The new moon was not seen anywhere near Jerusalem on march 15th as it was very cloudy the new moon was march 16th 2021
I would like to say that having multiple sources for new moon observation is a good idea, I just read this from 2014
While presenting himself as Karaite, Nehemiah departs from the rules on sighting the new moon. He does not sight the new moon solely in Jerusalem as the temple system requires, but accepts sightings across the Middle East in an apparent attempt to harmonize the visible new moon sightings with the Rabbinic Calendar.
On Monday April 4, 2011 Nehemiah published a report of a new moon being sighted by him from Egypt and then another report by Magdi Shamuel from Ashdod. Persons in the Israeli New Moon Society determined these reports were not valid, as indeed they were not; not being made in the vicinity of Jerusalem and for other reasons.
Nehemiah routinely reports sightings and declares the sanctification of months; based on sightings far from Jerusalem. Such sightings are invalid!
Even this year  he has wrongly declared the new year a day early based on telescopic sightings far from Jerusalem. When I asked about this, Dev replied that signal fires were used to report the sightings to the Sanhedrin. Of course this is utterly false, as the witnesses were required to report personally to the Sanhedrin to be questioned.
It was after the witnesses had been questioned in person by the Sanhedrin that the Month was declared by that court; and only then were the signal fires lit [fires were lit from hill to hill across the land] to signal the decision of the Sanhedrin!
Obviously scholars like Nehemiah and his wife Dev would have known this, so why try to deceive me? Obviously they have some agenda in trying to reconcile the sightings with the Rabbinic Calendar.
Because they ignore the rule of sighting at Jerusalem alone, and because they have approved telescopic sightings as genuine; Nehemiah Gordon and his observers lack any credibility as genuine observers of the first visible light of the new moon.