M33 advice please

[PeterBolt]

Hi, I took this image of M33 earlier in the month.  I was using an modified EOS 1000D with a Skytech CLS filter at ISO 1600.  I collected 12 x 10min subs to make the final image.  I noticed that I am not seeing the colours that I have seen in other photos taken with similar equipment and exposure.  Is there an issue with the way I am capturing the data or processing my images?  Any advice would be welcome as I am keen to learn ? 

 

[Incisive_Solutions]

Following for info

[PeterBolt]

So I've made a bit of progress.  I was struggling to remove the green hue left by the CLS filter when I first tried to process the image.  I have therefore added flat frames and adjusted the white balance using the Camera Raw Filter in PS.  This seems to have helped with the colours.  Any other advice / feedback would be welcomed.

 

[AstronomyUkraine]

@petedevon You have some good data there, the Ha is showing through quite well in the galaxy. The image overall still has a reddish caste to it, which needs dialling back a bit, as does the green. Using selective colour or using the target adjustment tool in colour mixer should solve that problem.

[PeterBolt]

 

@AstronomyUkraine many thanks for your comments, very much appreciated.  Are those tools you mention within the Camera Raw Filter menu?

I've had a play with the selective colour tool - do you think this is any better?  I found it hard to adjust the green caste without effecting the blue stars too much...

[AstronomyUkraine]

Posted by: @petedevon

I've had a play with the selective colour tool - do you think this is any better?

Looks a lot better now. The colour mixer is in camera raw, use the targeted adjustment tool on the green star, you have options in lum, saturation and hue. It will only affect the green colour.

[PeterBolt]

@AstronomyUkraine brilliant thank you so much I will take another look tomorrow ?

[PeterBolt]

@AstronomyUkraine I tried the targeted adjustment tool this morning and I think I have managed to remove the green caste now.  Thank you for your advice.

[AstronomyUkraine]

@petedevon Looks a lot better now.

[DaveS]

That's looking much better.

2 hours isn't a lot of data on this target unless you have a humongous telescope as the surface brightness is very low so you've done well to extract such a good image.

What's your sky like? Do you need that CLS filter which is eating your precious photons?

[PeterBolt]

@DaveS thanks for your feedback.  I am in the centre of a village and my backyard is surrounded by three LED street lights.  However the clear outside app says class 4 sky for my postcode. Do you think I would be better off without the filter?  I am using a 8" reflector F5.

[DaveS]

OK, Bortle 4 covers a wide range of brightness, but I'm thinking you should be able to get away with something less brutal than a CLS. What does CO give in SQI? I have 21.66 and don't need a LP filter.

With LED streetlights I would think that the IDAS D2 might be worth trying, as it's designed to cut out as much LED as possible without eating into the wanted signal too much.

You may even be able to go without a LP filter at all, worth a try if we ever get another clear night, remembering that a camera doesn't suffer from dark adaptation problems from streetlight glare.

[PeterBolt]

@DaveS it says 21.49.  I might try without the filter next time and see what happens.  I might need to save up a bit for the IDAS D2

[DaveS]

If you've got 21.49 that's pretty good, and I think well worth trying without a filter.

Those photons have come nearly 3 million light years, pity to block them at the last nanosecond!

[PeterBolt]

@DaveS good point!  I will give it a try.  I only started imaging a couple of months ago and there is so much to learn! 

[PeterBolt]

I decided to start processing the image again from scratch using the advice that people have kindly given me - I am much happier with the image now.  Thanks for all your help!