Flickering stars but from a flat image

[Octavia_]

Hello, 

Does anyone now how to do flickering stars on a flat image, I have done flickering stars a long time ago, i believe it was with the Fractal Noise but I can't remember if the image was flat or if I had done it the way I'm trying to know.

I've masked circles over each star and wanted to make it so they would just glow slightly one by one in a random order but fractal noise doesn't seem to be doing anything. 

Any ideas? 

[Rick Gerard]

Try adding Fractal noise to a new layer on top of your other layers, animate evolution so you get gray and white blotches moving around, then add Set Matte and use the Sky with Masks (holes) as the source so only the holes show through. They should now be changing shade. Next, add some Gaussian Blur to soften the edges, then add some Glow as a final step. 

That would be one of about a dozen workflows you could play with to get your stars to glow in a random order.

[Octavia_]

Thank youu for your response, I will be trying this aswell, I'm quite newish to AE so the more techniques i can try and learn i think will help me a lot in the future. I will give this a try now 🙂 

[Octavia_]

oh actually I think i did half do that, the stars are on the background layer, I made a new solid white layer and masked circles over where the stars are, is this what you mean? 

Sorry what do you mean by animate evolution? is that the evolution under fractal noise? or the "evolution options" 

These are my laters, the stars are on the background bottom layer then I created a new solid and put the masks on:

[Mylenium]

If you extract the stars e.g. with a simple Shift Channels effect based on luminance and clipped back with Levels, you are pretty much free to do whatever you want.In such a case you wouldn't even use a matte as Rick suggested, but rather just apply the noise with a blending mode. Also simply consider adding a very fine Turbulent Noise and blur it. Ultimately the "flicker" is just atmospheric turbulence and the perceived changes in brightness are not that big. A smeared up star dot fed into the Glow effect will affect the glow threshold and almost automatically give the effect.

Mylenium

[Octavia_]

Thank you for your response, I should have mentioned I'm really quite new to AE, well, I've used it along time ago and learnt different techniques but I'm not really knowledgeable on the a lot of the words so I'm not really sure what "Shift Channels effect based on luminance and clipped back with Levels " means, I Can see the Shift channels effect, I duplicated the background, wasn't sure if I was meant to mask out the sections with the stars but I tried that, I can see the luminance in the drop down menus but I'm not sure what its doing other than changing the colour, I presume it may be because I didn't do the last section "clipped back with levels" this I'm not sure what that means. This is what I was trying:

[Octavia_]

I managed to find one way that worked for me 
I duplicated the background layer, added the "Curves" effect and lowered the curve so the window was black and you could only see the stars ( i had to use the background where i masked a square around the window as the curve wasn't blackening the moon)  set the mode to: Screen and track mat luma 
added a solid black layer with Turbulent Noise, changed some of the settings and it made the stars randomly glow

i then added and a glow to the other layer just to make them brighter.

Thank you for all the replies, I appreciate the time, I'm going to try and learn as many techniques as I can as I'm looking to working with AE quite a bit. 

[Octavia_]

forgot to add i added "+time*2000" at the end of the evolution code "effect("Turbulent Noise")(21)+time*2000"