Gaussian blur erases edges

[jimh12345]

Gaussian blur, with a mask,  is a good way to eliminate noise in the background areas of an image, for example the sky.  There is a problem, though:  if the masked area includes the edges of the image, some of the image is erased (made transparent).  I'm attaching an example - it's a corner of a b&w image with some noisy sky, in which I've tried to fix with blur.

To avoid this I can  keep the blur effect away from the edges, using the mask.  But this leaves me with a border of noise around the image.  Alternatively I can restore the lost edge with the clone brush, but that's less than optimal. 

Is there an option I could be using to get Gaussian blur to behave better at the borders of the image?

[Ron P.]

Are you using a Gaussian Blur Live Filter ? If so, make sure the box in the upper left of the dialog beside, Preserve Alpha is checked.

[jimh12345]

Thanks Ron, I'll try that.  But I was just about to update my post - because I found out that AP's "Live Denoise" is a much better tool for the job. It did a great job of reducing the noise without noticeably affecting any of the actual detail - I didn't even need to mask.  And it doesn't mess up the edges.