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How to Merge/Fix My First M42 DSLR Attempt

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#1 ETXer

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Posted 15 February 2023 - 09:50 PM

Hello All,

 

A couple nights ago I was able to image M42 with my C8 (with a f/6.3 reducer) and a DSLR. I wasn't able to accumulate as much integration time as I'd like and I know flaws exist, but that's another story.

 

Basically I have 2 sets of images, one at 15 seconds, the other for 30. I processed each group in DSS with darks, flats and bias frames. Here's the result of the 15-second version:

 

 

52691131772_475f847fac_c.jpg

 

and the 30-second version:

 

52691921844_18ac006ac9_c.jpg

 

All I want to do is fix the center blown-out portion by merging that region of the darker version (15) to the lighter one (30). I've perused a bunch of tutorials, both written and video and it seems they all assume I already know some basic principles, namely the concept of layers, which is foreign to me or the instructions are very sketchy with no detail. I have Photoshop Elements, Corel PaintShop Pro (both 2020), and I also downloaded GIMP. I tried stumbling through PSE and PSP and I failed miserably. I need something to walk me through each step (that is, individual mouse clicks) of the process from the very beginning as if they're explaining it to their grandfather (or a 6 year-old). lol.gif  Is there anything online that can do this or point me in the right direction?

 

Apologies and thanks in advance,

 

Allan


Edited by ETXer, 15 February 2023 - 10:04 PM.

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#2 CowTipton

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Posted 15 February 2023 - 11:18 PM

One way to do it in Gimp is to load the 15-second version, then load the 30-second version on top of it as a layer.  You can then “erase” the trapezium area of the top layer but not with 100% opacity.  Also make sure it’s a soft edged brush shape so you don’t have hard separation lines.

 

You play with the opacity of the eraser to find a setting you prefer.

 

But, I would try working with the 30-second version alone first and simply reduce the highlights which may “unblow” the trap region to a large extent.  You’ll likely need to compensate by increasing exposure level though so the rest of the image doesn’t get too dark.

 

With your permission I can post an example of the highlight reduction using Lightroom on my iPad with the jpeg version you posted above.


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#3 SpaceMax

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Posted 16 February 2023 - 04:08 AM

I learned a lot of the basics from this book:
R. Scott Ireland: Photoshop Astronomy
The concepts of layers and masks are well explained including pictures where to click and what to do.
There should be YouTube videos as well showing how to use layers and blend them together. I’d be surprised if there is not a video on M42 exposure blending as tutorial.
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#4 primeshooter

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Posted 16 February 2023 - 04:46 AM

The simplest, quickest way (not technically the best but it will work here) is to put both as layers in PS one over other. In this case, put the darker exposure on top of the lighter. Add a black layer mask to the top exposure which hides it then just paint in white on the core with a soft brush. Then click the layer mask and blur it with feathering to hide any harsh edges. Done, and takes about 30 seconds or less.


Edited by primeshooter, 16 February 2023 - 04:48 AM.

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#5 ETXer

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Posted 16 February 2023 - 10:12 AM

One way to do it in Gimp is to load the 15-second version, then load the 30-second version on top of it as a layer.  You can then “erase” the trapezium area of the top layer but not with 100% opacity.  Also make sure it’s a soft edged brush shape so you don’t have hard separation lines.

 

You play with the opacity of the eraser to find a setting you prefer.

 

But, I would try working with the 30-second version alone first and simply reduce the highlights which may “unblow” the trap region to a large extent.  You’ll likely need to compensate by increasing exposure level though so the rest of the image doesn’t get too dark.

 

With your permission I can post an example of the highlight reduction using Lightroom on my iPad with the jpeg version you posted above.

Thanks Mike. Where I have trouble is the very beginning, that is transferring the images into or creating the layers. I know I'm missing something, but pretty much every video tutorial I've seen either has that step already done or simply says create/load into a layer. I just don't know how to specifically do that. Some tutorials also deal with the full version of Photoshop and I only have elements, although GIMP should possess all the features. I was tempted just to deal with the 30-second version, but I really want to learn how to do this.

 

You absolutely have my permission to modify as you'd like, thanks!

 

I learned a lot of the basics from this book:
R. Scott Ireland: Photoshop Astronomy
The concepts of layers and masks are well explained including pictures where to click and what to do.
There should be YouTube videos as well showing how to use layers and blend them together. I’d be surprised if there is not a video on M42 exposure blending as tutorial.

I found the book (and its accompanying DVD) and ordered it, thanks. Yes there are tutorials, but all the ones I've seen assume some basic knowledge which (yet) don't have. I'm still looking through!

 

The simplest, quickest way (not technically the best but it will work here) is to put both as layers in PS one over other. In this case, put the darker exposure on top of the lighter. Add a black layer mask to the top exposure which hides it then just paint in white on the core with a soft brush. Then click the layer mask and blur it with feathering to hide any harsh edges. Done, and takes about 30 seconds or less.

