 light frames in total with exposure of 30 sec each (qDSLRdashboard Android application was used to control the camera). Canon EF-S F/4-5.6 55-250mm IS II lens was used at 250mm focal length and F/7 stop (to reduce optical aberrations).
Frames were averaged with DeepSkyStacker (using 15 dark frames, 15 offset frames, and 16 flats). Darks and offsets were captured right after the main session, flats were captured next morning.

The result (1x1 arcdegree crop) is shown below, 4x zoomed part is in the inset.

Ring Nebula (Messier 57) is a planetary nebula: a gas shell ejected by a star at the end of its active life. A size of the nebula is about a light year, an estimated distance to it is ~2300 light years. The nebula glows because a star's remnant (white dwarf) in the center of it ionizes atoms which compose the expanding shell. A blue-green color of inner parts of the nebula caused by an emission of double-ionized oxygen, reddish color of outer layers caused by hydrogen and ionized nitrogen emission lines.