MaxImDL / Photoshop Layering Method
This is a fairly quick and easy method to use MaxIm DL and Photoshop to layer an image so that faint detail can be enhanced without losing the color balance.
1) Create your combined image in MaxIm. This could be an RGB, LRGB, RRGB or whatever you desire.
Here's the RRGB image I started with in MaxIm. I adjusted the screen stretch so that the detail in the core was not too washed out.
2) Perform a Stretch using Linear, Screen Stretch, and 16-bit settings. This will allow this image to look just as it appears when opened in Photoshop. Save this image as a 16-bit TIFF image with a name like M27_bottom.tif. This will be your bottom layer.
3) Now drag the slider down on the histogram until your happy with the outer detail and dim stars you would like to show in your image. Here's what I ended up with. You can tune this to your taste. Notice how the core is too washed out.
4) Perform another Stretch using Linear, Screen Stretch, and 16-bit settings. Save this image as a 16-bit TIFF image with a name like M27_bottom.tif. This will be your top layer.
5) Open up both the top and bottom layer images in Photoshop.
6) Convert both images to 8-bit by selecting Image / Mode / 8 Bits/Channel.
7) Activate the top layer image which shows the outer detail. Copy the entire image by hitting Select / All, then Edit / Copy.
8) Activate the bottom layer image and paste the top layer image as a new layer by selecting Edit / Paste. You should now have an image that has the faint detail in the top layer and the core detail in the bottom layer.
9) Make sure the top layer is active on the Layer palette (shown lower right). Using the Lasso Tool, drag a selection around the core area where you would like to reveal the detail from underneath.
10) From the Select menu choose Modify / Expand and enter the number of pixels. I chose 15 for this one. Then from the Select menu choose Feather and enter the number of pixels. I chose 45. You can play around with what numbers you like for these operations. Generally the larger the area the larger the numbers should be.
11) Now select the Eraser Tool with a fairly large brush. I had about 160. You can also adjust the Opacity to control how much of the upper layer will be erased. Anywhere between 75% to 100% would be a good starting point. Just keeping undoing the operation until your happy with the setting. Insure the top layer is activated. Click on the image and drag the eraser around until all the area within and nearby the selected mask is erased. Be aware that the feather operation causes some of the pixels outside the mask to be selected for a smooth transition so make sure you erase a significant area outside the selection. Only pixels that are selected will be erased so you don't have to worry about erasing too much. ***Important***: Erase the entire area without releasing the mouse button. Otherwise you will not get a smooth erase across the entire area. This may not apply only if you set your opacity to 100%.
Here's me erasing the core area from the top layer:
12) Once your done erasing, from the menu select Layer / Flatten Image. Then save the file out to a new filename in your favorite format such as JPEG. Your final result should now show the faint outer detail while preserving the look of the core.
Here's the final Image:)
13) Hopefully this will give you some new ideas for processing your images. There are several things that can be done using some of the fundamentals described in this layering technique. For example you might be able to obtain a similar result by just bringing that bottom layer into Photoshop, performing the same feathered selection described above, then invert the selection and adjust the histogram and curves to bring out the outer detail.
Good luck with your images!