^ 8.The phrase used in Shabbat 21b to refer to sunset is mi-shetishka ha-ĥama. According to Behag, Rambam, and Maharam of Rothenburg, this means the beginning of shki’a (i.e., when the sun disappears below the horizon). Maharam explains that if we light when there is still sunlight visible, those who see the candles understand that they were lit in order to fulfill a mitzva, and the miracle is publicized. Ran and Rashba agree that the Gemara refers to the beginning of shki’a, but they follow the position of Rabbeinu Tam that it is referring to the "second sunset," 58.5 minutes (the time it takes to walk three and a quarter mil) after sunset. According to Rabbeinu Tam, Rosh, Terumat Ha-deshen, Tur, and SA 672:1, as well as most Aĥaronim (MB ad loc. 1 and Kaf Ha-ĥayim ad loc. 2), the Gemara refers to the end of sunset, or tzeit ha-kokhavim. That time is debated as well. The Rishonim disagree how much time separates shki’a from tzeit. The Ge’onim maintain that the time between shki’a and tzeit is slightly longer than the time it takes to walk three quarters of a mil; according to Rabbeinu Tam, though, it is the time that it takes to walk four mil, which is 72 minutes. See SA 261:2 and the commentaries there, especially BHL. (Also see Peninei Halakha: Shabbat 1:2:1 and n. 1). In practice, the standard ruling here is in accordance with the Ge’onim.
The vast majority of Aĥaronim maintain that the best time to light Ĥanuka candles is at the end of shki’a, when the stars are visible – in other words, tzeit ha-kokhavim. This is the position of Baĥ, MA, Taz, Eliya Rabba, Ĥayei Adam, Ben Ish Ĥai, and others. (The Prushim community in Jerusalem follow the Vilna Gaon, who writes in Bi’ur Ha-Gra 672:1 that one should light at sunset.) See Peninei Halakha: Prayer ch. 25 n. 3, where I point out that many consider tzeit to be about twenty minutes after shki’a. (Regarding Keri’at Shema, which is a Torah obligation, I recommend waiting thirty minutes. However, since lighting Ĥanuka candles is a rabbinic obligation, one need wait only twenty minutes from sunset. Some maintain that tzeit is about fifteen minutes after sunset.) A comparison of the positions of the Rishonim shows that twenty minutes is an intermediate position. Rambam maintains that one should light at sunset, Ran and Rashba maintain that one should light about 58 minutes after sunset, and Rabbeinu Tam maintains that one should light about 72 minutes after sunset. Accordingly, the view that one should light at tzeit, which in Israel is about twenty minutes after sunset, is the intermediate position. (If the candles remain lit until 52 minutes after tzeit, one meets the requirements of all the different positions.)
^ 9.According to those who maintain that one should light at tzeit, Ma’ariv takes precedence. According to MB 672:1 and BHL ad loc., if one prays Ma’ariv at tzeit, it is preferable to light the candles beforehand, in deference to the opinion that one should light at sunset. Furthermore, according to Rambam, one must light within half an hour after shki’a. If one waits to light until after praying Ma’ariv at tzeit, he will miss the opportunity to light at the proper time. Even those who maintain that one should light at tzeit agree that one may light a few minutes before then. Nevertheless, most Aĥaronim maintain that tzeit is the proper time to light, and thus praying Ma’ariv at tzeit takes precedence over lighting. They are not concerned about the opinion that one must light within half an hour after shki’a, since after Ma’ariv there are still people in the streets. Furthermore, as we saw in the previous note, the other opinion maintains that the ideal time to light is tzeit, not sunset (Ran, Rashba, Rabbeinu Tam, and others). We should add that many families sing Ĥanuka songs and give the children candy after lighting candles, in order to deepen their connection to the mitzva and the miracle of Ĥanuka. If their father were required to run to the synagogue immediately after lighting, it would diminish their enjoyment of the mitzva. If one always prays Ma’ariv late, there is no reason to change his practice on Ĥanuka. In fact, adhering to this practice will enable him to light precisely at tzeit (Yeshu’ot Yaakov 679:1).
^ 10.The candles must be lit "from sunset until the marketplace empties out." The Rishonim explain that this means about half an hour, and this is the ruling of SA 672:2. Otzar Ha-Ge’onim (Shabbat, Teshuvot §65) states that it means an hour or half an hour. Perhaps in different areas the Tarmodians would leave the market at different times.