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M76 Little Dumbbell Nebula


gorann

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An HaRGB image I processed of this little cutie tonight from data from the Liverpool Telescope. The following filters and subs were used (90s is an approximate mean of 60-120s subs):

Bessell B 33 x 90s
Bessell V 28 x 90s
rdss-r 42 x 90s
Ha 18 x 120s
So totally about 3.6 hours of data from this 2 m RC telescope, which is more data than I usually am able to gather from their data base - must be one of their favorites

Stacked in Nebulosity 4 and processed in PS CS5

All comments most welcome! (but you may not get an immediate response since I think I am off to bed now).

LT M76 HaRGBNyPS20sign.jpg

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13 hours ago, Galen Gilmore said:

That's absolutely superb! Nice job!

 

13 hours ago, johnfosteruk said:

Outstanding. 

Thanks Galen & John. Much appreciated!

The first version was without any deconvolution and sharpening (well, almost), so this morning I had a go at that to see what I could get out of it. Hopefully, the details it brought out were are all there but hidden in the data. I am sure that some (Wim?), maybe most, think I have gone a bit over the top but then you can just look at the first version. Myself I am not sure, possibly a mix of them would be better, and I tried that but somehow I get addicted to seeing the details and feel a loss when I see the image becoming blurry if I mix in the first un-sharpened version.

Well, here it is and any comments are most welcome.

 

LT M76 HaRGBNyPS27sign.jpg

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Great image, Göran. Even the second version :D I like the tight stars and crisp detail in that version. You are right, it makes v1 look blurry.

This image is also extremely free from noise. Due to the abundance of data?

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7 hours ago, simmo39 said:

That is a stunning image!

 

4 hours ago, Jeff-Colorado said:

Lovely image!

 

33 minutes ago, wimvb said:

Great image, Göran. Even the second version :D I like the tight stars and crisp detail in that version. You are right, it makes v1 look blurry.

This image is also extremely free from noise. Due to the abundance of data?

Thanks guys!

yes I like it more and more. Looking around on the net I just cannot find an RGB (or HaRGB) image of this resolution, and not even in NB since Hubble does not seem to have imaged it (but maybe someone knows - I just used Google). I think it comes down to the rare occasion that over two years, this 2 m scope was imaging this object rather often and I could download a total of 3.6 hours of data. So even with a lot of aperture, data counts, as Wim pointed out! Most large scopes probably do not spend that much time on one object.

However, there is one other image from LT data on M76 on the net, posted on Astrobin by Paddy:

http://www.astrobin.com/179589/B

It is a very beautiful winner image and it has about the same level of detail (maybe more) but the colours look very different and I am lost at figuring out how we could end up with such different results.

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4 minutes ago, Davey-T said:

I like sharp images of some subjects and this is one of them.

I did one a while ago but never finished it and my colours are similar to yours.

Dave

Thanks Dave!

I found this site which also shows images rather similar to mine except at the ends of the nebula, but probably the large amount of Ha data I got from the LT (added 50:50 to the red data) explains the nice details I get from the ends protruding on each side of the blue center:

http://www.messier-objects.com/messier-76-little-dumbbell-nebula/

This is what the LT Ha data looks like:

LT M76 Ha comboPS1.jpg

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The LT scope has much more light gathering power, and in order to capture the faint outer edges of this little gem with ordinary gear, you need a long (single frame) exposure time. Thus target has a huge dynamic range.

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2 hours ago, wimvb said:

The LT scope has much more light gathering power, and in order to capture the faint outer edges of this little gem with ordinary gear, you need a long (single frame) exposure time. Thus target has a huge dynamic range.

Nice image Dave! (especially for being a "normal" scope)

Yes, I think this is what Olly's refers to as the f-ratio myth. Aperture do count even if the image is taken with the same f-ratio. I just used a field of view calculator to find out if the image is taken at f/3 (Camera in place of 2nd mirror) or f/10, and it actually is at f/10 which means a focal length of 20 m. The reason the nebula still fits in the frame is that the CCD chip is 6 x 6 cm (15 um pixels). I think the camera itself also explains some of the sensitivity. This is not an ordinary off-the-shelf astrophoto camera.

15827456612_6359081932_o.jpg

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15 hours ago, gorann said:

 

 

Thanks guys!

yes I like it more and more. Looking around on the net I just cannot find an RGB (or HaRGB) image of this resolution, and not even in NB since Hubble does not seem to have imaged it (but maybe someone knows - I just used Google). I think it comes down to the rare occasion that over two years, this 2 m scope was imaging this object rather often and I could download a total of 3.6 hours of data. So even with a lot of aperture, data counts, as Wim pointed out! Most large scopes probably do not spend that much time on one object.