I think once I have the basic beginning steps (and I the specific "where-and what-to-click" details) figured out, I can understand that process better.

 

Thanks again everyone,

 

Allan


Edited by ETXer, 16 February 2023 - 10:13 AM.


#6 vidrazor

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Posted 16 February 2023 - 01:27 PM

Hello All,

A couple nights ago I was able to image M42 with my C8 (with a f/6.3 reducer) and a DSLR. I wasn't able to accumulate as much integration time as I'd like and I know flaws exist, but that's another story.

Basically I have 2 sets of images, one at 15 seconds, the other for 30. I processed each group in DSS with darks, flats and bias frames. Here's the result of the 15-second version:

and the 30-second version:

All I want to do is fix the center blown-out portion by merging that region of the darker version (15) to the lighter one (30). I've perused a bunch of tutorials, both written and video and it seems they all assume I already know some basic principles, namely the concept of layers, which is foreign to me or the instructions are very sketchy with no detail. I have Photoshop Elements, Corel PaintShop Pro (both 2020), and I also downloaded GIMP. I tried stumbling through PSE and PSP and I failed miserably. I need something to walk me through each step (that is, individual mouse clicks) of the process from the very beginning as if they're explaining it to their grandfather (or a 6 year-old). lol.gif  Is there anything online that can do this or point me in the right direction?

If you want to blend both images together, the simplest thing to do is align both images in any of the image editors you're using. I will explain how it's done in Photoshop (and I'll assume Elements), but the process is essentially the same for all image editors.

 

In Photoshop (and I will assume in Elements), open both images up and size and position them so you can see both on your screen. There's a few ways to drop one image on top of the other, like copy and paste, using PLACE, or as I will describe here. This important thing is to have them both centered.

 

Press and hold the shift key while you click on the background layer (on the layers tab) of the 30 second render, and drag the layer icon on to the live area (not the layers tab) of the 15 second render and release the mouse button, then the shift key. This will center the image dropped in on top of the main image below. Unless you cropped them differently, the 30 second shot should now be perfectly aligned on top of the 15 second shot, and you should see a second layer in the 15 second render in the layers tab above the background layer called Layer 1. If you click the eye icon on the left of the Layer 1 you just dropped in, it will turn it on and off you can check if they are aligned or not.

 

Assuming they are aligned, if it doesn't already have one (and it probably will), add a layer mask to the 30 second render you just dropped in on top of the 15 second render. Click on the white layer mask icon in the layers tab so you see a frame of lines around it, indicating that is the active item you will be working on, before doing that you would have seen those frames around the image icon in the layers tab indicating that was the active item. You want to make sure the layer mask is selected, as you can see in the image below.

 

Now grab a brush and set the foreground color to black, set the brush density to anywhere between 20-30% density, and start brushing away at the central blown out area of the 30 second layer, while painting in the layer mask. You should start to see the image below start to come through, and you should see a dark area start to show in the layer mask icon, as you can also see below. If you paint too much of an area away, simply change the foreground color to white and paint that area back in, then change the foreground color to black so you can continue to blend other areas back in. Just keep working back and forth until they are blended to your taste.

 

Although it may not be necessary, a better way to blend the two layers is to change the layer transform of the 30 second render you dropped in. Normally the layer transform is set to NORMAL, which is a standard opaque. If you click down arrow next to NORMAL, you see a series of options, select the option called LIGHTEN. This will replace anything that is lighter on the top (30 second) layer on to the layer(s) below it, while anything that is lighter in the lower layer will not be affected. You can see that setting below as well.

 

Finally, if your two images are NOT aligned when you dropped the 30 second layer in (by turning the top layer on and off with the eye icon to see if they are), you can temporarily turn the layer transform from NORMAL to DIFFERENCE. This will create a negative view of the top layer relative to the layer below it. Bring your screen to 100% magnification, and use the move tool to move the 30 second layer around until it snaps into alignment with the 15 second layer below it. With the move tool selected, you can use the up/down/left/right keys to move them one pixel at a time to line the layers up perfectly. When your layers are perfectly aligned, it should look near black. At 100% (or even 200%) viewing, you should be able to see when your layers are aligned. Then just turn the layer transform back to NORMAL or LIGHTEN when done.

 

And that is it.

 

Now that I've outlined all that, you should know that both your stacks can be processed to look the way you want them too in a astrophotography image processing software. I use the free open source app Siril, and in Siril you can use tools to open your dim areas up while holding back your bright areas, as well as an assortment of stacking and processing tools. I won't bother getting into that here, but know that both your stacks can be properly processed, and both stacks can even be stacked together.

