Is it possible to remove CA from this picture?

[pixueto]

I've been working on a picture I took last Saturday with an old 200mm lens. The lens is a cheap second hand one and creates a fair amount of cromatic aberration. I was wondering if there is any technique that I can use to correct the colour of those stars affected. In photoshop?

Thank you

[Keiran]

You could try using the selective colour tool in photoshop, and removing that colour from the image.

The image looks great though. Its nice to see them two together in the same image.

Keiran

[Gina]

Very nice image Bit too small to see any problem though. I also think the green level could do with correcting as the background looks green. Could you post a bigger image please?

[laser_jock99]

Post up a larger image and I could check what's possible?

[steppenwolf]

The CA can certainly be improved. I used the colour noise filter in PS at 50% to give a better balance to the stars and then adjusted the green hue to a more natural background colour:-

[VigdisVZ]

Nice composition, what focal length is that you're using?

[Chris]

Thats great pixueto, as said its framed nicely with all the nebs together, I'll be giving this a go with my Canon USM 70-210 lens, once piggy backed.

[mgirdwood]

nice wide image.

i hope you dont mind a quick play with levels and curves on the ipad.

[pixueto]

Thank you for your comments.

Very nice image Bit too small to see any problem though. I also think the green level could do with correcting as the background looks green. Could you post a bigger image please?

laser_jock99

Post up a larger image and I could check what's possible?

There you go. Thanks

[pixueto]

The CA can certainly be improved. I used the colour noise filter in PS at 50% to give a better balance to the stars and then adjusted the green hue to a more natural background colour:-

Thank you.

[pixueto]

Nice composition, what focal length is that you're using?

I'm using an old soligor 200mm F4.5 lens on a canon 450D unmodded with a CLS clip filter. 1hour 6 mins. Subs: 10mins, 8 mins, 4 mins, 1 and a few of 30, 40 and 50 seconds. Darks, flats and bias.

[Cloudwatcher]

If you click on Auto Colour in PS the green tint will vanish from the image.

Having done that it appeared to show up faint nebulae,wether real or artificial I'm not sure but played with the hue/saturation and colour balance which gave me this............

[laser_jock99]

A quick go in Adobe Photoshop Elements

1) Click on auto colour correction to get a black back ground

2) Two iterations of reduce star size (Noels Actions Pluggin)

3) Tweak of curves to reduce dark area noise

Overall I don't think there was a lot of chromatic abberation. The main problem I could see was large stars maybe due to being slighty out of of focus or selecting to wide an apperture?

[pixueto]

Thank you all. Yes, I think the image is slightly out of focus as I had to heat the lens because of the dew and I didn't refocus. I think for that lens some targets are better than others. For instance, the cygnus complex doesn't come up very well (maybe because there are too many stars) but this one seems to be fine.

[Cath]

Isn't Chromatic aberration where the colour channels don't properly line up with each other?

Looking at the posts, you guys are talking about Colour Balance rather than Chromatic aberration?

[steppenwolf]

Isn't Chromatic aberration where the colour channels don't properly line up with each other?

Looking at the posts, you guys are talking about Colour Balance rather than Chromatic aberration?

You are right about CA, Cath but this image shows both issues - the red halos around the stars are indicative of the CA and the green hue is a colour balance issue.