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M42 and Horsehead attempt

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Hi All

Here's my attempt at M42, needs lots of work.

I have more data, shorter subs etc. Please could someone point me in the right direction for a tutorial on combining different exposure lengths for greater dynamic range.

This is 8x4mins iso800.

There are links to the TIF's if anyone wants a go.


Horsehead 5x12mins iso800. This one is a nightmare to PP for me.



Edited by GrantEb
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Hi, I am by no means an expert at combining images, and in fact I've never actually tried it, so I'd kind of like to see what the forum experts have to say.

However, I have read a few tutorial on this (link below). The general idea is to use your longer exposures to create a sub-stack that will be used to bring out the detail in the fainter parts of the image (i.e. the nebula). However, when you stretch this, the bright core will saturate and all detail will be lost. Thus, the shorter exposures will be used to create another sub-stack that you'll stretch to make the bright core look decent.

What you then do is bring the two images into photoshop and place them on separate layers, with the longer exposures toward the back. Working only on the back layer, you have to create a mask that selects only the overexposed parts of your background (i.e. the core). You then apply this mask to the top layer and select a blending mode so that photoshop effectively replaces the overexposed core in the lower layer with the nicely exposed core in the top layer.

Here is the link to the tutorial, which explains it much better than I can. It has pictures also.

Compositing 2 Different Exposures via Layer Masks

Hope this helps and I'd like to see what sort of results you come up with.


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Hi Grant - I had a look at both of your tifs, hope you don't mind me commenting as as you know I'm no expert.

M42 - the core is pretty much burnt out. I think you need to utilise your shorter exposures in the stack. Also very noisy - no darks?

HH - again very noisy, no darks?

Quite pronounced gradients on both - no flats?

For a little bit of work doing the darks/flats I'm sure you could improve them no end!


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It is a good start but when making images available for others to have a go at please don't do any processing on it. I spent a few minutes in PS and applied high pass, a rotation (to North up) and noise reduction with Neat Image. It was then re-sized (1200 pix high) and jpegged down to 206kB. Colour was re-balanced and the dodgy edges cropped off.


edit: the roiginal looks a lot better than this on my monitor. Web colours interfering again.


Edited by roundycat
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