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M42 Orion Nebula and Running Man

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This is my 2nd attempt at this object. Only able to use the first 4 subs as the focus slipped, so only 20 minutes of capture.

4 x 5mins 800 ISO Modified Canon EOS 450D + CLS clip filter

+ 20 x 30 sec 200 ISO for trapezium

Darks flats and bias applied to both

WO Megrez doublet 72 APO

Guided with PHD

Processed with DSS and Photoshop CS3

Back garden early hours of 15.12.10 minus 4 degrees (luckily inside a POD)

Location, Bromley Kent (light polluted suburbs of London)


Edited by carastro
  • Like 1

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That's a lovely capture, I really enjoy looking at shots of this target. Last time I tried I washed the trapezium out, think I'll give your approach a try with shorter exposures for the core. Thanks for sharing.

Sent from my iPhone using Tapatalk

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Great job looks really nice. I bet you can get a lot more out of that image than you have in Photoshop I found a great tutorial on photo shop and astrophotography that might give you some more info.

I have been trying lots of shots of the Orion Nebula but because my shoddy shutter release wont work have not been able to get a long enough exposure for more detail in the dust lanes. Here are the links to the photo shop tutorial I have found most useful they may give you some new methods when working on the image data.

Heres my attempt at the Orion Nebula and the links to the photoshop tutorial.:)


Atalas Astronomy


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Heres your image put through photoshop again using levels curves and layer masks the tutorials showed me how to do a lot more with my data hope you dont mind me having a crack at it again for you:)5275514234_c14597e8fc_z.jpg

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Thanks Ivan,

and Quatermass (love the name BTW), a number of people on other forums have had a go at re-processing this image but yours is the best one so far. The others tried to reduce the brightness of the core or the background sky but lost some of the nebula while they were at it. This one achieves both, however I can't lay claim to the re-process.

I tried to open the link but the PC was asking me which programme created it and I didn't know, so haven't managed to open the link. I do have a DVD of Adam Block called Making Every Pixel count, and am slowly ploughing my way through it.


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Glad you liked it the link is possibly asking for the adobe reader as this link

is to a pdf file.

Heres the text in case you cant open it..


Anjal C. Sharma, Ph.D.

So you spent several hours out in the cold, hunched over your polar aligned telescope,

fiddling with your astronomical camera and captured long exposures of your favorite deepsky

objects. You’ve aligned, registered and stacked the multiple minutes long exposures using a

program like Registax to smooth out the noise and are thrilled to see a single low noise and well

exposed image on your computer screen. You sit back knowing that you’ve sweated blood to

obtain these images, and are justifiably proud of the result. However, somewhere deep in the

dark recess of your mind is a lurking suspicion that maybe, just maybe, all is not well. Maybe

just maybe, you should try to improve the images a bit so that your other astronomically inclined

buddies are zapped out of their seats when they see the images.

Well, fear not. Photoshop will come to the rescue!! Adobe Photoshop in its myriad of

versions from Photoshop 3.0 to the newest Photoshop CS3 is a powerful image enhancement

program with a multitude of functionality to help you tweak your hard earned astropix to

perfection. This tutorial is a compilation of some of the methods that I’ve learned over the years

to enhance astrophotos for viewing on the computer screen or for sharing over the internet and

for printing on your home color printer. I have an older version of Photoshop (Photoshop 5.0

Limited Edition) which is just fine for performing certain basic enhancement processes such as

levels and curves adjustment, gradient mask preparation and gradient removal, color blur and

tone adjustment and sharpening of the image.

1. The Photoshop main screen and opening your image

Double click on the Photoshop icon on your desktop to open up the main screen of the program.

It will look similar to this screenshot. Then click on file, scroll down and click on open. A dialog box pops up which will allow you to

select the image that you want to open as shown below.

Select the image name and click open and the desired image will be displayed.