 

You also have more data in your stacks than you may realized. I took your 15 second render here and separated the nebula out in Starnet, processed it separately in Photoshop using lavels and hue/sat layer tranforms with layer masks, then blended the stars back in. As you can see, you have more subtle data, and color, in your 15 second render than in areas of your 30 second render. You will be able to do better with your 16-bit renders than I can with the highly compressed 8-bit images here.

Although ultimately you want to grab more sub time, you may want to explore and experiment with an app like Siril to see what you can get from your existing stacks. wink.gif

Attached Thumbnails

  • layer process.jpg
  • m 42.jpg

Edited by vidrazor, 16 February 2023 - 02:17 PM.

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#7 ETXer

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Posted 16 February 2023 - 09:26 PM

If you want to blend both images together, the simplest thing to do is align both images in any of the image editors you're using. I will explain how it's done in Photoshop (and I'll assume Elements), but the process is essentially the same for all image editors.

 

In Photoshop (and I will assume in Elements), open both images up and size and position them so you can see both on your screen. There's a few ways to drop one image on top of the other, like copy and paste, using PLACE, or as I will describe here. This important thing is to have them both centered.

 

Press and hold the shift key while you click on the background layer (on the layers tab) of the 30 second render, and drag the layer icon on to the live area (not the layers tab) of the 15 second render and release the mouse button, then the shift key. This will center the image dropped in on top of the main image below. Unless you cropped them differently, the 30 second shot should now be perfectly aligned on top of the 15 second shot, and you should see a second layer in the 15 second render in the layers tab above the background layer called Layer 1. If you click the eye icon on the left of the Layer 1 you just dropped in, it will turn it on and off you can check if they are aligned or not.

 

Assuming they are aligned, if it doesn't already have one (and it probably will), add a layer mask to the 30 second render you just dropped in on top of the 15 second render. Click on the white layer mask icon in the layers tab so you see a frame of lines around it, indicating that is the active item you will be working on, before doing that you would have seen those frames around the image icon in the layers tab indicating that was the active item. You want to make sure the layer mask is selected, as you can see in the image below.

 

Now grab a brush and set the foreground color to black, set the brush density to anywhere between 20-30% density, and start brushing away at the central blown out area of the 30 second layer, while painting in the layer mask. You should start to see the image below start to come through, and you should see a dark area start to show in the layer mask icon, as you can also see below. If you paint too much of an area away, simply change the foreground color to white and paint that area back in, then change the foreground color to black so you can continue to blend other areas back in. Just keep working back and forth until they are blended to your taste.

 

Although it may not be necessary, a better way to blend the two layers is to change the layer transform of the 30 second render you dropped in. Normally the layer transform is set to NORMAL, which is a standard opaque. If you click down arrow next to NORMAL, you see a series of options, select the option called LIGHTEN. This will replace anything that is lighter on the top (30 second) layer on to the layer(s) below it, while anything that is lighter in the lower layer will not be affected. You can see that setting below as well.

 

Finally, if your two images are NOT aligned when you dropped the 30 second layer in (by turning the top layer on and off with the eye icon to see if they are), you can temporarily turn the layer transform from NORMAL to DIFFERENCE. This will create a negative view of the top layer relative to the layer below it. Bring your screen to 100% magnification, and use the move tool to move the 30 second layer around until it snaps into alignment with the 15 second layer below it. With the move tool selected, you can use the up/down/left/right keys to move them one pixel at a time to line the layers up perfectly. When your layers are perfectly aligned, it should look near black. At 100% (or even 200%) viewing, you should be able to see when your layers are aligned. Then just turn the layer transform back to NORMAL or LIGHTEN when done.

 

And that is it.

 

Now that I've outlined all that, you should know that both your stacks can be processed to look the way you want them too in a astrophotography image processing software. I use the free open source app Siril, and in Siril you can use tools to open your dim areas up while holding back your bright areas, as well as an assortment of stacking and processing tools. I won't bother getting into that here, but know that both your stacks can be properly processed, and both stacks can even be stacked together.

 

You also have more data in your stacks than you may realized. I took your 15 second render here and separated the nebula out in Starnet, processed it separately in Photoshop using lavels and hue/sat layer tranforms with layer masks, then blended the stars back in. As you can see, you have more subtle data, and color, in your 15 second render than in areas of your 30 second render. You will be able to do better with your 16-bit renders than I can with the highly compressed 8-bit images here.

Although ultimately you want to grab more sub time, you may want to explore and experiment with an app like Siril to see what you can get from your existing stacks. wink.gif

Thank you so much, your suggestions were very helpful! I had trouble opening the file in elements, so I actually ended up trying everything in GIMP which seems to be the closest to PS with some variations that I had to look up. But the whole "layer" concept seems to make more sense. I now know how I can apply Mike's technique as well, and with a little future experimentation try the mask technique that "Primeshooter" suggested.

