Komentarz do Rosz ha-Szana 1:5

בעליל – above the ground a great deal, where everyone can see it.

Introduction This mishnah contains a qualification of yesterday’s mishnah, regarding when the witnesses may profane Shabbat in order to travel to Jerusalem to testifythat they had seen the new moon.

שלא בעליל – below the extremity of the firmament, close to the ground. For the redness of the sun covers it and it is not recognized so well.

Whether [the new moon] was seen clearly or was not seen clearly, they profane Shabbat on account of it. Rabbi Yose says: if it was been seen clearly they do not profane Shabbat on account of it. According to the first opinion in the mishnah, witnesses can profane Shabbat in order to come to Jerusalem and testify regardless of whether the new moon was seen clearly or not. Rabbi Yose holds that if the new moon was seen clearly in a place somewhat far away from Jerusalem, then it was probably seen clearly in Jerusalem as well. In such a case witnesses would have seen it in Jerusalem and since they live close, they would not have to profane Shabbat in order to testify. Therefore those outside of Jerusalem should assume that those closer had testified and that they don’t need to come and profane Shabbat. The other sages disagree, reasoning that if you tell witnesses not to profane Shabbat when the new moon is seen clearly, they might end up not profaning Shabbat when the moon is not seen clearly, i.e. when they should profane Shabbat. Anything that might lead to witnesses not coming when their testimony is needed is discouraged.

אין מחללין – for certainly they saw it in Jerusalem. But the Halakha is not according to Rabbi Yosi.