M27 Ha-RGB

[nucdoc]

 

 

I collected this data over the last two nights,  we have had a high pressure cell over us for the last week, the seeing has been the best I have seen since late winter. I collected 20 Min of each of LRGB, but when I add the L channel the image  becomes very pink,  I will have to revisit my processing and see if I can figure out why this is happening.

I collected the Ha as 2 minute subs, binned 4x4, I did this mainly because that was all the time I had left last nite, it actually gave the image quite a nice boost, however I do not have the proper darks and flats, do even after cosmetic correction you can see hot red pixels.  Will have to reshoot the flats and darks, either that or collect some 20 min 1x1 Ha subs next week

 

Mark

 

 

 

 

 

 

 

 

 

Imaging telescope or lens: Mead LX850 12 "AXCF Meade Telescope

Imaging camera: Atik 383L+ mono

Mount: Meade LX850 Starlock

Guiding telescope or lens: Mead LX850 12 "AXCF Meade Telescope

Software: PixInsight

Filters: Astronomik CLS CCD 2",  Astronomik Ha 6nm CCD,  Astronomik LRGB IIc

Resolution: 6576x4920

Dates: July 26, 2016

Frames: 20x300" 

Integration: 1.7 hours

Avg. Moon age: 21.12 days

Avg. Moon phase: 60.86%

Astrometry.net job: 1168097

RA center: 299.899 degrees

DEC center: 22.720 degrees

Pixel scale: 0.243 arcsec/pixel

Orientation: 179.927 degrees

Field radius: 0.278 degrees

Locations: Home, Toronto, Ontario, Canada

 

[swag72]

That's looking good  Well done. I think I can see a gradient in there though that could improve the over all image if dealt with

[PatrickGilliland]

Hi Mark

How are you adding your L channel for it to become pink it sounds like you are adding to Red channel?  As i see you have Pixinsight have you tired the LRGB tool.  Prepare a RGB and Lum image (stretched) open the tool, deselect RGB channel and add Lum file name to lum.  At the bottom select the noise reduction option, default is fine for first pass) drag the processing icon onto the RGB.

This will add the Lum correctly - it should not go too pink - if you find the image is skewed it is likely due to poor weightings.  Little trick here.  Extract lightness from RGB then linerfit your lum frame to that lightness one.  Then run LRGB combo on your linearfit(ted) luminance.  Weightings should now be closer.  You can also adjust weighting in the tool.  It's quite sensitive if you feel the lightness is too strong increase the setting by a factor of 0.05 - i think from memory its counter intuitive so you may need to slide left to go up (if that makes sense) have a play, you can adjust the overall l + RGB weights when used.

On the gradient issue try a Dynamic or even Auto background extraction on subtraction.  It is easily within the range of the tool, as Sara said if you get it right it should make M27 pop just a fraction more.

 

Paddy

[uhb1966]

A high pressure cell??? ah... Toronto, wrong continent!

PS superb photo!

[laudropb]

Very nice.

[ollypenrice]

I really don't see how Ha can work in 2 minute subs despite the binning. I kind of like 30 minutes... There is a very faint shell out there to go for...

Olly

[nucdoc]

1 hour ago, ollypenrice said:

I really don't see how Ha can work in 2 minute subs despite the binning. I kind of like 30 minutes... There is a very faint shell out there to go for...

Olly

Yes agreed, there is a very faint shell on the subs, but it does not show up in the composite.  Will need to wait for clear skies to try for proper Ha subs.  To my eyes, the Ha used on this images did add to the outer part of the shell, and on the right side, will have to post the plain RGB when I get home to show the difference

[nucdoc]

Sara, thanks for your advice, I did DBS on the master subs for each channel, but not after they were combined, so I will try that.

 

Paddy, thanks for your detailed tutorial, its looks like a couple of days of clouds so I will have some time to follow your suggestions

 

Olly, Below is the RGB without my very brief Ha, I guess the Ha really does not add very much given the way I acquired my Ha data, will try for more appropriate Ha subs when the skies clear

 

Mark

 

[nucdoc]

On July 28, 2016 at 04:59, PatrickGilliland said:

Hi Mark

How are you adding your L channel for it to become pink it sounds like you are adding to Red channel?  As i see you have Pixinsight have you tired the LRGB tool.  Prepare a RGB and Lum image (stretched) open the tool, deselect RGB channel and add Lum file name to lum.  At the bottom select the noise reduction option, default is fine for first pass) drag the processing icon onto the RGB.

This will add the Lum correctly - it should not go too pink - if you find the image is skewed it is likely due to poor weightings.  Little trick here.  Extract lightness from RGB then linerfit your lum frame to that lightness one.  Then run LRGB combo on your linearfit(ted) luminance.  Weightings should now be closer.  You can also adjust weighting in the tool.  It's quite sensitive if you feel the lightness is too strong increase the setting by a factor of 0.05 - i think from memory its counter intuitive so you may need to slide left to go up (if that makes sense) have a play, you can adjust the overall l + RGB weights when used.

On the gradient issue try a Dynamic or even Auto background extraction on subtraction.  It is easily within the range of the tool, as Sara said if you get it right it should make M27 pop just a fraction more.

 

Paddy

 

Paddy, thanks again.

Here is my first try following your directions, I extracted the lightness from the RBG and then linear fit my stretched Lum frame to the lightness frame.  I then used the LRGB tool to combine the new lum frame with the RBG frame, then background neut, color correction, DBE and some curves and saturation 

 

[PatrickGilliland]

9 hours ago, nucdoc said:

 

Paddy, thanks again.

Here is my first try following your directions, I extracted the lightness from the RBG and then linear fit my stretched Lum frame to the lightness frame.  I then used the LRGB tool to combine the new lum frame with the RBG frame, then background neut, color correction, DBE and some curves and saturation 

 

OK now you need to play around with the sliders until you get a good combo - probably not enough lightness in this one and RGB saturation taking over - just a case of tweaking the sliders until you find something you are happy with.

But you can see the difference - experiment a lot and it will all work out (my standard processing philosophy )

Paddy