Answer
The Passover was to be on the fourteenth day of the month (Lev. 23:5). Since Israel measured months on a lunar cycle, beginning each month with the new moon, the fourteenth of the month would always have been a full or near-full moon.
As far as the eclipse question goes, I'm no astronomer, but the point sounds correct to me. The lunar phases are observed as the moon travels around the earth (one lunar orbit takes about a month). We see only that portion of the moon that is directly facing the sun. When the moon is full, we see approximately the same portions of the moon's surface that we would see if we were standing on the sun, meaning that our perspective is very similar to the sun's. Thus, during a full moon, the moon is on the opposite side of the earth from the sun, and the earth is between the sun and the moon. This would seem to be the optimal positioning for a lunar eclipse, but an impossible positioning for a solar eclipse. During a solar eclipse, the moon must come between the earth and the sun, but this would seem to be possible only during a new moon.
Answer by Ra McLaughlin
Ra McLaughlin is Vice President of Finance and Administration at Third Millennium Ministries.