f = focal length

Where is the projected image if the object is at f?

Based on the diagrams, where do you want to put the eyepiece with respect to the small image of the sum which the primary mirror produces, in order to get a nice big image of the sun projected onto a piece of paper? Do you want the eyepiece > 2f away from the primary mirror's focal plane, between 2f and 1f, or ≤ 1f?

Try drawing diagrams like this for a concave mirror.

What is the relationship between the distance to the object and the distance to the image?