NGC5905, NGC5908
NGC5905 and NGC5908 Galaxies (slight crop) - Click here for full resolution
NGC5905 and NGC5908 are two galaxies, around 172 million lightyears away from earth, in the constellation Draco. Both galaxies were discovered by William Herschell on 05 May 1788. NGC5905 is a beautiful spiral galaxy (SAb), that is visible face-on. It contrasts nicely with NGC5908, which is a barred spiral galaxy (SBb) and visible in an edge-on view. The distance between the two galaxies is approximately 500k lightyears.
source: various internet searches
NGC/IC:
Other Names:
Object:
Constellation:
R.A.:
Dec:
Transit date:
Transit Alt:
NGC5905, NGC5908
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Galaxy
Draco
15h 15m 23s
+55° 31′ 02”
28 May
72º N
Conditions
NGC5905 and NGC5908 are technically visible all year around, but best time for observing is spring/summer time. At the time of imaging it reached peak altitudes to just over 70° at my location. Images were taken from the remote hosting site IC Astronomy in Spain across five different nights in May 2024.
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” RGB 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
Imaging was pretty straight-forward, with sufficient altitude of the object. NGC5905 and NGC5908 were captured using R,G and B broadband filters and no Luminance. A total of almost 22h of data was acquired.
Resolution (original)
Focal length
Pixel size
Resolution
Field of View (original)
Image center
9392 × 6112 px (57.4 MP)
2585 mm @ f/7.2
3.8 µm
0.30 arcsec/px
47' x 31’
RA: 15h 15m 52.247s
Dec: +55° 29’ 01.48”
Processing
All images were calibrated using Darks (50), Flats (25) and Flat-Darks (25), registered and integrated using the WeightedBatchPreProcessing (WBPP) script in PixInsight. Processing followed a pretty standard pattern. After removing small stacking artefacts, gradients were removed in the individual channels using GraXpert and an RGB image was composed. This was colour calibrated using SPCC and deconvolved with BXT. I have come to appreciate to stretch the stars separately from the main object, whether this is a nebula or a galaxy. Optimal stretching of the main object, very often leads to some unwanted effects on star morphology, colour or brightness. So stars were removed with SXT and then the galaxies were stretched with StatisticalStretch, a relatively new script from SetiAstro. This gave a very good result. The only further processing involved some brightness and saturation enhancements with CurvesTransformation. For the stars, a SetiAstro script was used as well, called StarStretch. I find that using stretch factor 6, instead of the default 5, gives me a bit better results.
Stars were then combined with the RGB image using PixelMath. There was not a whole lot of noise present, but a mild (0.7) noise reduction with NXT definitely cleaned up the image a bit. Some final touches included a bit more contrast and setting the background value to a standardized 0.07.
Processing workflow (click to enlarge)
This image has been published on Astrobin.
