It's an eBay link:
I don't think I have resolved a good reason for this.
Thank you,
Nate
No adjustable tripods back in the day so you need a scope for tall guys and a scope for short guys.
The listing says:
Mining transits were developed for use in mines or places where the user?ÿ would need to shoot a line where the plate would be in the way.?ÿ The?ÿ scope could be mounted on either the top over the main scope, or on the?ÿ outboard side.?ÿ The counterweight is also present.?ÿ ?ÿ?ÿ?ÿ
"Mining transits were developed for use in mines or places where the user?ÿ would need to shoot a line where the plate would be in the way.?ÿ The?ÿ scope could be mounted on either the top over the main scope, or on the?ÿ outboard side."
I think I am starting to get that...
The auxiliary telescope is usually offset one-half the horizontal circle diameter.?ÿ When offset to the side it can be used to sight very steep vertical angles that would not otherwise be able to sight with the main scope, e.g. 60?ø?ñ. Its line of sight is parallel with the main scope. When it is mounted above the main scope the same is true.?ÿ The main scope has to be able to transit.
