The Seagull and the Wild Duck

[Russ.Carpenter]

Here is an interesting part of the Southern Sky. The big nebula is the Seagull Nebula (IC2177), which has been imaged about a million times. The little one is the Wild Duck (NGC2357). It's not common to capture both birds in a single field of view.

This image was made with a Nikon 200mm lens, F2. The camera is a an FLI Microline 16200 CCD Camera, 6mm pixel. I used all three narrowband channels and tone mapped them with the marvelous "matrix" tool in the Color module of version 1.7.421. It's impressive that StarTools now allows you to play with tone mapping options so late in the process.

I guess nearly all fast camera lenses have some chromatic aberration. That's true of the Nikon, too. I used the quick and dirty solution of desaturating the entire star field, but I soon want to learn more sophisticated ways of dealing with the flaws in this lens. Chilescope spent some big bucks acquiring the Nikon (around $5,700) and I need to figure out how to process its images correctly.

Earlier this year I posted the same image to Astrobin, processed with PixInsight. StarTools was more effective in several aspects, especially unblocking the midtones. Yay, autodev!

Russ

[admin]

I used all three narrowband channels and tone mapped them with the marvelous "matrix" tool in the Color module of version 1.7.421. It's impressive that StarTools now allows you to play with tone mapping options so late in the process.

As with most PI alumni, it's always a pleasure watching someone use ST to its full potential and fundamentally understanding the innovations ST brings to the table.

I guess nearly all fast camera lenses have some chromatic aberration. That's true of the Nikon, too. I used the quick and dirty solution of desaturating the entire star field, but I soon want to learn more sophisticated ways of dealing with the flaws in this lens. Chilescope spent some big bucks acquiring the Nikon (around $5,700) and I need to figure out how to process its images correctly.

Depending on how the nature of the aberration (it's a little hard to tell from the small image), there are various techniques you can employ. You can indeed fix the stars after the fact (The Filter module's Fring Killer feature was made for this), use the Shrink module, deconvolve the out-of-focus channels before compositing (YMMV with this one), or decide to use only the in-focus channel(s) for your luminance while using all channels for your coloring (the perks of processing luminance and chrominance separately keep on giving! )

Do let me know if you'd like me to expound on any of these (though as said, a higher res image would help determining the best way forward).

Also, if you find a busy star field is detracting from the object of interest, consider using the Life module's "Isolate" preset (set by default when you launch it) to refocus energy on the larger scale structures in your image (it's a specialized version of a Wavelet Sharper that accentuates very large structures in lieu of smaller details such as stars and noise). Another method is to use the Shrink module (just updated and now works while Tracking is on too).

Beautiful work!

[happy-kat]

another trick I use for chromatic aberration is to exclude by use of a mask the stars that are large when using the colour module. The chromatic stars are generally not the interesting coloured stars so by excluding them they are left as luminance and don't bloat blue. Any stragglers missed could be fringe killered in the filter module.

[Russ.Carpenter]

Hi happy-kat,

It was generous of you to share your promising ideas for taming the stars. I'll mention that I did use isolate (another remarkable ST innovation). Without it, the star field was overwhelming. Meanwhile, I'll be experimenting with unruly stars.

In your experience, has the lens module been useful in a situation like this?

Russ