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JimS

Orion Nebula

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After finally getting my CGEM working again and a lovely clear night last night, I decided to get back to trying to image.

I had a go at Orion Nebula to test out the gear and get myself back into swing of things.

Used Canon 450D with my 8" SCT, and manually guided using a piggyback 80mm refractor and webcam. Focused the Canon using a bahtinov mask. Took 7 exposures for 30 seconds at ISO400.

Stacked using Deep Sky Stacker and tweaked levels and curves using photoshop.

Orion Nebula - 210215 #2 small.tif

I'm happy with this first effort but I am aware that a lot of practise will be needed with all aspects of the process, as well as far more exposure time and getting my camera settings correct.

Any feedback gratefully accepted!

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Very nice image for such a small number of stacked frames and manually guided on an SCT as well....!!!

You will see a big improvement by adding flat frames to remove the vignetting, dark frames to counter thermal noise and defective pixels plus bias frames to remove read noise.

Seems like quite a lot of hassle at times but it makes such a huge difference to the final result and at least you don't need to be guiding while taking them.

I had a quick go at your image in PixInsight to remove the vignetting (as much as possible) and a little bit of noise reduction then adjusted the colour balance away from the blue cast using levels adjustment in Photoshop.

William.

 

Edited by Oddsocks
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Cheers William.

That's a massive improvement over my efforts, wow! Did you change the levels / curves at all? I'm trying to read up as much as possible about processing images, are there any resources you would recommend?

Not sure if you saw my thread about Canon LiveView but I have a massive blue tint on my Jupiter effort as well as apparently this image. Obviously more noticeable on Jupiter. Both sets were with camera at prime focus with no filters. Any ideas what might be causing the blue bias in the images?

I'm definitely aware i'll have to start adding darks, flats etc., this effort was more about testing my rig out after a long hiatus but thanks for your advice.

Jim

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No curves Jim, just levels in Photoshop.

Use the histogram tool to display the image RGB channels and adjust the levels individually by selecting the channel to work on in the drop down box and adjusting the mid point slider until all three colour channels histograms show approximately the same width then use the left slider if necessary to ensure all three channels have the same start point relative to the left hand side. Don't move the far right slider, just the mid point and left side slider in the levels tool. You will need to alternate between the left and mid point sliders several times before the colour balance is about right.

When all the histogram peaks look roughly the same then select RGB in the drop down window to work on all three channels combined and adjust the image to show the faintest parts possible without showing the background noise, only adjust the left and mid point adjusters never the right, the core of the nebula will be totally burnt out but the faint stuff should be clearly visible

Save the image with a new name, e.g., Nebula.

Now adjust the level sliders again but this time adjust for the maximum detail in the core and ignore the faint outer stuff and save the image with a new name, e.g, Core.

The next part is to difficult to try and explain by text and if you search on Google for videos on how to blend together montage images using Photoshop layers there are quite a few to choose from, basically you take the Core image as a background and the Nebula image as the foreground, overlay one above the other and wipe away and blend the overblown core from the top Nebula image to reveal the detailed core from the image below and then merge the two together using the flatten layers command.

You then end up with the final image showing detail in the core and the outer fainter areas, you would never be able to achieve that as easily with curves.

As you are not using any filters on your camera the images should if anything be biased towards red, especially from light polluted areas, so I would guess the white balance on the camera is not set up correctly, I don't know the Canon DSLR myself as I am a Nikon user but somewhere in the camera set up you should find either an option to set up a custom white point balance or a choice of colour temperatures, you will probably find that the camera is currently set for something like "Tungsten" when using it for long time exposures without a lens which would make the image too blue when using it for outdoor astro work, just have a search in the camera manual for white point settings to point you in the right place.

A few images below to show the different steps in processing your image, but note it was processed to remove the strong vignetting and noise in PixInsight before importing to Photoshop for finishing..

William.

Image at first import to Photoshop, too blue, adjust blue channel only to reduce blue, then adjust red channel only to boost red.

 

Now adjust RGB combined to show maximum detail in outer nebula without going to far to show background noise, save the image with a new name "Nebula"

 

Now adjust the levels again to show maximum detail in the core and save the image with a new name "Core"

 

Combine and blend the two images in an adjustment layer, search for online videos for "how to blend photo montages in Photoshop using layers" you will find quite a few!

 

Edited by Oddsocks
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Canon 450 White balance setting.

Here you go Jim,

Page 90 of the 450D manual, press the <WB> white balance button on the back of the camera, the current WB setting will be displayed, should be auto normally but it might currently be set to something else.

For astrophotography try setting it to either Sun or Cloudy but not Tungsten (lamp) or Fluorescent as these will give either a blue or green cast to the image.

Without filters your astro images should have a strong red cast when using the camera in a built up area which you then remove in Photoshop (or fit a LP filter to the camera).

William.

 

Edited by Oddsocks
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Thank you so much!

I will sit down and read both post properly and digest when I get home.

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Right.

Had another go with my stacked file and followed Oddsocks immensely helpful tutorial and here is what I managed to come up with.

post-24097-0-66245600-1424818124_thumb.j

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