Arp188
Arp188 | Tadpole Galaxy - Click here for full resolution
The Tadpole Galaxy, also known as UGC 10214 and Arp 188, is a disrupted barred spiral galaxy located 420 million light-years from Earth in the northern constellation Draco. Its most dramatic feature is a trail of stars about 280,000 light-years long. Its size has been attributed to a merger with a smaller galaxy that is believed to have occurred about 100 million years ago. The galaxy is filled with bright blue star clusters triggered by the merger, some containing as many as one million stars. It is the largest disrupted spiral galaxy of its sort.
source: wikipedia
NGC/IC:
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Object:
Constellation:
R.A.:
Dec:
Transit date:
Transit Alt:
UGC 10214
Tadpole Galaxy
Galaxy
Draco
16h 06m 03s
+55° 25.0′
25 June
72º N
Conditions
Arp188 is best visible in summer time. Peak altitude in June is 72°. Images were taken over thirteen nights from early until late June 2024 from the remote observatory at IC Astronomy in Oria, Spain. No images were taken around the full moon period, roughly the third week of June.
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
The Arp catalogue is a very interesting catalogue with deep sky objects of unique morphology. But many of them are quite small. Arp188, although certainly not the smallest in the catalogue is such a small object with a total length of not more than 3.6 arcmin. So the long focal length setup with the CDK14 is a good way of imaging them. But the full-frame camera is too much. Therefore the image here is cropped in a bit to highlight Arp188 better. Arp188 was captured using both Luminance (180s) as well as Red, Green and Blue (300s) broadband filters. A total of 20h of data was acquired.
Resolution (original)
Focal length
Pixel size
Resolution
Field of View (original)
Image center
3300 × 2200 px (7.3 MP)
2585 mm @ f/7.3
3.8 µm
0.30 arcsec/px
16' x 11'
RA: 16h 06m 08.451s
Dec: +55° 25’ 31.03”
Processing
All images were calibrated using Darks (50), and Flats (25), registered and integrated using the FastBatchPreProcessing (WBPP) script in PixInsight. The processing followed a fairly standard pattern.
Any gradients were removed from the Red, Green and Blue channels before they were combined, colour calibrated (SPCC), and deconvolved (BXT). Stars were removed and kept for later processing. The RGB image was stretched using several iterations of GHS, followed by some contrast and saturation enhancements using CurvesTransformation. Noise was removed with NoiseXTerminator.
Any gradient in Luminance was removed using the new automatic DBE script from SetiAstro. Deconvolution (BXT) was followed by StarXTerminator to create a starless image. The luminance stars would not be further used. The starless luminance was stretched using several iterations of GHS and HT. The image was further enhanced by reducing the noise (NoiseXTerminator) and increasing the sharpness (UnsharpMask). Brightness and contrast were enhanced using CurvesTransformation and HistogramTransformation. Four dust bunnies were left in the luminance image, probably indicating the need of a new set of flats. Although they were not very well visible, they were completely removed using the CloneStamp tool. I tried the Blemish Blaster script from SetiAstro during the linear stage, but found that I could not set the STF stretch such that the dust spots could be reliably identified.
The RGB stars were stretched using the automated StarStretch script from SetiAstro.
The luminance was now added to the RGB image, and the stars were put back in using the screening function in PixelMath. The background level was adjusted to 0.07 using BackgroundNeutralization, to align it with my other images. A final crop was applied to let the galaxy come out a bit better from this way too big full frame image.
Processing workflow (click to enlarge)
This image has been published on Astrobin and received Top Pick nomination status.
