Red Cast

[BobJC]

So this question pops up many times I'm sure.

I'm currently on a work vacation 🤔 and cashflow is a bit tight. I have been imaging with my regular Nikon D500 unmodded and 200-500 zoom lens. I want to image nebula which I can't do with my current set-up. So, the new (10 year old) kid on the block is a Canon 600D off EBay which I've successfully ripped (Carefully removed) the U/V filter out of - The HA mod. First target - the Heart & Soul Nebulae which has turned out ok in the end, but was a real problem to process. I guess I just need to learn new techniques.

The issue is, with the modded Canon I'm starting off with a strong red cast across the stacked image. I want to take the next step to better results and an easier processing journey. Having checked out the options, I'm thinking of going with the Optolong L-ENhance clip-in filter which I believe will instantly solve all my light pollution, red cast and extended processing woes with one sprinkling of its magical fairy dust.

Am I right, or does someone need to take me to one side and slap some sense into me?

[Starwiz]

1 hour ago, BobJC said:

I'm thinking of going with the Optolong L-ENhance clip-in filter which I believe will instantly solve all my light pollution, red cast and extended processing woes

A light pollution filter can make a big difference if you're in an area polluted by sodium lighting.

Two images from some years back when I was using a modified Canon 1200D.  The Orion Nebula, an easy target was without the CLS filter.  The Horsehead, a much fainter target, was my first image with the CLS filter and I was amazed what a difference it made.  Previously when I'd tried the Horsehead, it was washed out by the light pollution.

John

[Budgie1]

How are you stacking the images?

If you're using DeepSkyStacker (DSS) then try this:

• Open DSS and go to Settings in the Options menu.
• Click on "Stacking Settings" then the "Light" tab.
• Under "Stacking Mode" check what's selected, most likely "Averaged", then try the likes of "Median" or "Kappa-Sigma". I found "Kappa-Sigma clipping" with the standard settings removes the red cast from my modified EOS 1300D, as well as removing satellite trails as well.

[ollypenrice]

Colour gradients appear in almost all astrophotos, even those from very dark sites like mine. Many of the dedicated software astro packages have tools for dealing with them. Pixinsight has ABE and DBE, Astro Art has gradient removal, APP has a tool, and so on. There's also Gradient Xterminator, a plug-in for Photoshop.

Olly

[BobJC]

1 hour ago, Starwiz said:

A light pollution filter can make a big difference if you're in an area polluted by sodium lighting.

Two images from some years back when I was using a modified Canon 1200D.  The Orion Nebula, an easy target was without the CLS filter.  The Horsehead, a much fainter target, was my first image with the CLS filter and I was amazed what a difference it made.  Previously when I'd tried the Horsehead, it was washed out by the light pollution.

John

Thanks John, I didn't realise a CLS filter would make such a difference to a modded camera.

[BobJC]

50 minutes ago, Budgie1 said:

How are you stacking the images?

If you're using DeepSkyStacker (DSS) then try this:

• Open DSS and go to Settings in the Options menu.
• Click on "Stacking Settings" then the "Light" tab.
• Under "Stacking Mode" check what's selected, most likely "Averaged", then try the likes of "Median" or "Kappa-Sigma". I found "Kappa-Sigma clipping" with the standard settings removes the red cast from my modified EOS 1300D, as well as removing satellite trails as well.

Hi Martin,

I'm working on Mac and have been doing everything in Affinity Photo. I've just tried Siril for my latest heart Nebula shot and this produced a much better result in the colour calibration. May try this method in future. I do find that having come away from Windows some years ago does seem to restrict my options with this hobby.

[BobJC]

Update - I have found an option in the Affinity Photo stacking process to use the Master Flat for white balance calibration. This seems to remove most of the red cast in the earlier stack

[AstroGee]

there are some good straight to the point affinity tutorials for astro here:

https://affinity.serif.com/en-gb/tutorials/photo/desktop/video/512549746/