^ 11.According to the Mahari Schwartz, it is preferable to pray vatikin, and according to Rabbi Shlomo Kluger in HaElef Lecha Shlomo 47, it is preferable to pray in a minyan. See Yabia Omer, Orach Chaim, part 1, 4:9, who hinges the law on kavanah. He maintains that if a person concentrates well, he should pray vatikin, but if he is unable to have kavanah, it is best that he prays in a minyan. Shut Pri Yitzchak 2 writes that since there are doubts as to when exactly vatikin is (as explained in halachah 6), it is preferable to pray in a minyan rather than to pray with uncertainty at vatikin. That is how we are accustomed to rule. However, since there are those who disagree, an individual who wants to pray vatikin from time to time may rely on their opinions.
Bei’ur Halachah 58:1 writes that people who are careful to pray vatikin every day in a minyan are permitted to pray individually when they do not have a minyan. In Halichot Shlomo 5:17 the explanation given is that these people have a sort of vow, both regarding praying vatikin and praying in a minyan, and therefore they may choose how they wish to practice.

^ 12.We learned in halachah 4 and in note 4 that according to the majority of poskim, as well as the rulings of the Shulchan Aruch 89:1 and the Mishnah Berurah 4, the time before netz is valid for prayer only b’dieved. Additionally, we learned in the previous note that there are those who say that even when the prayer in a minyan is conducted after netz, it is nevertheless preferable to pray at vatikin. Therefore, the result is that according to the majority of poskim, it is best to pray at vatikin individually and not before netz in a minyan. So writes the Avnei Yashfeh 14:1 and Yalkut Yosef 89:14.
However, we learned that according to the Rosh and Rabbeinu Yerucham the time for prayer l'chatchilah starts from misheyakir, and the Mishnah Berurah 89:1 writes that people who are awake on Shavuot night may pray in a minyan before netz. Additionally, Yaskil Avdi, part 5, Orach Chaim 10:4, and Or L’Tzion, part 2, 7:4 write that it is preferable to pray in a minyan before netz, for that is a case of extenuating circumstances, since he will not have another minyan after that. That is also the opinion of the Chazon Ish (brought by the Ishei Yisrael 13:6).
It seems to me that as a ruling to many it is preferable to preserve the prayer in a minyan, for prayer in a minyan is accepted and the power of communal worship is important in preserving the permanence of prayer. Only for a person who wishes out of piety to pray at vatikin, it may be preferable to pray at vatikin. However, ordinarily, it is best to pray in a minyan before netz.
All the more so in a small community, where a few of the congregants must leave early for work and they will not have another opportunity to organize a minyan after netz, this is considered to be a case of extenuating circumstances, and they must arrange the minyan to pray before netz. It is proper even for those individuals who can pray later on, to participate as well. (Although, if they want to wake up early, complete the early minyan, respond to their Kaddish and Kedushah, and then pray vatikin later individually, they are permitted to do so).

^ 13.The poskim who maintain that we calculate from amud hashachar are: Terumat HaDeshen, the Bach, and Eliyah Rabbah. This is also implied from a number of Rishonim, among them Rashi, Tosafot, Ramban, and Rashba (see HaZemanim BaHalachah 13:2). Although the Magen Avraham himself (233:3; 443:3) is uncertain as to whether the calculation is to be made from amud hashachar or from netz hachamah, nevertheless, he rules stringently (58:1) because Keriat Shema is a biblical mitzvah and therefore the calculation is given in his name.
In contrast to them, maintaining the Gra’s approach are Rabbeinu Chananel, Rasag, Rav Hai Gaon, Rambam, Talmidei Rabbeinu Yonah, and others. Acharonim who follow this approach include the Levush, Tosafot YomTov, and the Graz. It is also the opinion of the majority of poskim (see there 13:7-9). The Gra’s reason (Bei’ur HaGra 459, Shenot Eliyahu, the beginning of Masechet Berachot) is that the times of the day and the night are identical, and therefore one 24-hour period is divided into twelve hours for the day and twelve for the night. In calculating a whole year, the hours of the day and night are identical. This is only possible if the day is calculated according to the sun, for then the days and nights of the whole year are equal. This is not true if the calculation is made from amud hashachar until darkness, for then the days would be more than two hours longer than the nights.