2. Levels Adjustment

As shown, the image is overwhelmed by skyfog resulting in the bright and light red brown

look of the sky background. Although both the flame and the horsehead nebulae are clearly visible, removal of the skyglow to obtain a darker sky background would make the nebulae

stand out significantly. In addition, although difficult to see, the image has a greater contribution

from red due to the spectrum enhanced nature of my modified Digital Rebel resulting in greater

red response of the sensor. Therefore this problem has to be addressed also. The easiest way

to do this is to use the levels function in Photoshop. Click on Image, then click on adjust and

then choose levels and the histogram information for the image pops up as shown below.

In the histogram dialog box, click on the Channel (RGB) tab, and choose Red and only the

histogram for the Red channel pops up. Now, see the small slider triangles beneath the histogram for the red channel? They define the

black (black triangle), mid-grey (grey triangle) and white (white triangle) levels within the red

histogram. We will define a new black point for the red channel by clicking on the black triangle

and sliding it to the right, until it is below where the histogram just begins to shoot up as below.

Repeat the above steps for the Green and the Blue channels and when that is done click OK on

the levels dialog box. Your result should look something like this. Compare this image to what we started out with. Dramatic improvement, isn’t it? Not only are

the nebulae significantly more visible, the faint outer extensions of the nebulosity can be seen all

over the frame, and the details in the nebulosity really stand out. In addition, most importantly,

you’ve gotten rid of that pesky skyfog problem, and the sky looks closer to what it should. You

can stop at this stage if you wish because you’ve improved the image by 90%. However,

wouldn’t it be nice to get that additional 10% too? Well, if that strikes your fancy, read on….

3. Gradient Removal Via the Layer Mask Technique

One of the issues that always faces an astrophotographer is an illumination gradient in

astrophotos, particularly if a larger imaging sensor is used. This is a characteristic of the

telescope optics, and how large of a fully illuminated field the optical train can provide at the

prime focus plane. My Sky 90 is no FSQ or Epsilon 200; however it is acceptable as an

astrograph using the APS-C sized Digital Rebel sensor, but the images always display an

illumination gradient going from image center to image corners. A Flat Field image taken using

a white T-shirt in the daytime or of the twilight sky can be subtracted out to remove this gradient.

Dark frames taken with the same camera of the same exposure duration at the same sensor

temperature can be used to remove hot pixels and the Amp glow. What if you haven’t done this,

or like me you’re too lazy to collect darks and flats and justify your laziness by saying “I’d much

rather spend precious imaging time collecting lights….flats and darks be darned.” Well duh,

now you’ve got a problem haven’t you? Well, fear not. We have the technology to mimic a flat

field by preparing a gradient mask using the image itself and subtract it out to get a result with

extremely (though not perfectly) even illumination across the frame.

Open up the levels adjusted image in Photoshop and click on Layers and then choose

Duplicate layer. The original image will be duplicated and placed right on top of the original

image as a separate layer. Check out the layers tab on the right hand side of the main screen

and you’ll see the two layers displayed. From the tools palette on the left of the image, click on the icon which looks like a rubber stamp.

This is the clone tool and it allows you to clone any area within the image on any other area.

Position this tool over an area of the image which is dark, and does not have any bright stars,

and press Alt and click together, to define that area as the clone result area. Now start cloning

out the bright stars and the extended nebulosity in the image.

Take your time, and be thorough as this step will define the first step to prepare a good gradient

mask. When you are finished, the result should look something like this. As can be seen there are still moderately bright stars in the image. You’ve only changed the

upper layer, not the original image which lies below this layer. We want a “map” of the

illumination gradient across the frame, so now click on Filter, then click on Blur and choose

Gaussian Blur.

Now use the slider beneath the radius window to define the blur pixel radius, such that it

completely blurs out the stars and just barely removes any blocky patches in the image. For this

image I found a blur radius of 40.0 pixels to be perfect. Click ok. This is the finished gradient mask layer, and needs to be subtracted out from the

original image. For this, go to the Layers box on the right hand side of the program window, and

click on the blending mode box which right now says normal.

