Arp84
Arp84 | NGC5395, NGC5394 - Click here for full resolution
NGC 5395 is an interacting spiral galaxy located at a distance of 160 million light years, in the constellation Canes Venatici. It was discovered by William Herschel on May 16, 1787. NGC 5395 and NGC 5394 are included in the Atlas of Peculiar Galaxies as Arp 84 in the category "Spiral galaxies with large high surface brightness companions". NGC 5395 is the larger spiral galaxy interacting with smaller barred spiral galaxy, NGC 5394. NGC 5395 is nearly face-on, with a diameter of around 140,000 light-years across. NGC 5395 has a bright central region and is distorted due to the interaction with NGC 5394. The larger of the two rings around the galaxy forms a ring off the center of the galaxy. Dust lanes can be seen throughout the galaxy. NGC 5394 is the smaller barred spiral galaxy. It has an oval disk, with a diameter of around 90 thousand light years across.
source: wikipedia
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NGC5395, NGC5394
Arp84
Galaxy
Canes Venatici
13h 58m 38.0s
+37° 25′ 28″
09 May
90º S
Conditions
Arp84 is visible in spring time, during galaxy season. Peak altitude in early May is 90°. Such straight up position can be challenging for telescope/mount, so that is something to be aware of. Images were taken over six nights from late May until early June 2023 from the remote observatory at IC Astronomy in Oria, Spain.
Equipment
The default rig at the observatory was used. This is built around 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 1.8.9-2
Imaging
This was my first image from the Atlas of Peculiar Galaxies, better known as the Arp catalogue. Technically it is the second, as the quite normal-shaped Pinwheel galaxy (M101) is also found in the Arp catalogue (Arp26). Objects in the Arp catalogue have most interesting morphology, but they are all small and many of them not very bright. So a long focal length setup is a good way of imaging them. Imaging itself was pretty straight-forward, with sufficient altitude of the object. Arp84 was captured using both Luminance (180s) as well as Red, Green and Blue (300s) broadband filters. A total of just over 22h of data was acquired.
Resolution (original)
Focal length
Pixel size
Resolution
Field of View (original)
Image center
4000 × 3000 px (12.0 MP)
2585 mm @ f/7.3
3.8 µm
0.30 arcsec/px
20' x 15'
RA: 13h 58m 36.866s
Dec: +37° 26’ 19.12”
Processing
All images were calibrated using Darks (50), and Flats (25), registered and integrated using the WeightedBatchPreProcessing (WBPP) script in PixInsight. The processing followed a fairly standard pattern.
Red, Green and Blue channels were combined, some stacking artefacts at the edges were removed (DynamicCrop), gradient removed (GraXpert), calibrated (SPCC), and deconvolved (BXT). Before stretching (GHS), the stars were removed to create the stars image that would later be added back. Saturation and contrast were enhanced (CurvesTransformation) and noise was removed (NoiseXTerminator). The luminance channel followed the same pattern excluding the colour calibration.
Luminance was combined with the RGB image using LRGBCombination. Brightness was a bit too much, so the lightness slider was adjusted to 0.55 (instead of 0.5). These sliders are a kind of midpoint adjustment, so a larger Lightness number gives a darker result. Luminance stars were discarded, only RGB stars were used. They were stretched using StarStretch at strength 6 and colour boost 1. ImageBlend was used again to put the stars back in, in screen mode.
The object is a bit weirdly shaped and I was not completely sure what position would look best, so when doing the final crop (original image had way too much field of view), I rotated around quite a bit. I ultimately settled on a composition where North is to the right. A final step of contrast enhanced was achieved with a mild LocalHistogramEqualization (radius 30, contrast 1.5, amount 0.4). The Final step in processing was the adjustment of the background level to 0.07 to align with other images.
Processing workflow (click to enlarge)
This image has been published on Astrobin and received Top Pick Status.