^ 14.According to the Magen Avraham’s approach, there are those who calculate the hours of the day from amud hashachar until the emergence of three stars, and then the result is that before netz, 72 minutes are added, whereas after sunset only 18 or 13.5 minutes are added (Ma’amar Mordechai 233:3, Ben Ish Chai, Vayakhel 4; Divrei Yosef). However, their opinion is problematic, for based on their calculations, chatzot arrives before the sun reaches the middle of the sky, and therefore the final time for Keriat Shema according to the Magen Avraham comes out earlier than it actually is. Rav Tikochinsky, along with the prominent rabbis of Jerusalem, solved this problem by establishing the time after sunset as equal to the time before sunrise. If amud hashachar precedes netz by 72 minutes, then even after sunset 72 minutes are added. That way, it always comes out that the first six hours of the day end at chatzot, both according to the time of the Magen Avraham and according to the time of the Gra.
Based on this, it is easy to calculate the difference in time between the final time according to the Magen Avraham and the final time according to the Gra. First, we must calculate the time between amud hashachar and netz and divide it into six. For example, according to the calculation of the days of Nisan and Tishrei, when amud hashachar is 72 minutes earlier than netz, every hour according to the Magen Avraham is longer by twelve minutes. If so, the difference in time between them after three hours is reduced by 36 minutes. This means, that the final time to recite Shema according to the Magen Avraham is 36 minutes earlier than the time of the Gra, and the final time to pray the Amidah according to the Magen Avraham, is 24 minutes earlier. However, based on what we learned in note 1 concerning the changes in the time of amud hashachar in the different seasons of the year, it comes out that in the height of winter, the time of Keriat Shema according to the Magen Avraham is 39 minutes earlier, and in the height of summer, it is 44 minutes earlier than the time of the Gra.
Since this is an uncertainty concerning a biblical obligation, it seems that it is correct to make the calculation according to the position of the sun at 17.5 degrees below the horizon, for at that time the first light is visible, and some poskim maintain that time as amud hashachar, as explained in note 1. Based on this, in the days of Nisan and Tishrei, amud hashachar is 78 minutes earlier than netz, and the time of Keriat Shema according to the Magen Avraham is 39 minutes earlier than that of the Gra. In the height of winter it is 42.5 minutes earlier, and in the height of summer it is 48 minutes earlier. In many calendars, the calculations are made according to the position of the sun at 19.75 degrees below the horizon, and then the time of the Magen Avraham is earlier by approximately 45 minutes in Nisan and by 56 minutes in the height of the summer. However, as I already wrote in note 1, this approach is very problematic because at that time no light is visible in the east. Additionally, some poskim calculate 90 minutes before netz and only 18 minutes after sunset, and the result is that the time of the Magen Avraham is earlier than the Gra’s time by more than an hour. Hence, as aforementioned, this opinion is very problematic.

^ 15.There are those who wish to say that the Ashkenazic custom follows the Gra, and that Sephardim practice like the Magen Avraham. Indeed, the Chida writes that where he lived the people were accustomed to follow the Magen Avraham and, in contrast, the Igrot Moshe, Orach Chaim 1:24 writes that in Lithuania they practiced like the Gra also regarding Keriat Shema. However, the Yalkut Yosef 58:3; 89:6 writes that the Sephardic minhag is not necessarily like the Magen Avraham. Additionally, in Ashkenaz, many were stringent l'chatchilah concerning Keriat Shema and practiced like the Magen Avraham (Mishnah Berurah 58:4).

