Remove border in circle shape

[Smurf]

Hi. I need to remove this blue border around planet which arose from sharpen Wavelets in the other program.

I tried blending pictures like this:

Made two pictures, which I call:
1)Less_Wavelets
First picture, blurred, made without sharpening, where no border
2)More_Wavelets
Sharpened picture, with border.
 pictures, 

In Gimp I place Less_Wavelets on the bottom, and More_Wavelets at the top Layer.

- then click on upper Layer-Fuzzy Tool and make auto selection around planet
- Select-Feather: 165, that will move selection little inside, behind border which must be removed
- Layer-Transparency-Add Alpha Channel
- Select-invert
- Eraser Tool or Delete key pressing more time.

Now, the problem is, why my eraser tool/delete key passing from outside of selection to inside of selection, and deleting part what I don't want? If I am selected „invert“, that means I want to delete only from outside?

Can I somehow decrease or turn it OFF, that deletion not pass selection?

When I delete with the Eraser Tool, just close to the edge of the border, it is a slow process. But if I just click „Delete“, it can remove it fine „in circle shape“ and fast. But If I press delete many times, deletion is going inside of selection. If you understand me.
Thanks.

[Smurf]

I found that my "gradient delete" effect I got because I use feather selection, not normal selection! If I normally selected ellipse delete work and not pass border!

But then is a new problem, I can't select area under border automatically, that to be nice, except feather? 

I can create a new circle inside the border, but that circle will not be in center, and can't get exact shape because my planet is not 100% circle shape!!

Ideas?

[Tas_mania]

This was very rough but I added an alpha channel then 'select by color' clicked the black background and from the selection menu 'grow'.
I grew it by about 10px. Then 'clear'.

   

[sallyanne]

Or you could make your blue area, purplish in colour. And if you have the GMIC filter. Unpurple it.
Make sure your selection is inverted as it wont hurt the black

[Smurf]

Thank you guys.
I knew it that must exist another way similar to Fuzzy and Feather!

After I blended pictures. I tried many grows like 7-11, which gives me less noise(lines), then use the best.

At the end, I added some colors and in histogram little black shadow around to cover the transition.