When the distance to the Sun is measured with a sextant it's about 3,000 miles. The Sun itself is not a physical object, it's holographically projected off of the domes mirrored surface and its position is dependant in part on the observer. However to answer your question based on my understanding, the Sun stays the same distance from the dome at all times.
A few years back Japan tested the world's most powerful green LASER, they fired it at the north star Polaris and it bounced off the dome and hit Soldier Field in Chicago, IL. Using this LASER the distance to the dome could be measured with great precision. Once this has been done it would simply be a matter of subtracting the Sun's distance to get the distance between the Sun and dome. This is of course assuming the sextant is measuring the height of the projection and not just the point it reflects off the dome.
Six Solar Observatories shut down at the same time.
https://www.youtube.com/watch?v=Ys1o1d69lnQ
not only that the entire town deserted and main lab door unlocked in Sunspot New Mexico, WTF
I'm watching this curious situation closely, I've got my fingers crossed that this is the beginning of the end for the globalists...