Go Back   IceInSpace > Equipment > Astrophotography and Imaging Equipment and Discussions

Thread Tools Rate Thread
Old 26-06-2019, 06:00 PM
Slawomir's Avatar
Slawomir (Suavi)
Registered User

Slawomir is offline
Join Date: Sep 2014
Location: North Queensland
Posts: 3,238
Combining 4 narrowband channels in PixInsight

Hi all,

Last night I tested the Lagoon for NII data and it looks sufficiently different from Ha, OIII and SII that I am tempted to dedicate a clear night to collect NII data and then to use all four channels for a narrowband composite.

Is there a neat way of combining 4 channels in PixInsight into one image, so that all four contribute colour information?
Attached Thumbnails
Click for full-size image (Lagoon HaNIIOIIISII.jpg)
158.0 KB63 views
Reply With Quote
Old 26-06-2019, 06:15 PM
codemonkey's Avatar
codemonkey (Lee)
Lee "Wormsy" Borsboom

codemonkey is offline
Join Date: Jul 2013
Location: Kilcoy, QLD
Posts: 2,056
That's pretty cool, Suavi.

I have no answers for you, but I'm interested in seeing what others have to say.

Seems like it'd be nice to somehow build a luminance from the normalized masters weighted by the amount of local contrast in a given area... not sure how one might achieve that but it sounds like a good idea :p
Reply With Quote
Old 26-06-2019, 06:30 PM
Atmos's Avatar
Atmos (Colin)
Ultimate Noob

Atmos is offline
Join Date: Aug 2011
Location: Melbourne
Posts: 6,907
Not sure if it would work but if you input NII into both red and blue it would make a violet.
You’d have to potentially Max() function it in though.
Reply With Quote
Old 27-06-2019, 09:01 AM
Andy01's Avatar
Andy01 (Andy)
My God it's full of stars

Andy01 is offline
Join Date: Mar 2012
Location: Melbourne
Posts: 3,002
Could be done in Photoshop with 4x hue/saturation layers, not sure about PI - be interesting to see what you come up with!
Reply With Quote
Old 27-06-2019, 04:22 PM
rcheshire's Avatar
rcheshire (Rowland)
Registered User

rcheshire is offline
Join Date: Apr 2010
Location: Geelong
Posts: 2,627
Would the LRGBCombination module do it? Substituting channels?
Reply With Quote
Old 27-06-2019, 09:06 PM
Slawomir's Avatar
Slawomir (Suavi)
Registered User

Slawomir is offline
Join Date: Sep 2014
Location: North Queensland
Posts: 3,238
Thank you all for your suggestions. I have not yet collected the data for the 4th channel for the Lagoon and was interested in what can be done with 4 narrowband channels, and whether itís a worthwhile practice. And now itís cloudy again with rain...
Reply With Quote
Old 28-06-2019, 10:14 AM
AstralTraveller's Avatar
AstralTraveller (David)
Registered User

AstralTraveller is offline
Join Date: Mar 2008
Location: Wollongong
Posts: 3,699
That is a very interesting project. I'm not even sure I have heard of NII filters - I'll have to read up on that.

I also can't offer any solution but I can offer a shameless plug for the "PixInsight: More Advanced Topics" workshop at the upcoming NACAA - it sounds as though you could skip the introductory workshop. PixInsight is just one of a variety of workshops to be held over the weekend.

BTW We will be making more announcements once the chair of the Program Committee returns from the TSE in Argentina!

Cheers and Clear Skies,
Reply With Quote
Old 02-07-2019, 08:03 AM
Slawomir's Avatar
Slawomir (Suavi)
Registered User

Slawomir is offline
Join Date: Sep 2014
Location: North Queensland
Posts: 3,238
Thanks David for the info

I have decided to try another target for four narrowband channels and attached is a screenshot of 4 single subs of M20 in Ha, NII, OIII and SII.

SNR in those subs is in the ratio of about 4:2:1:1 (Ha:NII:OIII:SII).

I nearly have enough Ha for this image, and pondering on which two I should collect to combine with Ha. Given enough clear skies, I may try collecting all four.

One advantage of getting NII is a possibility of integrating it with Ha for a synthetic Lum and increasing SNR in the LUM, and NII also nicely shows fainter nebulosities around M20, while SII has a weak signal and OIII does not show any gaseous structures surrounding M20, so I would probably not try adding them to the synthetic LUM.

Any advices and opinions will be highly appreciated.

Attached Thumbnails
Click for full-size image (M20 four channels.jpg)
203.2 KB35 views
Reply With Quote
Old 03-07-2019, 08:06 AM
troypiggo's Avatar
troypiggo (Troy)
Bust Duster

troypiggo is offline
Join Date: Nov 2008
Location: Brisbane, Australia
Posts: 4,845
G'day Suavi,

I recall from way back in 2012 there was a processing challenge posted by Vicent on the PI forum. He had data from something like 23 images/filters. There were a few guys who posted their take, but the most in-depth was, not unsurprisingly, from Juan. He posted a detailed breakdown on his approach. Not sure if it'll be directly translatable to your narrowband data, but might give you some ideas.

I also got to thinking about RGB vs CMYK. Perhaps you could assign a filter to the CMYK and combine along these lines?
Reply With Quote


Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT +10. The time is now 03:59 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
Limpet Controller
NexDome Observatories
Astronomy and Electronics Centre