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Leo Triplet (M65, M66, NGC 3628)

Dec 2011 - March 2012

The Leo Triplet consists of three bright galaxies that appear in the same field of view.  The triplet was always a favorite visual target, but it is amazing how much more detail you can see with astrophotography.

The images below show the triplet four different ways. 

Color Enchanced with H Alpha

Color Enhanced with Hydrogen Alpha

click for a larger image


"True" Color Image

Luminance colored using RGB

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Leo Triplet in Luminance


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Leo Triplet in Hydrogen Alpha

Hydrogen Alpha

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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.

Map Overlay

Processing Details

The images were processed with PixInsight. 

420 sec
900 sec
300 sec
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300 sec

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

LT area map
LT detail map

Area Map

Detailed Map

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Copyrights for Photos

Creative Commons License
Except as noted, all work on this site by Robert J. Hawley is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License. This permits the non commercial use of the material on this site, either in whole or in part, in other works provided that I am credited for the work.