100) “If Earth were a ball, the Southern Cross and other Southern constellations would all be visible at the same time from every longitude on the same latitude as is the case in the North with Polaris and its surrounding constellations. Ursa Major/Minor and many others can be seen from every Northern meridian simultaneously whereas in the South, constellations like the Southern Cross cannot. This proves the Southern hemisphere is not “turned under” as in the ball-Earth model, but simply stretching further outwards away from the Northern center-point as in the flat Earth model.”

Milestone! Also, what do they mean?

I'm not fully sure what Dubay means here. I think he’s sort of imagining a ceiling of stars with a sphere below it or something?

You can't see all stars simultaneously, because they are all around us. And one side of the planet is day while the other is night. 

http://blog.daimonie.com/2015_11_01_archive.html

Incomprehension of the model.

Only the celestial south pole has to be visible at every single location in the southern hemisphere at the same time. The Southern Cross is not the celestial pole and therefore it is not visible everywhere in the south at the same time. Nobody says it should be. (see #103 for detailed explanation).

It only often serves as orientation to find the celestial pole because it is remotely close to it.

Same goes for the northern constellations. Everybody capable of LOOKING UP during the night should clearly see that not all the northern constellations are visible at the same time!

Sigma Octantis is the star closest to the southern celestial pole. It is a bit harder to see than Polaris because it's much fainter, but this one you CAN see from every point in the southern hemisphere at the same time (provided it's nighttime of course).

http://200proofsearthisnotflat.blogspot.co.uk/2016/02/debunking-dubay-100-109200.html