Telescope optics in surveying — identify the correct statements about image formation and reference lines in common survey telescopes. Choose the most comprehensive option.

Introduction / Context:
Survey telescopes (astronomical and Galileo types) differ in eyepiece construction and image formation. Understanding where the real image forms and how the line of sight and line of collimation are defined is foundational for precise sighting, focusing, and collimation adjustments in field instruments.

Given Data / Assumptions:

• Astronomical telescope: convex eyepiece; real inverted image at the focal plane.
• Galileo telescope: concave eyepiece; erect image with no real intermediate focus.
• Cross-hairs are on a diaphragm at the focal plane for sighting.

Concept / Approach:
In the astronomical type, the objective forms a real image at its focal plane, which the eyepiece magnifies. In the Galileo type, the eyepiece intercepts the converging beam before a real image forms, yielding an erect image. The line of sight is the ideal line through the optical centers; the practical sighting reference through the cross-hair intersection defines the line of collimation.

Step-by-Step Solution:

Verification / Alternative check:
Standard surveying texts on optics and instrument adjustment present exactly these definitions and distinctions.

Why Other Options Are Wrong:
Any single-statement choice omits other true facts; only “All of the above” covers all correct descriptions.

Common Pitfalls:
Confusing “line of sight” with “line of collimation”; in practice, collimation error is the misalignment between these ideal lines.

Final Answer:
All of the above