Starship Asterisk*

Adam, I just love your picture of NGC 3938! This galaxy is one of the "textbook-magnificent" face-on spirals, but it is too rarely photographed. You do it splendid justice with your fine resolution of it and your wonderfully rich palette of colors!

Ann

Ann wrote:Jaime Fernández, I can't quite make head or tail of your NGC 410 image. Is it a narrowband image or an RGB? It looks like a narrowband image, but the stars are nicely multicolored, and many of them are really blue, the way they would only be in an RGB image. Many of the details in the nebulosity show up so well that it may take a narrowband image to make them look like that. It's certainly a very nice "combination" of a narrowband and an RGB image (if that is what it is).

Hi Ann, it's a pure narrowband image, there is no RGB on it. Thanks for your kindly words.

The full process details for this picture are as follows:
1.- Captured using standard methods and techniques. Three days narroband images, Ha (Baader 7nm), OIII and S2 (Baader 8nm). Note: some days later I discovered my f/4 telescope was out of collimation during these shots (!).
2.- Separate calibration, registration and integration of each set of shots using PixInsight Core 1.6. Standard masked histogram stretch for the resulting three images. All further process was done with PixInsight Core 1.6.
3.- PixelMath using the following formula (from PixInsight forums):R = 0.5*S2 + 0.5*Ha ; G = 0.15*Ha + 0.85*O3 ; B = O3
4.- Masked curves adjustment.
5.- High Dynamic Range Wavelet Transformation (HDRW) on 2 layers over a copy of Ha image obtained in step 2. ACDNR masked noise reduction applied. Masked Morphological Transformation (erosion), applied only to stars to reduce its size.
6.- LRGBCombination, using the modified Ha image obtained in step 5 as Luminance at about 90%, and narrowband color combination obtained in step 4 as chrominance. Chrominance noise reduction applied. Lighness and saturation slightly adjusted.
7.- Masked curves adjustment and ACDNR final masked noise reduction applied.

This is not a silver bullet nor is expected to be a perfect processing technique, but it's what I did and hope this help to anyone to give a try on their narowband shots.

Regards,
Jaime

NGC2403
MyWebSite: http://fth.bounceme.net/
Copyright: Fred Herrmann

Ann wrote:Adam, I just love your picture of NGC 3938! This galaxy is one of the "textbook-magnificent" face-on spirals, but it is too rarely photographed. You do it splendid justice with your fine resolution of it and your wonderfully rich palette of colors!

Ann

Thank you Ann. In terms of color... there is an interesting (because I do not know exactly what it is) green blob at the top of the galaxy in my image. It isn't an error as it appears in an older image I captured of this galaxy. Perhaps it is a Wolf-Rayet nebula in NGC 3938. Maybe just a metal poor HII region or, more exciting, a supernova remnant. It is stellar in my image... so it is hard to get excited about- but a mystery nonetheless. I hope someone can follow-up on it.

Regards,
Adam Block

Horse Head Portrait
MyWebSite: http://fth.bounceme.net/
Copyright: Fred Herrmann