C27 Cresent Neb - Still learning to process

[Christopher Davenport]

Hello

About a week ago I had a nice clear spell, so I thought I would give my new modified DSLR a spin.

I sent my beloved 600D to Juan in Kent to be modified with a Baader filter replacement.

I started off by imaging M31 for about 2 hrs, and then thought I would grab a hour of C27 just for fun and to test out processing.

Well, M31 has turned into a marathon of processing that I just don't seem to be able to settle on a nice version of.

(alot of this has to do with trying to deal with noise from my DSLR.)

Anyway after messing about for a week with the M31 data, I have parked it until I can get more data and thought I should give the C27 data a crack.

I have recently downloaded some great PS actions for star reduction and thought this would be a good testing ground for it.

Anybody have some processing suggestion or comments on what you think of this would be welcome.

[glowingturnip]

Very nice !  Great star colour, and some nice detail in the crescent.

If I may - purely in the spirit of constructive criticism because this is a target I've been scared of attempting myself so far (all the good ones seem to have hours of Ha and OIII and whatnot, and maybe not for my dodgy DSLR) - but I think you're suffering from a touch of over-processing.

There's a lot of nebulosity around there, especially to the top right of your photo, but I think yours is just above your noise floor.  In over-stretching and in saturation to bring out the detail, that's what's brought on the granular look to the fainter nebulosity and given the blocky edges to the stars.

Maybe try another processing run, just focusing on bringing out the crescent and bright stars and letting the rest hint at their existence from the background ?  Try a little sharpening just on the crescent too, it can probably take it.

What denoising routines are you doing ?  There are a couple of great ones in Pixinsight - MLT and TGV, but I've not really seen anything convincing just using photoshop... and noise is the curse for us DSLR users...

Hope you don't take offence at my suggestions, believe me I've been there.  In fact I spent most of this afternoon trying to get rid of the noise in my attempt at the Eagle Nebula, so far not very well...

Have you got a weblink for Juan in Kent ?  I did think about getting my D80 modded but the only place I found was in the States.  I looked at the DIY instuctions, and I think definitely *not* to be attempted !  Mind you, my D80 is pretty shocking tbh, has a lot of amp glow, noise and the rest of it, so I might just treat myself to a nice Canon modded body for Xmas.

[Christopher Davenport]

Very nice !  Great star colour, and some nice detail in the crescent.

Have you got a weblink for Juan in Kent ?  I did think about getting my D80 modded but the only place I found was in the States.  I looked at the DIY instuctions, and I think definitely *not* to be attempted !  Mind you, my D80 is pretty shocking tbh, has a lot of amp glow, noise and the rest of it, so I might just treat myself to a nice Canon modded body for Xmas.

Hey Stuart,

I don't take offence to the crit, it's what I need. Strange how it is hard to see these things until somebody points them out.

Thanks, I was planing to reprocess after I got more data, but now I think I might give it a crack before.

My noise reduction is done in PS, three methods: (other than darks and or Cappa sigma stack in DSS)

1) Subtraction of gradient through Gaussian blur method

2.) Soft light layer of the nebula to accentuate signal.

3.) Noels actions, noise reduction techniques.

I use Image analyser to reduce noise as well.

Juans website -

http://cheapastrophotography.vpweb.co.uk

[glowingturnip]

ahh yes, that's the website I have bookmarked to look at biuying a new camera from.  Actually I think my existing camera's not really good enough, I might have to treat myself to a new modded one, and use the old one for terrestrial

[Astrosurf]

I think that's a lovely image. Yes, a tad noisy, but I have real trouble with noise and how to control it. I sometimes do a little G Blur on the red channel on a copy layer with a mask, and then bring through the detailed, un-blurred lower layer through the mask. I'm sure there's a better technique!  You've got great star colour there.

What's this 'soft light layer' you used?

Alexxx

[Christopher Davenport]

I think that's a lovely image. Yes, a tad noisy, but I have real trouble with noise and how to control it. I sometimes do a little G Blur on the red channel on a copy layer with a mask, and then bring through the detailed, un-blurred lower layer through the mask. I'm sure there's a better technique!  You've got great star colour there.

What's this 'soft light layer' you used?

Alexxx

Well, this is a trick which I stumbled onto in a photography magazine, for a completely different purpose, but it seems to work really well with certain objects in Astro.

Do a curves contrast on a copy layer and then set the layer to soft light, now play with the transparency and see what happens

Edit: now explore with this concept but using a over exposed stars from a mask, or a under exposed galaxy core.

[Astrosurf]

Sounds good! I'll give it a go.

[m37]

Lovely image which I would be more than chuffed with! I am no expert at processing but here are some thoughts.

Are you clone stamping/spot healing the larger stars and nebulosity out before blurring? Might be good if not.

Looks like you might be over curving a bit, make sure you anchor your curves for black/white points.

Use the levels at both extreme ends to find the darkest and lightest points and set markers.

Maybe try using multiple curves layers each with small adjustments, I often find this easier than trying to fit all adjustments into on set of curves

When subtracting skyglow with the Gaussian blur method, experiment with making the layer slightly transparent so you don't lose too much data, find the faintest star you want to see and stop once it is visible.

Don't be tempted to make the background too black

Duplicate the image and work on the nebulosity and stars separatelybthen mask one over the other

Just a few tips that have worked for me, that is a great image. I particularly like the range of star colours.

