Leo Triplet (M65, M66, NGC 3628)

Dec 2011 - March 2012

• Lower Right - This is a processed Hydrogen Alpha Image.  Note how much more prominent the bar is in M66 than in the Luminance Image
• Lower Left - This is the image produced by a Luminance (clear to Visible Light) filter.  It is a map of the intensity (but not the color) of the image
• Upper Right - The R, G, and B filters are combined to produce a RGB image.  This image is lower quality than the luminance image, but it only used to assign colors. The combined image is processed until you have a finished, stretched, noise removed, and sharpened image. The RGB image is then combined with the L data to form this image. Since the L image is higher quality (more, longer exposures) it contains the finer details and will be used for the brightness of the final image.  The RGB contains the color (more properly Chrominance).  This image represents a "true" color image of the galaxies.
• Upper Left - The Red data is combined with the H Alpha data to form "Rh". This highlights those portions of the returns that are high in Hydrogen without destroying the color of stars or red from cooler stars.  The Rh is combined with G and B to form a new RhGB Chrominance.  The RhGB is then used to add color to the Luminance forming the LRhGB image.  Note how the dust lanes in NGC 3628 and M65 are now more prominent. Note also the clumps of star formation in M66.
  

Color Enhanced with Hydrogen Alpha click for a larger image	"True" Color Image Luminance colored using RGB click for a larger image
Luminance click for larger image	Hydrogen Alpha click for larger image

Active Map

In this image I overlay a map generated by SkyMap Pro with a larger crop of the Luminance Image. Click to see the full size image.  It is easier to see the small galaxies in the larger version.

Processing Details

The images were processed with PixInsight. 

Of course this is only what met the image quality standards.  The luminance data can only be collected on a clear, moonless night. The Halpha data was generally collected when the moon prevented L or RGB data from being collected. This winter I have had several nights where I discovered that high clouds were present which resulted in low quality images. All of the affected images had to be tossed.

The color data was fairly low quality (especially the Blue), but after processing I decided it was good enough. Originally I was going to process the color data as HDR, but problems with the low duration images plus lack of any stars with interesting colors made me decide to just use the long exposure.

The key lesson learned in this image was how to add the H alpha data.  Instead of using a Max function I used the scaling procedure described on Harry's Shed.  This was superior to the other techniques I have tried since the Ha exposures are so different than the Red exposure.  The scaling allowed me to get the desired effect. Since the H alpha shows a large general return I left the galaxies slightly red colored instead of removing the Ha signal as described in the video.

I also started using the masked stretch script.  This seems to prevent the stars from blowing out as much as a simple HT does. Note the difference between the LRhGB image and the L image.

Map of Leo Triplet

Area Map	Detailed Map click for larger image

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