Ngc 300

[pvelez (Pete)]

Continuing my experiment adding Ha to LRGB galaxy shots, I added an hour of Ha to NGC 300.

This is a fainter target than others I've attempted recently. I comprises 54x300s L, 4 x 900s Ha and 18x300s each RGB. Taken with QSI 583 on RC8.

I have a colour gradient in the background that I'm finding hard to remove - LP I guess. I plan on collecting another couple of hours L tonight to try and get the SNR in the galaxy up so I can drop the black point a bit to even the background. If anyone has any PI suggestions, I'd appreciate them.

Thanks for looking

Pete

[cometcatcher (Kevin)]

That looks great. I love the embedded Ha nebula.

[RickS (Rick)]

Coming along nicely, Pete. I'm surprised that DBE won't deal with the gradient. I've had some success with masking galaxies and applying different amounts of stretch to the galaxy and the background.

Cheers,
Rick.

[alpal]

Hi Peter,
I had a go at reprocessing the small file that you uploaded.
I masked out the galaxy & worked on curves in the background
including a fake luminance layer.
What do you think of that?

I am sure I could get the background better with the full size tiff.

[pvelez (Pete)]

Originally Posted by alpal

Hi Peter,
I had a go at reprocessing the small file that you uploaded.
I masked out the galaxy & worked on curves in the background
including a fake luminance layer.
What do you think of that?

I am sure I could get the background better with the full size tiff.

Thanks for that. Its certainly an improvement.

What do you mean by a false luminence layer - is that a mask? I suspect its similar to the technique I've been using in PI

I've been using Channel extraction to create a new luminence layer, clipping the black with Histogram Transform, applying it as a mask, inverting it and then playing with the Histogram Transform tool to bring down the black. I hadn't thought of using Curves instead to beat down the noise in the background.

I'll have another play tonight. I collected another hour of L last night so I can add that too.

Pete

[alpal]

Originally Posted by pvelez

Thanks for that. Its certainly an improvement.

What do you mean by a false luminence layer - is that a mask? I suspect its similar to the technique I've been using in PI

I've been using Channel extraction to create a new luminence layer, clipping the black with Histogram Transform, applying it as a mask, inverting it and then playing with the Histogram Transform tool to bring down the black. I hadn't thought of using Curves instead to beat down the noise in the background.

I'll have another play tonight. I collected another hour of L last night so I can add that too.

Pete

A fake liuminance layer means that - in photoshop CS5 -
I converted you colour pic to gray scale.
I then made an inverted layer mask & adjusted the sliders to mask out
the bright areas such as stars & the galaxy. (ctrl L)
I then worked on the background with curves to darken the background.
I then used this as a new layer with a blend mode set to luminosity
to enable adjustment of the colour image.
I also played with contrast & HDR toning.

All of this should be done with your actual luminance data
not a fake luminance that I played around with.

I always divide my image into 3 layers.
(1) stars
(2) galaxy or nebula
(3) background.

I work on each separately & then combine them.
Also - with background problems.
Make a new stack with all processing set to median -
that really helps - but use that extra stack only in the background layer.

cheers
Allan

[cfranks (Charles)]

I'm only part way through my data collection for this object so I can't help much but I have noticed it seems to require longer than normal (for me) exposures. My Ha and Luminance both have improved with 1200 second exposures (obvious really!) so I will get some more tonight hopefully. RGB is still to be attempted. It is a great looking object and you are heading for a nice image.
Charles