 

This is my first try doing this:

 

52692987577_4557d36a47_c.jpg

 

I'll continue to tweak as necessary over the next few days to improve on it if possible.

 

Thanks again everyone!

 

Cheers, Allan


Edited by ETXer, 17 February 2023 - 06:41 PM.


#8 CowTipton

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Posted 16 February 2023 - 10:06 PM

E7-DC3221-9-A9-A-4829-AFFC-F951918-D8262

 

This is a quick pass in Lightroom on iPad just reducing highlights and increasing exposure a little to make up for it.  Of course this is on the jpeg posted here, on a raw file you should have a lot more room for adjustment and can probably make the trap area look better.


Edited by CowTipton, 16 February 2023 - 10:09 PM.

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#9 vidrazor

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Posted 16 February 2023 - 10:48 PM

Thank you so much, your suggestions were very helpful! I had trouble opening the file in elements, so I actually ended up trying everything in GIMP which seems to be the closest to PS with some variations that I had to look up. But the whole "layer" concept seems to make more sense. I now know how I can apply Mike's technique as well, and with a little future experimentation try the mask technique that "Primeshooter" suggested.

This is my first try doing this:

I'll continue to tweak as necessary over the next few days to improve on it if possible.

Thanks again everyone!

Cheers, Allan

You may want to look into the image editor Affinity Photo. It goes for a one time price of $70 (no subscription) as is very powerful and quite similar to Photoshop in capability. Like Photoshop, it has, among other features, editable layer transforms, which GIMP lacks. There's plenty of tutorials available, and it also has a series of astrophotography tools, and can even stack your data. You can download a 30-day free trial to see how you like it. If you're not going to work with Photoshop, this is the next best app to use.
 


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#10 ETXer

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Posted 17 February 2023 - 06:26 PM

E7-DC3221-9-A9-A-4829-AFFC-F951918-D8262

 

This is a quick pass in Lightroom on iPad just reducing highlights and increasing exposure a little to make up for it.  Of course this is on the jpeg posted here, on a raw file you should have a lot more room for adjustment and can probably make the trap area look better.

Thanks Mike! That's a nice result especially with only highlights and exposure adjustments. In my experience, those (along with shadows, clarity, etc.) cover most of what is required to process an image, and that was normally all I ever needed to do. It's those high-contrast scenes like this that finally forced me to expand my skill set which can at times be a frustrating process for me.

 

Cheers, Allan


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#11 ETXer

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Posted 17 February 2023 - 06:35 PM

You may want to look into the image editor Affinity Photo. It goes for a one time price of $70 (no subscription) as is very powerful and quite similar to Photoshop in capability. Like Photoshop, it has, among other features, editable layer transforms, which GIMP lacks. There's plenty of tutorials available, and it also has a series of astrophotography tools, and can even stack your data. You can download a 30-day free trial to see how you like it. If you're not going to work with Photoshop, this is the next best app to use.
 

Thanks, I'll definitely look into these. And it's nicely priced as well. I'm not against Photoshop per se, I know I wouldn't need 80% of the power it offers, plus I don't want to have to subscribe to something just to keep it working when I wouldn't be using it every day. I have considered looking for an older version, maybe something like CS5 that would still more than cover what I need. And I've seen this plugin that as far as I can tell only works with Photoshop that offers a lot of cool features. But Affinity Photo may do the same things for a lot less money and hassle.

 

Thanks again,

 

Allan



#12 Alen K

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Posted 17 February 2023 - 11:22 PM

And I've seen this plugin that as far as I can tell only works with Photoshop that offers a lot of cool features. But Affinity Photo may do the same things for a lot less money and hassle.

That’s not actually a plugin. It’s a collection of actions, which are like macros. Affinity Photo isn’t compatible with Photoshop actions. But it IS compatible with a large number of actual Photoshop plugins, both free and paid. Also, Affinity Photo product expert James Ritson has provided a large collection of astrophotography macros for Affinity Photo. 

 

https://www.jamesrit...aphy-macros.pdf

https://jamesritson....tography_macros


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#13 ETXer

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Posted 18 February 2023 - 06:34 AM

That’s not actually a plugin. It’s a collection of actions, which are like macros. Affinity Photo isn’t compatible with Photoshop actions. But it IS compatible with a large number of actual Photoshop plugins, both free and paid. Also, Affinity Photo product expert James Ritson has provided a large collection of astrophotography macros for Affinity Photo. 

 

https://www.jamesrit...aphy-macros.pdf

https://jamesritson....tography_macros

Alen, thanks this is excellent, a very comprehensive list of macros indeed; this may be the direction to go. It seems with so many options/tools available it can be almost overwhelming to make an informed decision at my early stage, but it's great to know what's out there.

 

Cheers, Allan




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