For this tutorial I will show how to use free apps to process a starless image on your phone / tablet.
This method of processing does not make the most of the data captured in the final stacked image. This is for people who want a quick "final" image, or simply dont have the time or want, to use a computer and costly software.
When post processing a stacked image, it can sometimes be very hard to process the faint nebulosity without blowing out (over exposing) the stars, especially bright ones.
The way to protect the stars is to remove them from the image and only process the actual nebulosity.
For this tutorial I will show how to use free apps to process a starless image on your phone / tablet.
There are hundreds of free apps that can edit your images on both the Google and Apple play stores. For this tutorial, I will be using Stellar Studio (Dwarf built in), SnapSeed (Android & iOS) and PhotoLayers (Andriod & iOS), both downloaded for free.
Stellar Studio is used for creating the starless image. SnapSeed is used to edit and draw out some of the data, and PhotoLayers is used to reintegrate the stars to the processed starless image.
The below assumes that you already have used Stellar Studio to create the starless image.
Processing the starless image.
1) This image is the final stacked image that has used Stellar Studio's "Auto" tab. This had performed a noise reduction and star correction. Saved as .PNG
2) This is the starless image that was produced using Stellar Studio. Saved as .PNG
3) Open SnapSeed and click the + button to add the starless image. Click "Tools" and select "Tune Image" From the list that pops up.
4) Push up from the middle of the screen and the tuning options appear. Slide your finger until "Brightness" is selected and let go.
Now slide your finger to the right and you will notice that the brightness goes up. move it to a level that you are happy with, being mindfull not to push it too far.
5) Now push up again to get the tuning options up and slide until "Shadows" is selected and let go.
This time, slide your finger to the left to darken the shadows a bit, again, being mindfull not to go too far.
6) Next up is "Highlights" This time, move your finger right to brighten the highlights a bit.
7) Now select "Contrast" and again, move your finger to the right to a nice contrast level
8) Finally, go back to "Brightness" and adjust it up if you feel it needs to be a bit brighter.
This is not an exact science, so it is always worth playing about with all of the above until you have the picture where you want it to be.
You may be thinking that the picture is either soft, or blurry. This is fine as it will sharpen up once you reintegrate it into the stared image next.
Now save the edited, starless image and close SnapSeed for the time being.
9) Now open PhotoLayers, click on "Load a Photo" and open the stacked (stared) image downloaded from Stellar Studio.
10) The picture will present on the screen. Do nothing to this picture, and certainly do NOT resize or crop it.
Just click on "Done" in the top right hand corner.
11) The picture has now been created as a layer.
Click "Add Photo" in the top middle and select the starless image that you have just saved from SnapSeed.
12) Again, do NOT rezise or crop this picture. Just click "Done" in the top right.
13) This adds the starless image as a second layer on top of the stared picture.
Click "Fit" in the bottom left.
14) The starless image has now been made the same size as the stared image underneath.
Click on the "Colour" tab in the middle at the bottom.
15) This is where the two images will start to blend.
Move the "Opacity" slider to the left. I find that putting it half way is a good starting point.
16) There are two boxes to the left side of the main image. These represent each layer. If you have imported in the order shown here, then the stared image will be bottom, with the starless above.
17) Select the stared image and click on "Colour" again.
18) This time, select "Brightness" and slide to the right to brighten the stared image.
19) Now adjust the "Contrast" slider to darken the background while preserving the nebulosity.
20) Now reselect the starless image on the left hand side and select "Colour".
21) Do a final "Brightness" and "Contrast" adjustment if you feel that it needs it. You could also adjust the "Saturation" if you wish.
22) Once you are happy with the picture then save it and show it off to the Dwarf 3 group.
