Post Processing Help Needed - Please

[PatrickGilliland]

Hi All

I was wondering if any of you may be able to provide me with some assistance on my first attempt at CCD imaging and the processing of the images.  M27 was the subject.

The following image is HOS based filters to RGB.  (No flats or bias as yet as just testing and finding my feet)

2 x lights @ 4 and 6 minutes - each calibrated/dark removed (same duration for darks), then stacked and debloomed.

I then stacked @ 1:1:1 and image looked as follows with no further editing.

I also stacked a version with no darks for comparison which looks as follows.

I actually prefer the nebulas colours in the version without darks.

My issue is, allowing for the fact with HOS I am expecting some artificial colours is that the images are very red saturated  - especially the stars many of which have red halos.

Despite spending all day yesterday trying different stacking ratios and colour adjustments I can not get rid of red stars or halos effectively.

The best I got was by reusing the H channel and mixing as luminance into a LRGB stack as follows.

So can anyone advise on what I should be doing to get rid of halo's and redness in images or point me in the right direction.  Very frustrated especially with the halos. 

Hopefully you more experienced people will see what I have done wrong and point me in the correct direction.

Thanks

Paddy

[swag72]

Hi Paddy - Normally the colour combination is SHO - That will get you the more traditional colours that you see.

[PatrickGilliland]

Hi Paddy - Normally the colour combination is SHO - That will get you the more traditional colours that you see.

I thought that was the hubble palette? I tried this - same issues just with green instead of red, even I go for 2:1:2 on SHO to RGB

[ollypenrice]

Whichever palette you choose I think the logical starting point would be a neutral background sky, so that would be my first step in balancing. I'd use the Ps colour sampler eyedorpper to read the background values in various places then clip the black points in order to get all channels the same. I don't do pure NB imaging so if this didn't work I'd just try to make it look neutral. The top two have red backgrounds, for instance.

Your red haloes presumably just come from the fact that you have more signal in red. Options;

You could try running Noels Actions Make Stars Smaller just on that channel.

You use a star mask to protect the stars of the red channel during the stretch. (You'd have to stretch it before combining.)

You could make a copy layer, make a star selection generously larger than the stars and well feathered, then go to the red channel in Curves, pin the background sky where it is, then pull down the curve above that keeping an eye on the haloes which should pull down OK.

Then go to the top layer and, where this is worse than the modded bottom layer, erase it.

Olly

[steppenwolf]

Your Green channel is the one with the best detail, the red channel looks a little harsh and is perhaps a little soft on focus.

I have taken out your red channel to work on in isolation and reduced its contrast followed by a gentle sharpening and then re-assembled the image. To remove the halos, I selected the stars using the 'colour range' tool from the 'Select' tab in PS3 and reduced the saturation level. Finally a gentle curves lift to get some more of the planetary nebula detail to show. Not my finest work, just a 'down and dirty' quick process but I hope it addresses some of your issues:-

[PatrickGilliland]

Thanks Olly and Steve,

Really I am not sure on best route/workflow or even software!  I have looked into tips above and will play around with them shortly.

Should I be attempting to edit the mono images before I combine this is something I have not tried?

Happy to play around all day with images but unless I have followed the correct process there is a chance I will never get a image worth the effort.

To recap.

1. Calibrate each image with its corresponding dark.

2. Stack H, O and S images (1x4 and 1x6 Mins).

3. Colour stack H, O, S @1:1:1

Result is red saturated image with red stars and halos.

What other steps should I be adding to the process above.  What software would help me with each of the above or any new steps?

Feel like I was close for my first effort, yet so far still lol.

Paddy

[PatrickGilliland]

Er hold fire on any further advice, just realised I was sent a 35nm Ha not a 7nm!  Probably explains some of my issues so will get that sorted before I try anything else, thanks for your time so far!!

[steppenwolf]

Aha, that would very much explain why the OIII channel was so much better than the Ha !!