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The other night I took 100 20 sec subs of m42 with my 1000d and 10" auto tracking Dobsonian (alt/az).  I'm struggling to get the processing right, trying not to blow out the core but wanting to bring out as much detail as possible. I've done 2 versions but am not sure which is best.

Please tell me A or B?

A

post-4016-0-88480200-1420057414_thumb.pn

B

post-4016-0-24290700-1420057498_thumb.pn

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Both versions are best - and you can have the best of both using Layers in Photoshop. While this tutorial uses subs of different length it will work perfectly well for two different stretches of the same data, one a gentle stretch and one a hard one. In your case I'd suggest an even softer one than the first image blended with a harder stretch than the second.

http://www.astropix.com/HTML/J_DIGIT/LAYMASK.HTM

M42 is a special case in which this technique is vital. While it is often suggested that all sorts of targets need it, this is simply wrong. The technique is rarely needed. But, yes, M42 needs it big time!

Olly

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Cheers Olly thanks for that link! I shall have a crack at combining the 2 images when my head has cleared from last night lol

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Nice images. I have been experimenting with layering 3 different exposure times with good success. I have not experimented with more than 3 though. Maybe someone with more experience can recommend just how many different exposure times are worth layering before the point of diminishing returns. 

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I use layers all of the time in PS to ensure that brighter parts of a nebula don't get out of hand. 

I stretch the complete image, duplicate the layer and create a layer mask on the top duplicate layer. I 'reveal' the layer mask and then using the brush tool I use varying opacities to bring the darker area in from the layer below to the brighter area in the upper duplicate layer. This ensures that nothing gets out of hand.

So while there are no different exposure lengths, the principle is very similar.

Hope that makes sense!

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Thanks guys I really need to knuckle down and get to grips with layer masks. I assume all this can be done on CS2?

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I've knuckled down and used a layer mask in cs2 to combine the images. Must say I'm surprised how easily the blended.

post-4016-0-13573100-1420664672.png

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Hi,

It is a very nice image and your large number of subs has resulted in a very clean data set. It is short but clean so it can stand a bit of heavy stretching. I made this from the 2nd version just to show what there is. Hope that you approve.

Regards,

A.G

post-28808-0-41600200-1420674000.png

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Thanks guys very interesting repros! That extra stretch is a real eye opener Lensman! Looks like I need to combine 3 different layers to get the most out of the image.

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The brighter your colour data is the more easily it can burn out the colour. To some extent we can see this in your blending which, from a brightness rather than colour point of view, is spot on. What I think would make it even better would be a boost to the colour saturation in the bright Trapezium layer. Once AG gave it some welly on the stretch we saw the shortage of colour in that region.

Olly

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I've started from scratch and come up with this version. Not sure about the colour....maybe overdone the saturation?

post-4016-0-22961700-1420836479_thumb.pn

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what does your histogram look like with this image? I think it needs a balance as it looks like it will have a quite heavy skew in either blue or green. Balance that up and that will look better I would think.

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Thanks Sara you are correct the green needed bringing down :

post-4016-0-45382600-1420841771_thumb.pn

Edited by Space Cowboy
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I've used an artificial flat to combine with the image. Think it looks better?

post-4016-0-74017100-1421270252_thumb.pn

Edited by Space Cowboy

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