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Imaging Nebulae, missing color


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Hi,

I tried to capture some images of nebulae with my DSLR 1100D (non modded) and a Skywatcher 150pds with neodymium filter.

I am having trouble getting decent color out of my pictures.

I tried the cocoon nebula and with an hour of data, there was hardly anything to see.

Also the bubble nebula doesnt show much of the surrounding red region.

I have seen much better images of these objects with even shorter exposures.

Does someone has some pointers why this is so?

My own research shows that a Ha Filter might help, but thats once again 200 euro's I am not willing to spend right now.

Thanks in advance,

Mike

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With an unmodded DSLR you will struggle on objects that are strong in Ha, IIRC you are losing 80% of the light at that wavelength due to the built in colour correction filter in the Canon,plus only 1 in 4 pixels are recording Red light (due to the Bayer pattern), and I think the efficiency of the chip is lower at Ha too. From my experience with the Bubble its tricky to get good data at sensible exposure times without modding the camera. I tried this with my 6" newt and unmodded 450D and got pretty much the same result a few years ago. I plan to try it with the now modded 450D next clear night :)

Hth

Keith

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It looks ok to me, i would say you just need more sbs, and maybe a longer exposure time.

The gradient can be removed, but i also thing you have over stretched the image in the post processing. It is a faint object, you just need more data. You need to remember you have an unmodded camera, so you will not get as good results as a modded or CCD. But you can get very good results with what you have just need more data as i said.

A Ha filter will not work if your camera is unmodded, it will be a pointless purchase, they only come in to their own when it is modded or you have a CCD. It also helps if you can get to a really dark site.

Have you taken darks to remove the noise?

HTH

Keiran

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Thanks guys,

Yes, I use darks. This pic is maybe a bit to much processed, yes..

I was also considering that it is so because of the unmodded DSLR, but I read that DSLR's that are unmodded are not that bad as people think in the Ha region.

Thats why this question arose.

So accoording to you guys, more subs, modding the DSLR (which I wont do..lol) or a CCD camera

Have some things to think about now..

Any reccomendations for a decent CCD is also welcome! :)

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You haven't gone all the way with your present image, yet. One way to pull more of the reds in Ps is to go into Image, Adjust, Selective Colour and then, in the reds control, move the slider towards cyan. This often makes the Ha pop.

You have far too much green in there and it has a heavy gradient. Adjusting it in levels (getting the top left of the peak to line up with the red and the blue would be a start.) Then you could download Hasta La Vista Green, a freebie on Rogelio Bernal Andreo's website. Google Deep Sky Colors (American spelling.) This, like SCNR in Pixinsight, is a remover of unwanted colour noise. This green gradient is likely to plague all your images. It even happens with CCD.

A good way to boost colour without boosting noise ( a problem with the normal Saturation slider) is to put the image into Lab colour mode and, in both the a and b channels (but not the L), push up the otherwise numpty contrast tool to about 30. (Never touch it for anything else!!)

There is a lot of Ha around the Bubble but, apart from a bright central block, it is pretty faint.

Longer and more subs? But of course!

Olly

Edit, while you are in Lab colour mode, which you should swap for RGB when done, you could try some hefty noise reduction on the a and b channels as well. The detail will be held by the L channel much as is the case with Luminance in LRGB imaging.

Edited by ollypenrice
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That looks alot better, add some more data when you get the chance and you will be well away.

ps: Weird, but I can't seem to find the edit button for my posts here on SGL

You cant edit your post until you are an advanced memeber

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A good way to boost colour without boosting noise ( a problem with the normal Saturation slider) is to put the image into Lab colour mode and, in both the a and b channels (but not the L), push up the otherwise numpty contrast tool to about 30. (Never touch it for anything else!!)

Olly, do you do the above in levels/curves? I

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