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M42 - What a difference Darks and Flats Make

johnb

By johnb
in Imaging - Deep Sky

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johnb

johnb

Posted
Posted

Taken with Skywatcher Explorer 250 and Cannon 450D (unmodded)

50 x 60 Secs Unguided, 20 Darks, 20 Flats

Im really happy with this image (seem to have finally cracked it), couple of questions

1 - My 450D is unmodded is that why it seems a little bue ?

2 - Am i going to see a difference if I get another 50 Mins and add to it ?

3 - Im still quite new to Levels and Curves so guess there may be plenty more data in this image - if anyone feels like seeing if thats the case that would be great.

Regards

John B

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sixela

sixela

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err wow - what did you do

John B

Something I personally don't like.

First, it makes everything quite artificially red, but losing information --you're losing the nice contrast in hue between the main OIII foreground wings and the H-alpha inside--, and secondly, the blacks are clipped and a lot of very fine detail at the edge is lost (of course, it's that detail that is noisy, but hiding it is something I don't like).

I like the original better, frankly. A lot. In fact, if you'd posted the second image, many people would have asked for your raw and produced the first one :). If you want more colour, simply try increasing the saturation or playing just a wee bit with gamma.

but it's very personal, of course. Some people like overprocessed and in-your-face contrasty images, I don't, and I find the harsh almost painted stars on the suppressed blacks really grating. Grey is good. If you have pixels that are "0"-valued, then you've gone too far, because the sky background actually isn't black.

What extra subs will give you, by the way, is even less noise in the very faint and whispy detail on the left and round M43. So you'll have less inclination to sweep it all under the carpet.

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sixela

sixela

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All feedback apprecaited, any comments on my questions ?

Yes, it's indeed a bit light on the red because of the standard "IR"-filter on the Canon (try to use a channel mixer and play with the red channel a bit, but not too much), and extra exposure time stacked with this will mainly reduce noise in the fainter parts (but M42 is really quite bright in the middle, so you already have a fairly good S/N ratio there).

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RobH

RobH

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I agree with Sixela about the first image being better, and for the reasons he's given.

Personal taste is one thing, but heavily clipping the black point shouldn't be done.

Your first image is very nicely processed....a bit odd in colour due to the IR filtering, but otherwise fine.

Try playing with colour balance, and 'selective colour' in photoshop and see what you come up with.

Cheers

Rob

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cardconvict

cardconvict

Posted
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i also agree clipping the black point looks to me so wrong it i ok to have a little bit of noise in the back ground than have the black point clipped, because all your hard work collecting the photons just to cut them out in the processing does,nt seem wright the first image looks great if you can i would mod your camera

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Luke

Luke

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Lovely shot, John, magical! Personally I think it looks really cool with the limited colour here.

1 - My 450D is unmodded is that why it seems a little bue ?

I'm not sure why you're not getting more colour, I've been having a go at imaging M42 using an unmodded 450D and I've been surprised at how much colour is coming through, it was more than I was expecting? :)

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Steve 1962

Steve 1962

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Personally I think your first image is a corker John - good focus, nice and smooth with loads of suble detail - very natural looking.

The subdued colour gives, in my opinion, a realistic impression of how M42 looks optically so that's not a bad thing at all.

I've had a 1000d modded back in the summer and if your 450d is anything like my 1000d - you'll get a load more colour if you mod it.

More time will further reduce any noise in the image, so you may be able to pull more faint stuff out but if I understand these things rightly - by doubling the total exposure time you'll only reduce the noise for the sq root of two for where you are now.

No harm having a go though!

Steve

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sixela

sixela

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the best i could get your colour seems week im not sure why i had to use saturation alot to get this amount of colour data

[ATTACH]46930[/ATTACH]

That's actually very good, but it screams for a mask based on luminance for that colour rebalancing (where you keep the original colour where the luminance is high). M42 in the centre is always saturated, and so changing the balance there will make it a tad unnatural (yellow in this case). Othet than that, the colour is spot on (of course there's a bit more noise in red, but that's because of the camera filtering - can't magically reconstruct the photons that have been filtered).

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dlp

dlp

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I've found I get exaggerated blues on my Nikon unless I set white balance manually to about 5.5k rather than rely on 'auto'. Maybe some help?

I know you can change it on the 'Camera Raw' dialogue (or whatever software you're using), but that's another step in an already long processing chain.

David

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