Adapter for mounting astro cam onto photography lens?

Is there an adapter for mounting an Astro cam onto a photography lens?  I am currently imaging on a Sony A7iii (mirrorless DSLR) with a Sigma 150-600mm (its the canon ef mount) lens.  I am wondering if there is an adapter I can use to connect an astro cam to the Sigma 150-600.  This step would be able to allow me to slowly get into an astro cam without having to get a telescope as well.  

Or should I keep my DSLR setup and get a pole master first?

Any thoughts?