Star Mask Circular Squares - Hexagonal

[Radar]

When I am making a star mask, sometimes I get a square with rounded corners or hexagons on the star mask and not circles. Does this affect the image? If so, which setting should I adjust to ensure I get circles please?

Thank you.

Ray

[msmythers]

Ray

First as to if the shape of the stars in the star mask effect the image that answer is yes. As to how much or in what way it depends on what the image is and what you trying to do with the star mask. Now as to what is the cause of the non rounded corners that is easy. The Structure Growth settings of scales and the Smoothness parameters in the Mask Generation section.

Here is a simple screen shoot showing what happens with stars when changing these parameters. First on the left we have masks that have a Large-scale setting of 2 and different Smoothness settings of 0, 5 and 10. The second row of masks have no scale setting but we change the Smoothness from 0, 5 and then 10.

Hope this helps.


Mike 

[Radar]

Mike thanks very much for that reply. Greatly appreciated.

Regards

Ray

[Radar]

Once I get the mask with round stars (Structure Growth, Large Scale = 0 / Small Scale = 0), I enlarge the stars on the mask (not the image) with MT so that the mask stars encompass the image stars slightly (this has to be done otherwise I don't see any discernable effect on the stars), but PI still begins to make my mask stars into hexagons with MT when using dilation.

Also when I use MT with the mask to reduce the star size, it seems to just reduce the star intensity, but actual star size remains the same. Large stars simply turn gray, but don't actually reduce. Tried a million different settings already. Could you again point me in the right direction here please. Bear in mind I'm using Keller's book and video tuts in parallel to coming here. Nothing is working.

Here are some clues. I should mention that this image has plenty of small background stars, heaps of nebulosity, but about 10 big foreground stars (they are big and bulbous) that I want to shrink. I can get the mask to select just those bright ten stars, but then running MT on them with erosion with a million different settings just doesn't seem to reduce them. It either fades them to a gray or turns their cores gray, but actual star size reduction does not happen.
 
If anyone can shed some light on this problem, I'm all ears. Thanks again, in advance.

Ray

P.S There is no help file or mouse over pop out windows with morphological transformation either. 

[pfile]

read RBA's article here:

http://www.deepskycolors.com/archivo/2011/09/08/star-size-reduction-via-Morphological-.html

i've been using this method successfully for years and years

rob

[Radar]

Hi Rob,

Thanks for posting that tutorial. The tutorial you posted says that MT is used for small sized stars (8th paragraph).

This tutorial will show you one way to reduce the size of small stars.

I'm trying to reduce big bloated stars. You have confirmed what I was already thinking though, that MT is not suited to big stars like mine and some other process lurks in the PI interface somewhere. The tutorial indicates that I should be using Dynamic Range Compression for big stars.

Your equipment probably gives you stars in the range where MT can have a decent effect. My equipment gives me large stars that is beyond the morphological transformation abilities.

Either way, you posting that tutorial has given me information to solve this problem, so I really appreciate it. I was watching video tutorials and sure, it looks really simple to use MT, but I just couldn't understand why it wasn't working on my image. Its also good to know I don't have the onset of some neurological disorder 

I'll tackle DRC in the coming hours.

Regards

Ray

[pfile]

AP might in and of itself be a neurological disorder!

yeah not sure how to reduce big stars cleanly. there is a script that can reduce star halos but it is quite involved and i have only used it a couple of times. Scripts > Utilities > Star Halo Reducer. I am not sure if this script could address your problem... i think you have to run on each big star individually.

rob

[Radar]

Star Halo Reducer doesn't really do what I need. You are right, its quite involved to use as well.

Ray