M77 | Arp37
Messier 77 | Arp37 - Click here for full resolution
Messier 77, also known as Arp37, NGC 1068 or the Squid Galaxy, is a barred spiral galaxy in the constellation Cetus. It is about 47 million light-years away from Earth, and was discovered by Pierre Méchain in 1780, who originally described it as a nebula. Méchain then communicated his discovery to Charles Messier, who subsequently listed the object in his catalog. Both Messier and William Herschel described this galaxy as a star cluster. Today, however, the object is known to be a galaxy. It is one of the brightest Seyfert galaxies visible from Earth. The morphological classification of NGC 1068 in the De Vaucouleurs system is (R)SA(rs)b, where the '(R)' indicates an outer ring-like structure, 'SA' denotes a non-barred spiral, '(rs)' means a transitional inner ring/spiral structure, and 'b' says the spiral arms are moderately wound. Only one supernova has been detected in Messier 77. The supernova, named SN 2018ivc, was discovered on 24 November 2018 by the DLT40 Survey. It is a type II supernova, and at discovery it was 15th magnitude and brightening. In February 2022 the European Southern Observatory found a cloud of cosmic dust at the centre of Messier 77 hiding a supermassive black hole.
source: wikipedia
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NGC1068
Arp37, Squid Galaxy
Galaxy
Cetus
02h 42m 41s
-00° 00.8′
03 December
52º S
Conditions
M77 is best visible in the Autumn time, when peak altitudes reach 52° in the South. The current image was taken a bit early in its cycle. Images were shot over eleven nights throughout the months of August and September 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” LRGB 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
M77 is a typical broadband object, best recorded using an LRGB imaging scheme. The challenge is to extract as much from the gas rings surrounding the core of the galaxy as possible. This is mainly achieved by shooting lots of luminance images. For this image a total of 196 luminance images were shot, totalling almost 10h of exposure. Colour was obtained by shooting R, G and B frames, making up for another 10h of exposure. This makes the total almost 20h of exposure. The field of view of the rig used was a bit too large for this relatively small target, so the final image has been cropped to focus on the galaxy itself.
Resolution (original)
Focal length
Pixel size
Resolution
Field of View (original)
Image center
6000 × 4000 px (24 MP)
2585 mm @ f/7.3
3.8 µm
0.30 arcsec/px
47' x 31'
RA: 02h 42m 40.122s
Dec: -00° 01’ 05.15”
Processing
All images were calibrated using Darks (50), Flats (50) and FlatDarks (50), registered and integrated using the WeightedBatchPreProcessing (WBPP) script in PixInsight. The start of the processing was the same for all stacked images. After cropping away the stacking artefacts, gradients were removed with GraXpert and deconvolution was applied using BlurXTerminator (BXT).
The luminance image now had the stars removed using StarXTerminator (SXT) and carefully stretched using multiple runs of GHS. As much as this was done carefully, it was also done somewhat aggressively to get out as much of the faint nebulous rings as possible, without over-stretching the core of the galaxy. Overstretching the core would also wash out colour later in the process when RGB data would be added. Contrast in the stretched image was further enhanced using CurvesTransformation and LocalHistogramEqualization with a small kernel radius (64). The image did not look particularly noisy, but some noise removal using NoiseXTerminator definitely helped making it look very smooth. A final touch of sharpness was added using UnSharpmask.
The R, G and B channels were combined using ChannelCombination and colour calibrated using SPCC. Then the stars were taken out with SXT. The starless image was stretched using GHS in the colour mode, to create a rather saturated image with vivid colours. CurvesTransformation was used to add some extra contrast and warmth, using the c-channel. Noise was removed using NXT, followed by a further smoothing of the image using Convolution. The starless luminance image was now added using LRGBCombination. This is always a very satisfying moment in the processing. Two moderately interesting images together transform into a new nice and crisp image.
The RGB stars were stretched using the automated Star Stretch script from SetiAstro and colour was further boosted with CurvesTransformation. The image was smoothened with Convolution before the Luminance stars were added. The Luminance stars were also stretched using the Star Stretch script. It is not a very dense star field and the default stretch factor of 5 made the image look a bit dull. So a stretch factor of 6.2 was applied to both the RGB and Lum stars. This made the star field much richer and interesting. It enhanced the overall impression of the final image. Some of the diffraction spikes on the brighter stars came through nicely. And the large star in front of the galaxy is nicely popping out.
The stars were added to the starless LRGB image using the CombineImages tool. The background was adjusted to 0.07 to be in line with all my other images. As mentioned above, the field of view of the OTA and camera combination is quite large for this rather small target. So the final image is approximately a 65% crop of the original image.
Processing workflow (click to enlarge)
This image has been published on Astrobin.
