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Heart Nebula, different...

Shibby

By Shibby
in Imaging - Deep Sky

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Shibby

Shibby

Posted
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I thought I'd go back to my Heart Nebula data to reprocess. I'm glad I did; I think I must have processed the colour data with my eyes closed last time, it was awful! This time, I've taken a bit more care, carefully bringing up all the details while controlling the stars as best I could.

For this attempt, I decided against boosting the red channel too much with the Ha layer, instead using Ha only for luminosity (70% ish). Normally you'd expect this to wash out all the colour, but I have come to realise that if you process the Ha and the colour to the same levels, all the colours from the colour layer are pretty well maintained. (Last time I pushed the Ha way too far, the colour not enough).

So this has resulted in a (perhaps unusual) version that emphasises all the colour variation throughout the nebula, rather than being pushed to the limits to drag out all the faint bits. I personally

much prefer the contrast that is maintained. I'd be interested in your opinions? (original version here: http://stargazerslou...1789-the-heart/)

Ha: 66x600s ISO-800

Colour: 23x240s ISO-800

Extra star colour: 18x120s ISO-400

Camera: Canon 450D, modded

Scope: Skywatcher 150PDS

Mount: Vixen GP

Guiding: Orion mini finderguider + SPC900 webcam (unmodded)

The combined result:

gallery_5051_1080_267384.jpg

The Ha layer:

gallery_5051_1080_23661.jpg

The colour layer:

gallery_5051_1080_1395772.jpg

Detail:

gallery_5051_1080_699293.jpg

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davew

davew

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Just to buck the trend, I'd say that although the first post was a bit " Full " this is sparse. No nice soft fiddly bits. I like soft fiddly bits !

A cross between the two would be my choice. Good detail non the less.

Dave.

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Shibby

Shibby

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Thanks for the comments :) Always interesting to hear the different opinions! I just wish I could work out what approach I personally like best so I can move forward with it on the next image! :icon_scratch: I think you might be right, Dave. Perhaps if I pushed this one a little further I would arrive at a happy medium between the two.

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VigdisVZ

VigdisVZ

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This is an amazing picture!

I am fairly new at this and I have just ordered a 150PDS. I am very curious to know what mods are made to your DSLR and how you set it up to get the different stacks (like the HA layers that I understand is hard to get without a CCD camera with filter).

Keep up the good work!

Carl

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Ags

Ags

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This is an amazing picture!

I am fairly new at this and I have just ordered a 150PDS. I am very curious to know what mods are made to your DSLR and how you set it up to get the different stacks (like the HA layers that I understand is hard to get without a CCD camera with filter).

Keep up the good work!

Carl

Hi Vigdis,

I am far from expert, but I will try answer your questions. A DSLR usually has a red filter that cuts out most of the far red and near infrared. This means the camera is not sensitive to the deep red light emitted by hydrogen - so-called Ha light. You can get your camera modified to remove the factory filter so you get three times the sensitivity to Ha light - an exposure for 1 minute with a modded camera gets as much light as 3 or more minutes with an unmodded camera.

Modding does not increase sensitivity in the green and blue sections of the spectrum, so modded and unmodded cameras are equally sensitive to Hb light and OIII light. Hb is emitted by hydrogen so you might ask why bother modding your camera for Ha? The reason is that Hb is one third as bright as Ha in the typical emission nebula.

Another popular wavelength is SII, but this is very faint and deep red, so you definitely need a modded camera to get any SII light.

Just like with CCDs, to capture narrowband images with a DSLR you have to put a narrowband filter in the optical train.

Finally, all this talk of modding and narrowband imaging is only relevant to emission nebulae. Modding and narrowband filters are not relevant to photographing most galaxies, star clusters, reflection nebulae or dark nebulae.

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Shibby

Shibby

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Sorry for not responding sooner. Thanks again for the comments! :)

I am very curious to know what mods are made to your DSLR and how you set it up to get the different stacks (like the HA layers that I understand is hard to get without a CCD camera with filter).

Agnes has pretty much covered everything I think! I performed the mod myself, replacing the original colour balance filter with a Baader clear glass replacement (you only really need to this if you want to retain perfect AF e.g. for daytime photography). As Ags says, this makes the camera more sensitive the Ha emitted from emission nebulae. You can use the same filters you would use with a CCD, but in the case of Ha (and SII), you're only making use of the red pixels on your sensor so you effectively lose resolution. So far, I've only tried an Ha filter (Baader 7nm) but plan to give OIII a go in the future.

The Ha subs are stacked separately to the full colour ones (taken with just a light pollution filter.) I then combine these 2 layers in Photoshop. Hope this helps!

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VigdisVZ

VigdisVZ

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Thanks for sharing your knowledge Agnes and Lewis. It feels reassuring that my soon-to-be setup has the potential for fantastic images like these. I'll be back for more pro-tips once I'm comfortable with basic operation. Not sure down wich camera path I'll go (not sure if I want to mod my DSLR, not sure if getting another DSLR, not sure if CCD etc) but information like this is crucial for coming to a decision.

Keep up the good work!

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