Hot zone in images

[redstamp]

This must be a well known issue, although help-a-newbie-day is hopefully soon ;-)

Took some recent shots of the moon with my Nikon D7000 - images and video.  I used a 5x barlow (I can almost hear the groans of disapproval now) as I wasn't getting the magnification I wanted from my Skywatcher 130p with my 2x or 3x, only I ran into a small lighting problem - the cone / sphere of light is blatantly obvious from the image enclosed and correcting this post-processing whilst possible would be nightmarishly time-consuming for multiple images.  I have shrunk the image, converted to JPG and increased the exposure somewhat to highlight the issue.  Also ignore the lack of focus and the abundance of dirt on the lens / CCD as it was only a test run with my new 5x barlow...

Any advice greatly appreciated (even if it includes the words "return the 5x barlow to the shop from whence it came").

Thanks.

[Leveye]

return the 5x barlow to the shop from whence it came and get a Powermate.

[redstamp]

Fair enough - but still interested why the problem occurred?

Is this a known aberration from low quality lenses or high strength barlows?

Is it because I am pushing the optical boundaries of my scope or poor alignment which may help?

And most importantly will the Powermate completely remove the problem, or just improve it slightly and why?

Sorry for the barrage of questions - just trying to learn from my mistakes...

Thanks

[toxic]

looks like the glass is not coated on both sides and getting reflection glare from the inside of the barlow tube. check if it is mat black inside barlow and focus tube.

[redstamp]

looks like the glass is not coated on both sides and getting reflection glare from the inside of the barlow tube. check if it is mat black inside barlow and focus tube.

All black but not so matt - could this be the cause then as opposed to needing a Powermate?

I just need to work out how to reduce the reflectivity then?  Would normally reach for my wire wool or emery paper, but dont want to scratch off the paint to reveal a shinier metal below - any hints on reflection reduction?