Narrowband Rosette-Pixinsight

Master Files

We have almost 25 hours of data from Starfront Observatory in Texas. It breaks down like this:

Halpha-45 x 500s
OIII-65 x 500s
SII-65 x 500s
RGB 24 x 30s each.

After pre-processing we have 6 master files. Here are the narrowband masters:

Master Ha

Master SII

Master OIII

RGB Stars

Before dealing with the narrowband data, I'll combine the red, green, and blue masters into a single RGB image, remove any gradients, and then color calibrate. Click here to see those steps in more detail applied to a different image.

Next, I run Blur Xterminator to correct star shapes and Seti Astro's Star-Stretch script to stretch the image. A dose of Noise Xterminator and a pass of Star XTerminator, set to Unscreen Stars, gives me a stars-only image I can use in Photoshop.

Background Extraction

Normally, I use Graxpert for gradient correction, but I'm not happy with the uneven result it produced, so I'm going old school and using PI's Dynamic Background Extraction process.

I brighten the image temporarily using STF and place a few sample points in areas that look like dark sky background. Relaxing the shadows and raising the smoothing factor generates a fairly smooth gradient, which seems more appropriate.

Graxpert worked well on the OIII and SII masters.

You'll need to look closely to see the yellow sample points.

The corrected image. It's hard to see the difference on the web.

The removed gradient and DBE Tolerance, Shadows and Smoothing settings.

Xterminator Time

Now it's time to exterminate things. Typically I wait until an image is stretched to use Noise XT and Star XT, but lets try something different: Blur, Noise, and Star XT before stretching.

First, Blur XT for a little deconvolution (sharpening). The correct stars feature shrinks them enough, so sharpen stars is 0.00.

Nonstellar sharpening at 0.80 gives a nice, natural look.