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Image post processing expectations


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I posted this thread on an imaging forum and got no response so trying again on beginners. Help would be hugely appreciated.

I am new to astrophotography.

I haven’t mastered auto guiding yet (long story) but I will do eventually.

However, I am getting some single images, that as a beginner, I am encouraged by.

I am subtracting Darks and stacking lights in DSS (limited to total of 10 – 20 mins total exposure at the moment as I am too impatient).

I have done loads and loads of background reading on post processing in Photoshop.

What I have still no confidence in, as I get such varied results, is whether I am reaching anywhere near the potential of these images with my post processing.

I have noticed people on the Forum taking other peoples shots and improving them.

I am being cheeky and directly putting a plea our for someone to have a go at one or more of my shots straight out of DSS to see what they can do with them with a view to me realistically setting expectations on my efforts.

Examples from the weekend just gone that I could provide include

Rosette Nebula

Horse Head Nebula

Eskimo Nebula

M35 + NGC2158

M38 + NGC1907

How do I best make the images available to the forum, the DSS output *.tif files are approx 95Mbytes?

Thanks again.

Steve.

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A few tips.

1 For heaven's sake don't post images over 2-3MB. Leave them as 16 bit TIFFs but cut down the pixel size. If the worst comes to the worst post them as high quality jpegs.

2 Don't be impatient. You will very soon find that 20m exposures barely allow you to get more than just plain old noise.

3 You would be best off posting the Rosette as it is the brightest you have imaged.

Dennis

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Ok Steve I had a bash at the Rosette. I have to say with just 15 mins of data I was pleasantly surprised to get this much detail out of it.

I have done very little work on the stars just a little bit of reduction and raised the colour slightly. The background is a bit murky I think though its to be expected with such a low signal to noise ratio.

Regards,

Dave Moulton

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Dave,

I am gobsmacked. Thank you very much.

I don’t have photoshop on my work computer. At home tonight I will *.jpg and shrink my best effort and post it to this thread. A long way off yours as you will see.

I expected red from all the images I have seen of the Rosette yet I am getting predominantly green. Plus as I bring out the detail via curves and levels my stars go big and fuzzy (good technical terms those…) while you have managed to send them the opposite way. Can you please give me a clue how you achieved that?

It has done exactly what I hoped and that is give me renewed hope and enthusiasm.

Thanks again,

Steve.

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Ok Steve I had a bash at the Rosette. I have to say with just 15 mins of data I was pleasantly surprised to get this much detail out of it.

I have done very little work on the stars just a little bit of reduction and raised the colour slightly. The background is a bit murky I think though its to be expected with such a low signal to noise ratio.

Regards,

Dave Moulton

That's from 15 minutes of data with an unmodded DSLR? WOW!

Looking forward to some tips on how this was achieved...!

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That's from 15 minutes of data with an unmodded DSLR? WOW!

Looking forward to some tips on how this was achieved...!

This was a bit tricky with such weak signal due to the limited data, also the colour was a bit skewed.

I increased the star colour using noels actions before stretching

I then stretched the histogram twice and set the black point and then used the selective colour tool mainly under the neutrals to restore the colour balance a little.

Star size was then reduced slightly see below

Using Noels actions Bright star select then select , modify, expand 3 pixels

then filter, other, minimum and then fade minimum to set the star size. Brilliant routine for reducing star bloat after stretching

I then selected the Nebula inverted the selection and applied some noise reduction to the background then reversed the selection and applied a slighly less aggressive amount of noise reducion to the Nebula

HTH

Dave

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Mark,

Your version is very similar to the very best of my attempts but yours is better as yours stars are smaller. How did you keep the stars small?

Apologies for not posting my processed version yet, I will get there, the reasons are 'complicated'.

This is an unmodified DSLR image with no filters involved. What I don't understand is all the green. I now have a better idea of how to turn it red thanks to Dave but doesn't the fact that it comes out green mean it is green? I know this sounds daft in that everyone knows the Rosette Nebula is red (don't they?) but it seems it wasn't the night I took the pics? The same night the Horsehead came our red.

Mark, thanks very much for spending the time on it, much appreciated

Steve.

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Steve -

Sorry it took me so long to take a look at them. Things have been crazy busy lately. I had a quick stab at them and these are the results. You would definitely benefit from more subs to increase your signal to noise ratio. As they are right now any amount of stretching makes the noise nearly overwhelming.

Anyways - hope they are to your liking.

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post-24627-133877544451_thumb.jpg

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Anna,

They are tremendous, thank you very much. It helps enormously to know what can be achieved when setting my own expectations.

Skies permitting in Ibiza next weekend I hope to start guiding and also intend making myself concentrate on a single target rather than impatiently jumping around. So much to see though!

Next 'problem' is deciding on that target. Nice problem to have though.

I really fancy a galaxy but don't think I have the focal length (resist it...) for the galaxies in prime position at the moment.

Thanks again.

Peace & love,

Steve.

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