Another basic / stupid question : Focusing Distance

[Catanonia]

I think I know the answer to this one, but need it clarifying.

I tend to get my target in frame and then focus. Now as I am becoming more adventurous my targets are smaller and hence my stars are harder to see the bahtinov mask on them even when zoom. Perhaps I should change the order.

Am i right in thinking because of the distances involved that if I, for instance, focused perfectly on Vega (big and bright), then the focusing would still be bang on as far as bahtinov is concerned with much dimmer stars.

I am guessing the focus for Vega is the same for a mag 11 due to the incredible distances involved.

Am I correct in this think ?

Thanks

Cat

[adamsp123]

Simple answer is yes, all light from these immense distances arrives as parallel lines so the focal point is the same.

I use a Bahtinov and always use a bright star for focus and then slew to my subject which is nearly always dimmer and image away without any further adjustment.

Pete