M76
M76, Little Dumbbell - Click here for full resolution
Messier 76 or the Little Dumbbell Nebula, is a planetary nebula in the northern constellation of Perseus. It was discovered by Pierre Méchain in 1780. It was first classified as a planetary nebula in 1918 by the astronomer Heber Doust Curtis. M76 is currently classed as a type of bipolar planetary nebula (BPN), composed of a ring which we see edge-on as the central bar structure, and two lobes on either opening of the ring. The progenitor star ejected the ring when it was in the asymptotic giant branch, before it had become a planetary nebula. Soon afterward the star expelled the rest of its outer layers, creating the two lobes, and leaving a white dwarf as the remnant of the star's core. Distance to M76 is estimated to be 2,500 light years.
source: Wikipedia
NGC/IC:
Other Names:
Object:
Constellation:
R.A.:
Dec:
Transit date:
Transit Alt:
NGC650/651
Little Dumbbell, Barbell Nebula, Cork Nebula
Planetary Nebula
Perseus
01h 42m 18s
-51° 34.2′
17 November
76º N
Conditions
M76 can be very well observed in Autumn time, with maximum altitudes reaching 76°. Here, M76 was photographed over 12 nights during the month of August 2024 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, and 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 1.8.9-3
Imaging
There is multiple ways in which M76 can be photographed. A straightforward RGB image works very well. Here, an HOO image was created to give it that typical blue/orange look. It is a very small target, so the long focal length of the CDK14 works very well. The FoV of the full-frame camera is far too big, so the final image was cropped in heavily to an 10x12 arcminute field of view.
Resolution (original)
Focal length
Pixel size
Resolution
Field of View (original)
Image center
2500 × 2000 px (5 MP)
2585 mm @ f/7.3
3.8 µm
0.30 arcsec/px
12' x 10'
RA: 01h 42m 19.243s
Dec: +51° 34’ 25.81”
Processing
The processing was kept very similar to the processing of M16. All images were calibrated using Darks (50), Flats (50) and Flat-Darks, registered and integrated using the WeightedBatchPreProcessing (WBPP) script in PixInsight.
After stacking artefacts were removed using DynamicCrop, individual colour channels were processed by gradient removal (GraXpert) and deconvolution (BXT).
The individual Ha and OIII channels were carefully stretched using GHS so that maximum detail in the nebula was retained without over-stretching any of the bright central parts of both channels. Also they were stretched so that they were somewhat similar in signal strength. The HOO image was created using ChannelCombination. Base colour was achieved using NarrowbandNormalization in HOO mode, Ha Lightness and a slight reduction of the OIII channel to about 0.9. From there blues were a bit intensified using CurvesTransformation. Noise was removed using NXT before enhancing sharpness with LocalHistogramEqualization and UnsharpMask. Contrast in the lower range of the image was enhanced using CurvesTransformation.
The R, G and B channels were combined using ChannelCombination as well, then calibrated using SPCC. The stars were extracted (SXT) and stretched using the SetiAstro StarStretch script. It turned out that SXT had left a little bit of the nebula behind. First it was tried to take this out using the Blemish Blaster from SetiAstro. But that tool still left a bit of the artefact behind. Therefore the true and trusted CloneStamp tool was used to effectively remove the artefact.
The stars were combined with the HOO image using PixelMath and then the image was cropped significantly to make the nebula stand out.
Processing workflow (click to enlarge)
This image has been published on Astrobin and received Top Pick nomination status.
