Is it possible to see Sydney Tower from Norah Head?

This article on sdsu.edu explains the various factors involved in how far you can see towards the horizon. Besides the straight line distance, temperature and other artefacts of the atmosphere result in refraction that may allow an observer to see beyond the straight line distance at certain times.

According to the author's javascript calculator, two objects 74km apart where the tower is 305m ASL and the car park is 14m ASL puts the tower apparently below the horizon:

Finally, we find the apparent altitude of the target: ?2.79 minutes of arc = ?0.047 degrees of arc.

However:

In your case, the dip of the sea horizon is 6.51 minutes of arc, or 0.109 degrees. These values place the target 3.72 minutes of arc, or 0.062 degrees, above the apparent sea horizon. The target is easily visible.

Reducing the target object altitude to 250m, the calculator still says that the object could be visible.

In your case, the dip of the sea horizon is 6.51 minutes of arc, or 0.109 degrees. These values place the target 1.18 minutes of arc, or 0.020 degrees, above the apparent sea horizon. The target is visible.

According to this smh.com.au article:

Our guides tell us at night you can see Norah Head lighthouse on the Central Coast.

We're standing 260 metres above Sydney

Norah head lighthouse is 28m ASL, so seems likely that if that is true, so is the original photographer's observation (or theory).

Answer: yes

It is possible and I have been doing it for a number of years . The right conditions for this only happen a few times a year , as Im from the area

No, you can not. The photo is clearly fake, and in fact their "proof" that it's real is actually proof that it's fake.

The proof shown states that the tower is based on the fact that the "target hidden height" is 288 metres, and the tower is thus visible because it's 305 meters high.

The problem with this logic is that the TOP of the tower - specifically the top of the highest antenna - is ~309 metres high - NOT the portion shown in the image. Of course, that ignores the fact the base of the tower is higher than sea level - the top of the tower is actually 327 metres above sea level.

However, if you ignore the spire, the top of the tower is around 30 metres lower - or about 295 metres above sea level.

Thus based on the calculations in the linked article, even if you were positioned 14 metres above sea level at Norah Head, at most only the very top of the tower plus the spire would be visible. Thus the photo is clearly fake.