However, there is one other image from LT data on M76 on the net, posted on Astrobin by Paddy:

http://www.astrobin.com/179589/B

It is a very beautiful winner image and it has about the same level of detail (maybe more) but the colours look very different and I am lost at figuring out how we could end up with such different results.

Hi Gorann

I did a Ha-o111rgb version of m76 back in 2014, In fact it is actually in the deepsky showcase 2014 thread. I used a C11xlt and an atik 314l camera with baader filters. I did bin 2x2 as I was having to do 20+ minute exposures @f10 and on a neq6 was quite testing. Its great to see this gem of a PN back in the spotlight so very well done on your image!

M76 little dumbell.jpg

M76 The Little Dumbell.png

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This objects turns out to be a real challenge. Of course I had to download the data (limited to only one exposure time per filter), but the dynamic range of this little devil is off the charts. Like @PatrickGilliland, I lose colour in the core, whenever I try to tame it. And adding the Ha destroys the colour balance overall. I'm at the steep end of the learning curve of HaRGB processing.

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1 hour ago, wimvb said:

This objects turns out to be a real challenge. Of course I had to download the data (limited to only one exposure time per filter), but the dynamic range of this little devil is off the charts. Like @PatrickGilliland, I lose colour in the core, whenever I try to tame it. And adding the Ha destroys the colour balance overall. I'm at the steep end of the learning curve of HaRGB processing.

What have i done wrong now :) Here is my version http://www.astrobin.com/179589/B/?image_list_page=4&nc=&nce= there is some colour there and realised some of it.  My new manual HDR approach would likely realise a lot more colour now - quite astounding how much more detail and colour it reveals.  See my M81 post and the NGC 2903 going up shortly.

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18 minutes ago, PatrickGilliland said:

What have i done wrong now :) Here is my version http://www.astrobin.com/179589/B/?image_list_page=4&nc=&nce= 

You published a fabulous image, which we now relate our (in my case, pathetic) processing attempts to. The only remark one can have to that image, is that it lacks colour in the core, where others have it. This is probably due to hdr compression on high intensity data. I've seen your development from then to your latest M81 image.

This comes to mind :wink:

749956.png.f4b5056bc03a8cc808a6b54aed3167c8.png

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1 minute ago, wimvb said:

You published a fabulous image, which we now relate our (in my case, pathetic) processing attempts to. The only remark one can have to that image, is that it lacks colour in the core, where others have it. This is probably due to hdr compression on high intensity data. I've seen your development from then to your latest M81 image.

This comes to mind :wink:

749956.png.f4b5056bc03a8cc808a6b54aed3167c8.png

 

It might be interesting to try it out.  Take colour image, small stretch, increase the stretch and bump up the saturation a little.  Repeat.  I find about 7 increases from very dark to just beyond max brightness with v5 being the master target version.  You then simply layer the darker versions with more colour masked over the top of the areas with less colour [lost through brightness increase], careful to match the luminosity though as you do.  V6 and 7 you use in RGB only if they show anything not on v5 (for Lum this would equate to the wispy fine detail so not always relevant to RGB).

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Maybe I should explain a bit how I did the M76 processing (all in PS), which may explain why I managed to retain colour in the core (maybe it was also cheer luck and I may not be able to repeat it if I tried again:icon_biggrin:).

I stretched each colour channel separately (except that I mixed sdss-r and Ha 50:50 from start). I did about 10 smaller stretches before I felt satisfied with the dynamics of the image in the channel. When I stretch I always use the "Select Color Range" sampler in PS to mark the brightest parts and then inverse the selection (making a mask over the brightest parts) and then do a careful stretch, making sure I do not blow out any bright areas and avoid sharp transitions against the masked areas. The first selection usually only includes some bright stars but I make a new selection before each stretch and this selection then becomes slightly bigger every time (as the image becomes brighter and brighter). After I done all three channels, I combine them to an RGB. If it is then clear that, for example, some areas are too green, I modify the final stretch of that channel and past in the modified version of the channel). I may have to do that a few times before I get something rather well balanced to work on.

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On 2017-04-20 at 23:05, wimvb said:

Great image, Göran. Even the second version :D I like the tight stars and crisp detail in that version. You are right, it makes v1 look blurry.

This image is also extremely free from noise. Due to the abundance of data?

Wim,

thanks again and what happened to your go at the little dumbbell's big brother?

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First version is in an album I created here a few days ago. I'm struggling with Ha integration. Normally I don't do HaRGB, so I'm learning. Will come in handy once I get a new camera, hopefully the ASI1600 mono.

 

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