Can you mount a dish on a chimney? Yes.
Is it a good idea? No

There are some chimneys that can take it... for a while.... but a masonry chimney really shouldn't have a dish on it. Mortar is sand and portland cement mixed with water. It's final durability is subject to being mixed and used correctly and also subject to whatever conditions existed as it cured. So you may or may not have a chimney that could withstand the lateral pressures of having a dish mounted on it. A massive chimney obviously has more mass to act as a stabilizing component. A standard, single flue chimney.... maybe not so much.

I was in construction a long time, and an inspector for 9 years.
Can it be done? yes.
Would i do it on MY house? Not a chance.... and I have a brand new masonry chimney done by a crew that I KNOW does high quality masonry work. Why would I want to screw that up?

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