M102
M102 - Click here for full resolution
Messier 102 is a galaxy listed in the Messier Catalogue that cannot be unambiguously identified. Its original discoverer Pierre Méchain retracted his discovery two years after publication and said that it was a duplicate observation of Messier 101. Later historical evidence favors that M102 is actually the galaxy NGC 5866, although other galaxies have been suggested as possible identities. The National Aeronautics and Space Administration (NASA) considers it to be the same as NGC 5866. NGC 5866 (also called the Spindle Galaxy) is a lenticular galaxy in the constellation Draco.
source: wikipedia
NGC/IC:
Other Names:
Object:
Constellation:
R.A.:
Dec:
Transit date:
Transit Alt:
NGC5866
Spindle Galaxy
Galaxy
Draco
15h 06m 30s
+55° 45.7’
26 May
72º N
Conditions
M102 is visible in spring time, during galaxy season. Peak altitude in late May is 72°. Images were taken throughout the month of June 2024 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
M102 is a relatively small object, with not a lot of structure. Most of the structure is found as a lane of dust through the center. It is located near some very bright stars, of which HD134023 is the closest. So in the final crop, this star was considered to be part of the composition. M102 was captured using both Luminance (180s) as well as Red, Green and Blue (300s) broadband filters. During capturing some rejected Red frames were not correctly deleted from Voyager Robotarget, so it assumed all Red images had been taken while in reality the plan was to shoot 10 more. Nevertheless a total of just under 22h of data was acquired.
Resolution (original)
Focal length
Pixel size
Resolution
Field of View (original)
Image center
4713 × 3117 px (14.7 MP)
2585 mm @ f/7.3
3.8 µm
0.30 arcsec/px
23' x 15'
RA: 15h 06m 10.562s
Dec: +55° 44’ 08.40”
Processing
All images were calibrated using Darks (50), Flats (25) and Flat-Darks (50), registered and integrated using the FastBatchPreProcessing (WBPP) script in PixInsight. This is a new script and can be used as a replacement for the WeightedBatchPreProcessing. As the name implies, the script is fully geared towards fast calibration and stacking of image. It does this at the cost of customisation possibilities. With this first dataset, I did not miss at all any option to fine-tune the progress. However, the incremental speed (about a factor of 10!) is highly welcomed.
Red, Green and Blue channels had their gradient removed (GraXpert), combined, calibrated (SPCC), and deconvolved (BXT). Before stretching (GHS+HT), the stars were removed to create the stars image that would later be added back. Saturation and contrast were enhanced (CurvesTransformation) and some mild colour noise was removed by applying a small blue using convolution. Detail would come back from the luminance later. That luminance channel followed the same pattern excluding the colour calibration.
Luminance was combined with the RGB image using ImageBlend and noise was removed using NoiseXTerminator. Colors were given a little bit more emphasis by enhancing saturation using CurvesTransformation.
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.
BackgroundNeutralization was used to adjust the background level to 0.01, to align with other images. The final step in processing was a crop to taste. There were a number of bright stars in the original field of view, so it was decided to keep the nearest bright star in the image as part of the composition. So crop was applied having the galaxy a bit off-set.
Processing workflow (click to enlarge)
This image has been published on Astrobin.
