Image Type: |
Monochrome |
Constellation: |
Draco |
Telescope: |
10" Aries f/15 Maksutov-Cassegrain on Astro-Physics 900GTO German Equatorial |
Object: |
SAB(r)b Galaxy |
Focal Length: |
2642mm |
Distance: |
120 million light years |
Resolution: |
0.53"/pixel (imaged) |
Dimensions: |
5.5'x3.0' |
Accessories: |
Moravian G1-0300 as Off-Axis Guider, 0.67X Astro-Physics CCD Telecompressor |
Magnitude: |
11.87 |
CCD: |
QSI 532wsg, running at -20 deg. C |
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Exposures: |
25x5 min |
Aries MCT in Malvazinky Observatory |
Filter(s): |
Astrodon Clear |
Exposure Date: |
25-26 May 2011 |
Location: |
Malvazinky Observatory in Prague, Czech Republic |
Seeing, FWHM: |
1.7" |
Processing Software: |
MaximDL, PixInsight, Photoshop |
Image Acquisition Software: |
MaximDL, TheSky6, CCDAutoPilot, FocusMax, PinPoint |
Remarks: |
Shot with 33% central obstruction baffle which successfully minimized all the stray light and flat field problems (as with NGC 5907). Stacked and calibrated in PixInsight. No deconvolution was used because SNR was low.
PixInsight:
* Calibrate using Vincent Peris procedure.
* Register.
* Batch debloom in MaximDL and integrate in PixInsight. (PI lacks deblooming tool.)
* Automatic Background Extraction to remove gradient.
* Clone image, mild Histogram Transform on the clone, generate star mask, delete clone.
* Histogram transform on the main image.
* Wavelet HDR to bring dark structure out - without star mask.
* A Trous Wavelet Transform with K Sigma Clipping to reduce noise (with star mask).
* Re-use NGC5907 GRADIENT mask to perform corner erosion: fix stars at the very corners. (Camera tilt?)
Photoshop:
* Levels, denoise faint galaxy outer arms.
* Resize (smooth gradient).
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