Scroll to Difference and click. This subtracts the layer mask from the original image resulting in

extremely even illumination of the image with very little residual illumination gradient. Slide the

opacity slider to around 80% to ensure that the faint nebular regions can also be seen. We now have to blend the layers together to result in a single layer. For this choose Layer and

scroll down to select Flatten Image. This results in a single image layer with the two merged

layers as seen below in the Layers box.

Save this image and you now have improved the image by around 97% or so. Want to improve

it even further? Well, any changes done now will only improve the aesthetic appearance of the

image, and so many of the steps below can be adjusted according to your own preferences.

4. Aesthetic Improvements – Cropping, Color Blur, Saturation, Sharpening and Curves

The first thing you can do is crop the image to show only the parts of the frame which are of

interest. In this case, the normal dithering between the individual sub-exposures have resulted in a red line on the left hand side of the image. I’m going to crop the image to remove this

artifact completely. On the tools palette on the left of the image, click on the rectangular

marquee icon, then position the crosshairs on the bottom right corner of the image, and while

holding down the left click button, drag the crosshairs to the upper left to define the crop area as

shown above. Then click on Image and then scroll down and click on crop. This crops out the

non-selected areas, resulting in the image below.

There are several nice filter plugins available as freeware for photoshop. One of these plugins

is a series of filters called AAA Filters available for download from index.html. Download

these files and extract the 8bf plugin into the filters folder of photoshop. Now when you click on Filters, you can scroll down and click on AAA Filters and choose Color Blur. This opens up the

dialog box shown. Slide the radius to around 15, set opacity to 50 and set saturation to 25.

Click okay, and the result will be a very nice and correctly color saturated image with pleasingly

softened stars as seen below.

Clicking on Filter then on Sharpen and then on unsharp mask brings up the screen below. Set the radius to 1 pixel. Any more and you will have unnaturally sharpened stars, and you may

lose fine nebular details. Click OK. The result is a pleasingly sharpened image below.

The last thing that I like to do is a slight curves adjustment to make the nebulae stand out a bit

more without sacrificing too much fine detail. The way to do this is via a curves adjustment. At

the moment, the progression of the pixel bits from completely black to completely white is a

linear function. Clicking on Image, then on Adjust and then on Curves brings up the dialog box

shown below. Now grab the line somewhere in the middle and drag it up a little, to obtain a curved pixel

progression function. Be gentle here, otherwise the image will look completely garish and you’ll

lose a lot of faint detail in the nebular areas. The idea here is to subtly enhance the presence of

the nebulae but not overwhelm the image brightness and contrast.

Click okay and Voila, you’re done. Save the image. Want to see a before and after? Here you

go. Enjoy.

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Thanks for that Quatermass. Lots of bits and pieces in that I did not know and bits I was slightly unsure about now confirmed.



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I think your original image is just fine! Loads of detail! All I've done is a very very slight stretch and reduced the noise...some times less is more! It's a fantastic image!


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Great M42 - Really well captured. I am just getting into astrophotography and I am finding it really exciting.

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Lovely job. Still waiting for my first ahhh moment on my own efforts!

Had a play too....


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For 20 mins of capture, this is looking great to me, well done!!

@ Quatermass, great stuff

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I can't believe I managed to capture so much detail in only 20 mins of subs after some of the poor results I have had with many more subs previously. I am trying to work out what I have done differently.

There are only two things that have changed:

I found I was doing my flats wrong and recently put that right.

I had my DSLR modified in September and I think the combination of these two things must be the difference.

I thought you guys might be interested in this bit of information as for me it's just one more bit of the learning curve.

I was told that having the camera modified would improve the sensitivity, but I had not realised by how much.


