Sh2-290
Sh2-290 - Click here for full resolution
Sh2-290 ( also known as Abell 31) is an ancient planetary nebula in the constellation of Cancer. It is estimated to be about 2,000 light years away. Although it is one of the largest planetary nebulae in the sky, it is not very bright. The central star of the planetary nebula is a white dwarf with a spectral type of DAO. The white dwarf is the dead remains of a star that existed but had died leaving behind Sh2-290 and the white dwarf. Sh2-290 is made mostly of hydrogen and oxygen gas. The nebula has a blue central region being most of the nebula and a red ring around this blue region. The nebula due to its ancient age has its gas being dispersed into the interstellar medium. Some nearby objects include the Beehive Cluster (a cluster of about 1000 stars), IC 523 (a galaxy), NGC 2731 (a spiral galaxy) and M 67 (an old cluster of stars sometimes known as the King cobra cluster).
source: Wikipedia
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Abell 31
Planetary Nebula
Cancer
08h 54m 13s
+08° 53.8′
2 kly
15.5
20 February
61º S
Conditions
Sh2-290 is a great winter target. A maximum altitude of 61° is reached in mid February. For some reason I had started imaging this target back in May 2024, which was a bit odd. I must have been keen to find a faint narrowband target at the time. Anyway, most of the imaging was done in late November and throughout December 2024. Sh2-290 was photographed over 11 nights during that time from the remote observatory at IC Astronomy in Oria, Spain.
Equipment
The default rig at the observatory was used. The core of this rig is a Planewave CDK-14 telescope on a 10Micron GM2000 mount, coupled to a Moravian C3-61000 Pro full-frame camera. The RoboTarget module in Voyager Advanced automated the process to find optimal time-slots during astronomical night.
Telescope
Mount
Camera
Filters
Guiding
Accessoires
Software
Planewave CDK14, Optec Gemini Rotating focuser
10Micron GM2000HPS, custom pier
Moravian C3-61000 Pro, cooled to -10 ºC
Chroma 2” H-alpha, OIII (both 3nm) and Red, Green and Blue unmounted, Moravian filterwheel L, 7-position
Unguided
Compulab Tensor I-22, Windows 11, Dragonfly, Pegasus Ultimate Powerbox v2
Voyager Advanced, Viking, Mountwizzard4, Astroplanner, PixInsight 1.9.2
Imaging
Sh2-290 as a planetary nebula is a typical narrowband object, with main visibility in Ha and OIII. There is not much SII signal present, if any at all. So the image was shot as a typical dual-band image, using 10 min. exposures for each of the narrowband filters. For star colours, RGB images were collected as 10x3 minute subs. The total exposure was 20h.
Resolution (original)
Focal length
Pixel size
Resolution
Field of View (original)
Rotation
Image center
9373 × 6213 px (58.2 MP)
2585 mm @ f/7.3
3.8 µm
0.30 arcsec/px
47' x 31'
0.1°
RA: 08h 54m 13.200s
Dec: +08° 53’ 38.13”
Processing
All images were calibrated using Darks (50), Flats (50) and Flat-Darks (50), registered and integrated using the WeightedBatchPreProcessing (WBPP) in PixInsight. All further processing was done in PixInsight, including the use of scripts and tools developed by RC-Astro, SetiAstro, GraXpert, and others. For a step-by-step description of the processing techniques applied, see process flow below.
The target was probably not present in the MARS database, as MultiscaleGradientCorrection (MGC) could not be completed. So gradient removal was done using GraXpert. The images were generally quite faint, and it was difficult to get the right amount of contrast in them.
At first NBColourmapper was tried to get to the desired image, but in the end I found that for this image the regular NarrowbandNormalization gave a better result, so I used that.
The rest of the processing followed a very standard processing workflow.
Processing workflow (click to enlarge)
This image has been published on Astrobin