Cheers and look forward to seeing some more

Chris

[Christopher Davenport]

Lovely image which I would be more than chuffed with! I am no expert at processing but here are some thoughts.

Are you clone stamping/spot healing the larger stars and nebulosity out before blurring? Might be good if not.

Looks like you might be over curving a bit, make sure you anchor your curves for black/white points.

Use the levels at both extreme ends to find the darkest and lightest points and set markers.

Maybe try using multiple curves layers each with small adjustments, I often find this easier than trying to fit all adjustments into on set of curves

When subtracting skyglow with the Gaussian blur method, experiment with making the layer slightly transparent so you don't lose too much data, find the faintest star you want to see and stop once it is visible.

Don't be tempted to make the background too black

Duplicate the image and work on the nebulosity and stars separatelybthen mask one over the other

Just a few tips that have worked for me, that is a great image. I particularly like the range of star colours.

Cheers and look forward to seeing some more

Chris

Thanks for the advice.

I do tend to try do all curves in one layer.

I do noise reduction last after playing with stars. I will try other way round.

[Astrosurf]

Do you use Adjustment Layers or do you just open the Curves directly?

[Christopher Davenport]

I try to do everything through adjustment layers so I can blend transparency / move layer up or down, mask etc.

[Astrosurf]

Excellent. How do you blend? This is where I'm confused!

[Christopher Davenport]

Hope this image answers your questions.

[m37]

The reason I use separate curves layers is that any curves adjustment has an effect on the other layers. If you keep them separate you can keep the curve basically the same but using layer opacity you can reduce the amount of that layer and therefore the effect of that curve adjustment.

There is totally not a right or wrong way, when you get the results you want you have found the way to do it!

Cheers

Chris

[Astrosurf]

Hope this image answers your questions.

Thanks Chris, but it looks different from mine! If ever we meet up you can show me! Thanks for posting that.

[Astrosurf]

The reason I use separate curves layers is that any curves adjustment has an effect on the other layers. If you keep them separate you can keep the curve basically the same but using layer opacity you can reduce the amount of that layer and therefore the effect of that curve adjustment.

There is totally not a right or wrong way, when you get the results you want you have found the way to do it!

Cheers

Chris

You can make an adjustment layer affect only one layer buy holding down the Alt key when you click on the adj layer then ensure the checkbox is ticked (can't remember what it says!) Or you can hold down the Alt key when you click between that adj layer and the layer below it and it gives you the option to clip them together, giving a downward-pointing arrow. See here:

http://www.earthboundlight.com/phototips/photoshop-adjustment-layer-clipping-mask-layer-group.html

[Christopher Davenport]

Thanks Chris, but it looks different from mine! If ever we meet up you can show me! Thanks for posting that.

Different version, I am on PS5. Only version I know. Try google it for your version.

[Christopher Davenport]

Thanks for the advice.

[Christopher Davenport]

The reason I use separate curves layers is that any curves adjustment has an effect on the other layers. If you keep them separate you can keep the curve basically the same but using layer opacity you can reduce the amount of that layer and therefore the effect of that curve adjustment.

There is totally not a right or wrong way, when you get the results you want you have found the way to do it!

Cheers

Chris

It makes sense can turn effects on off or opacity up or down.

Will definitely start to separate these.

[m37]

I've also been playing with composite images from differently processe layers recently. E.g. if you want to emphasise some low lights and dust lanes then create a high contrast but otherwise fairly nasty version that looks pretty horrible but has well defined dark areas then drop it on top of the normal image, mask the dark layer out completely and use a soft low opacity eraser or white brush to bring the darker lines through for better definition. Needs to be done subtly but looks pretty cool.

Cheers

[Christopher Davenport]

Tried to reprocess, but not really sure if I got this better than the last time.

Anyway, bit sick of this one, so went out and tried a different subject to see if I could do better with more data.

[Astrosurf]

The first one is certainly better. You've brought in much more noise and the vignetting is very obvious. I have a big problem with noise and, for me, it's a pig to remove. Lots of lights is one of the solutions! For vignetting, I use GradientXTerminator in PS. But I'm sure you know about flats!

[Christopher Davenport]

The first one is certainly better. You've brought in much more noise and the vignetting is very obvious. I have a big problem with noise and, for me, it's a pig to remove. Lots of lights is one of the solutions! For vignetting, I use GradientXTerminator in PS. But I'm sure you know about flats!

Yip I know about flats and I know how to take out the gradient. Must say I don't mind these things, it makes if feel natural for me.

What kills me is the noise, I just hate the noise.

[Astrosurf]

Me too. It's the bane of my life. Roll on Lottery win and cooled Atik! Some people have made cooling units for DSLRs. Why not go onto the DiY section and ask??

[Christopher Davenport]

Me too. It's the bane of my life. Roll on Lottery win and cooled Atik! Some people have made cooling units for DSLRs. Why not go onto the DiY section and ask??

So I have done something around this, but been lacking in execution really.

I have a tec and power supply, with a tec temp controller from China. (£50 in total.)

Tested it all and I can get the tec down to -20C.

I was thinking of doing a cold finger, but it looks well technical, so now I am investigating a cold box with insulation.

Just have not had the time as this was supposed to be my project over the summer.

Any ideas on a box?