Edited by carastro

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Thats a lovely image Carole, those 70 Megrez are certainly fast pulling in the nebulosity, I like the colours in your original possibly a little tweak on the black to take the skyglow down a touch but not too much as its a fine image


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Thanks every-one

those 70 Megrez are certainly fast pulling in the nebulosity

Yes I am pleaed with it, (I do have a slipping focus issue to sort, which was why I only managed 4 x 5 min subs), but it seems to be a very good scope for larger objects.


Edited by carastro

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Well I don't want to hurt anyone's feelings but I give Carole's original a clear preference. The background sky is at an excellent level and the layer masking is seamless without a colour boundary between the layers. S. Squid has done well on the noise though!

There is no point in trying to get much deeper into the Trapezium with 30 sec exposures, they are simply too long. You need a run at between 10 and 15 secs, I would say. At f5 and with CCD I used 11, 50 and 300 secs and should have done longer than 300 with hindslight. Once co registered these new shorts will layer mask in easily. Before flattening the layers, though, careful attention to colour balance is needed. This is where Carole's version scores for me. But she was starting from scratch with the layers, obviously. Harder curves have created boundaries to my eye.

It just needs another run and those extra shorts to become a really great M42, well balanced and natural. For the length of exposure the image is incredible.

BTW, the best layer masking tutorial I have come across is this one;

Compositing 2 Different Exposures via Layer Masks

There are some really crude techniques out there on the net but if there is a better way than this I have never met it. I suspect this is the method you used Carole?


Edited by ollypenrice

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Lovely capture Carole. Loads of detail and amazing colour. Tracking looks spot on.

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Many thanks Russ, that was nice to hear. If only you knew what problems I have been having with guiding lately.

Hi Olly,

Thanks for your comments, from some-one as experienced as yourself I take that as a compliment.

You asked about my technique for dealing with the trapezium. I have to confess I still have to master masking and layering (I have done it before so need to persevere), but I did do a layered method which I worked out myself.

I feather copied the area I wished to transfer from the 30 sec stack using the polygonal lasso tool. Then pasted it onto the 5min stack. Reduced the opacity so I could line up the stars. Did an adjustment to this layer to match the colour of the main image and then flattened the image. I did a little with the dodge tool to iron out any "seams" and then went on to process in the normal way.

BTW Olly I did actually do some 15 sec subs but as this is my first time trying to reduce the trapezium I was not sure what length would be best. I'll use them if I manage to get some more subs.

As lots of people have had a "go" at re-processing this. If any-one is interested in having access to the original RAW files so they could process it from scratch, I could drop them into drop box, however you'll have to do a separate download for each file and there are a lot of them.

It would be interesting to see what others might come up with.


Edited by carastro

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Terrific work Carole. Yes I like your original best of the lot (along with Squidies job). Just keep at it and don't expect to be able to get it all at once. I've found that by working at a level that I understand takes me onto areas which were previously incomprehensible!

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It's great to see these different versions.

It reminds me of something my brother said last week - "Don't you astronomers all end up taking pictures that all look the same?"

It's amazing that even with THE SAME DATA, we can have very different pictures!

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Carole, check out that Lodigruss link. It is well explained and works a treat.


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Looks great Carole - I am a total newbie at this and have so far only managed 2 images, one of them being the Orion Nebula. Yours looks fab. Interested in where you got your camera modded? I have the possibility of a spare 400D soon and I am wondering about going down that route. I don't want to attempt it myself.

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Interested in where you got your camera modded? I have the possibility of a spare 400D soon and I am wondering about going down that route. I don't want to attempt it myself.

As you rightly guessed I did not attempt to do it myself. Andy at Astronomiser does it for £200. It sounds a lot but I think it was worth every penny, especially when you consider how much everything else costs.

check out that Lodigruss link.

I will do Olly, I know this is something I need to nail properly.


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Astronomiser charges £150 for filter removal only, or £200 if you want the Baader filter fitted as well.

Yes, would love to get hold of your original files Carole (bored with having none of my own images to process these cloudy nights!)


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