›

OSC and Dual Band processing

Neil Schulman
in PixInsight
I wanted to post and see what people are doing with their dual band processing. Maybe compare notes and share ideas on ways to maximize the data.

What I do today for emission nebulae is to capture as much dual band (L-Ultimate in my case) and then an hour or so for RGB stars. As of today my typical workflow would be: Gradient Correction, SPCC, BlurX, then remove the stars from the dual band image and separate the stars from the RGB.

Then I’ll stretch the RGB stars to taste and saturate as seems appropriate and set aside. On the dual band I work with it as is. Since it is HOO by definition it doesn’t strike me as worth it to try to extract the Ha from OIII. So I’ll use GHS however many times to stretch the nebula, sometimes HDRMT, and then run NarrowbandNormalization to exaggerate the colors. I’ll then do some contrast adjustments to taste. Then I’ll screen the stars in and call it a day.

I know many things are personal opinion and to taste but I’m curious what other people do and whether I can learn from it.

On galaxies I do separate the Ha out and do a continuum subtraction and add it to the rgb before stretching. I feel like there may be potential in the OIII captured but I don’t try to use it currently. I separate the Ha using a formula I ran across instead of just using the R channel.

Anyway, just wanted to share…

Comments

  • Neil Schulman
    I guess I’m the odd duck here on this one :)
  • Zachary Patten
    Thanks for sharing; I do mostly DSO and capture Ha to augment it as there are many on YT that suggest this.  That being said I haven't really sorted out a method for augmenting the LRGB image with this data yet (at least nothing I have been happy with).  I'd be interested if you could expand on the specific processes/steps you are using to add the Ha data.

    While I have a lot of the basics down with PI I still have much to learn; could you expand on what the "continuum subtraction" is you reference?
  • Zachary Patten
    I answered my question about the continuum subtraction after reading another post linking to the videos covering it.  I'm not subscribed to Horizons yet; however I plan to so I'll cross that bridge at that point.

    I'm still curious to hear more details about how you approach integrating the Ha data however as well as other possible methods you've explored and what the results were.
  • Neil Schulman
    What I have tried (based on several different tracks and tutorials):
    1. Separating the Ha from the dual band and then using PixelMath to do a simple addition to the rgb
    2. Same as above but after stretching and using a combine with op_screen in PixelMath
    3. Adding the DB and Ha while unstretched to the unstretched rgb and then re-running SPCC
    4. Doing the continuum subtraction and then combining back to the rgb right before stretching

    Number 4 was what got me the best result. The way I get the Ha out of the dual band is a pixelmath formula I ran into a year or so ago. It tries to approximate the spill over across the different channels since there's overlap in an OSC for different wavelengths:

    To get the OIII I run this on the DB file: (2*0.9*((G-0.11*R)/0.917)+0.5*((B)/0.12))/2.3 with R, G, B being the separated channels.

    For Ha I run (R-0.03*Oiii)/0.8

    It seems to work nicely. It is not that different than just extracting Ha with the R channel, though.

    For the subtraction and re-combination I use the scripts from (PI Repository Link) https://www.ideviceapps.de/PixInsight/Utilities/

    You can do the same thing with NBColorMapper and some cleverness but I find the other scripts to be a lot simpler.
  • Neil Schulman
    FWIW you can see the results of it in the galaxy pics on my Astrobin like this one of M101: https://www.astrobin.com/260jtp/D/, M81: https://www.astrobin.com/7a39t2/G/, and M31: https://www.astrobin.com/rdysxf/D/
Sign In or Register to comment.