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IC5146 - Cocoon Nebula

RichieJarvis

By RichieJarvis
in Imaging - Deep Sky

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RichieJarvis

RichieJarvis

Posted
Posted

Hi All,

I've finally added some colour to my IC5146 data from last week... *&^$& Clouds!

Details are:

Date: 2009-07-01 & 2009-07-09

Location: South Common Observatory

Scope: Celestron C8 at F/6.3

Camera: SXV-H9

Exposure (Ha): 19 x 600 seconds - 1x1

Exposure (OIII): 14 x 300 seconds - 1x1

Exposure (Hb): 7 x 200 seconds - 1x1

Guidescope: Astro Professional 102ED

Guidecamera: SX Guidehead

2009-01-09-IC5146-Ha19x600-OIII14x300-Hb7x200-process2-small.jpg

Thanks for looking!

Cheers,

Richie

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narrowbandpaul

narrowbandpaul

Posted
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i am sure someone has done it before Ian King, using two narrowband and a B filter is reflection nebulosity is present, eg M20

i would love to see the O[iII] frame from this image. I was under the impression that there was very little in IC5146...did you find this too?

great image though, Richie, great resolution.

paul

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GordonH

GordonH

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Hi Richie

This is a good result, you are quite right about there not being much OIII, I am not sure about the Hb as I don't use it, instead I use SII. As is often the case Ha is very dominant and for this reason you should keep your exposure times the same as Ha ie all exposures at 600 seconds and take more subframes (200 and 300 seconds isn't really long enough for emission line even with f6.3, I use 600 seconds for all my emission line even at f5), for example if you are imaging a nebula where there is a weaker OIII and SII component then keep the exposure length the same but take more subframes than for the Ha, this will allow you to push the OIII and SII more aggressively in the processing. Having different length exposures can lead to problems with balancing the colour. I think the cocoon nebula is not a very good subject for things like the HST palette but may be better suited for a LRGB with Ha for luminance and standard RGB for the colour, sometimes blending the Ha with the red channel

Best wishes

Gordon

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RichieJarvis

RichieJarvis

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Hi Gordon,

Yup - I normally do try and keep the dimmer emission lines at the same or longer - however, for this target, I had previously tried it, and detected no OIII emissions whatsoever - therefore the OIII and Hb were just to give colour to the stars really :)

Colour balance wise - I haven't done it with this one, but I tend to find blending the Hb and OIII 50/50 gives a much more 'real-life' type colour.

As far as using Ha/OIII/Blue - that works well for reflection nebulae, but the Cocoon is a pure Ha emission neb from what I can tell!

Cheers,

Richie

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GordonH

GordonH

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Hi Richie

Generally emission line filters are not going to work for reflection nebula which is why you don't see narrowband imaging of nebula such as M78, Iris nebula and so forth. As the cocoon is mainly Ha emission you may have been better off using RGB filters and combining them with the Ha which would have given a true colour image and also shorter exposure times with the RGB filters than with the emission line filters. This would also have given you the star colour that you are after. The cocoon nebula is one of those oddities that although an emission nebula it doesn't bring out very good results for tri-band emission imaging but better results can be obtained by combining Ha with RGB.

Best wishes

Gordon

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Tim

Tim

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Richie, I might be barking up the wrong tree, but I spent quite some hours on this target a little while back, and there is what seems to me to be some blue reflections in the area, and in the back of my mind I seem to recall reading that it had some reflection in.

Take a look at my result, you can see some evidence of it around the stars especially.

How did you get so close in btw? Would love to get in close like that!

http://www.btinternet.com/~mr.squeegee/Astro/CocoonNebula.jpg

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minimalist

minimalist

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Very nice Richie, very large scale and good detail.

I'm with the others, there is some very very faint reflection in that nebula, but I'd need many hours of data to even get there. I did image it last month, and if I squint hard enough I can see traces of it, but it's not a very good pic. I may post it at some point if I have nothing else more interesting.

But my congrats, this is a very faint object to image.

Daniel

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GordonH

GordonH

Posted
Posted
Richie, I might be barking up the wrong tree, but I spent quite some hours on this target a little while back, and there is what seems to me to be some blue reflections in the area, and in the back of my mind I seem to recall reading that it had some reflection in.

Take a look at my result, you can see some evidence of it around the stars especially.

How did you get so close in btw? Would love to get in close like that!

http://www.btinternet.com/~mr.squeegee/Astro/CocoonNebula.jpg

Hi

One of the problems with the reflection nebula is that in TJ's picture it is evident, but remember that was and RGB image using red, green and blue filters. Richie's image was taken with emission line/narrow band filters and they are not suitable for showing reflction nebula. They work fine for emission nebula, SNR and planetary nebula that have Ha, OIII and SII components but they do not work for reflection nebula. There are odd occasions where you can see 'the shape' of reflection nebula in narrow band shots (a good example of this is the small reflection nebula in the horsehead complex) but this is mainly due to the surrounding nebula showing it up. As far as I am aware the cocoon nebula is not the best target for tri-band emission line imaging as I mentioned earlier as you may get colour but you won't really be able to differentiate between the different components. As mentioned earlier though this target will benefit from HaRGB imaging

Best wishes

Gordon

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Tim

Tim

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Rob, you might know, :) how would it look to use Ha for Red, then G + B ?? Would it work, or look wierd?

I have a full set of filters now for the H9, the new ones from Baader (well, not Hb) so I am watching these type of posts carefully. In fact Richie, you are partly to blame for my recent outlay :)

I havent had any chance to use the rgb filters at all yet, i'm guessing they aren't so simple as the emission filters?

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RobH

RobH

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Hello Tim,

Using Ha for red, then green and blue, would be fine for the nebula but the stars will be odd due to the fact that they tend to be small in Ha.

I've used this method before, but I also shot some red subs and pasted the stars from the red onto the Ha to get them looking right.

Cheers

Rob

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