^ 16.The explanation that the time of Shacharit lasts b’dieved until chatzot is brought by the Beit Yosef, and that is the opinion of the majority of poskim. However, some say that Rabbi Yehudah does not accept the Chachamim’s opinion and "after four hours" is the time of tashlumim (reciting a prayer that was missed). If so, whoever purposely did not pray during the first four hours may not pray tashlumim, in accord with the opinion of the Ra’avan, Pri Chadash, and the Gra. The Mishnah Berurah 89:6 is apprehensive about this, and therefore writes that one who intentionally did not pray during the first four hours of the day may pray until chatzot as a voluntary prayer (tefillat nedavah). (The Rashba is more stringent and writes in his responsa that after four hours one may not pray at all.)
Concerning the half hour after chatzot, see Beirur Halachah, Berachot, the beginning of chapter 4. According to the Beit Yosef and the Rama 89:1, it is forbidden to pray Shacharit in that half-hour. However, since some maintain that it is permitted to pray Shacharit at that time, if one mistakenly prayed, he does not recite tashlumim (Mishnah Berurah 89:7).

^ 17.The Shulchan Aruch rules like the Rosh and the Tur who maintain that the time of Birkot Keriat Shema only lasts for four hours. So write the Ben Ish Chai, Va’era 5 and Rav Eliyahu in his siddur. That is also the opinion of the Yalkut Yosef 58:6, as discussed at length. The Mishnah Berurah supports his words on the opinion of the Rambam and the Pri Chadash who maintain that Birkot Keriat Shema may be recited the whole day, and the opinion of the Mishkenot Yaakov 77 who says that the law concerning them is like the law regarding the Amidah, that b’dieved they can be recited until noon. The Maharil writes that this is the custom (Ashkenaz). The Bei’ur Halachah deduces that in a case in which a person did not recite them due to circumstances beyond his control, he may recite them until chatzot. Although many Ashkenazic poskim rule stringently like the Shulchan Aruch, among them the Graz and the Chayei Adam, nevertheless many Ashkenazim also rely on the Mishnah Berurah, as written in Halichot Shlomo 7:15 and Ishei Yisrael 18:7.
Yalkut Yosef 58:6 writes that concerning the matter of Birkot Keriat Shema it is permissible to practice like the Gra. Although this is a case of doubt regarding berachot and presumably it would be proper to refrain from reciting them during a time that is controversial, in accordance with the rule that states that when there is uncertainty concerning a matter of berachot, we are lenient (safek berachot l’hakel), nevertheless, since some poskim maintain that the time of Birkot Keriat Shema lasts the whole day and others say until chatzot, therefore one may at least be lenient to recite them until four hours like the Gra rules.

^ 18.According to the majority of poskim, only the recital of the first verse is a biblical obligation and therefore the Beit Yosef and the Rama section 46:9 write that it is good to say the first verse of Shema in the Korbanot passages so as to fulfill one’s obligation of Keriat Shema with its recital. The Mishnah Berurah 46:31 writes that some say the whole first paragraph must be recited, while others say the first two paragraphs (because according to the Pri Chadash both are biblical obligations). Ideally a person should recite all three paragraphs, because according to the Pri Chadash it is good to fulfill one’s obligation of remembering the Exodus during the time that one recites Keriat Shema.
However, according to the Gra, based on the Ra’ah, it is not proper to fulfill one’s obligation of reciting Keriat Shema without its blessings. Nevertheless, in this case, in order to fulfill the obligation of reciting it within Magen Avraham’s time frame, it is better to recite it earlier by itself (Bei’ur Halachah 46:9, s.v. "V’Yotzeh"). Whoever sees that the congregation is going to miss the time of Keriat Shema according to the Magen Avraham by a few minutes, Shut Binyan Olam, Orach Chaim 4, writes that he may say it earlier with its berachot and wait at "Shirah Chadashah" for the congregation, thereby meriting the recital of Keriat Shema with its berachot within the time of the Magen Avraham, as well as prayer in a minyan.
Rabbi Akiva Eiger writes that a person who is uncertain as to whether he will succeed in reciting Keriat Shema with its berachot according to the time of the Magen Avraham must recite it before then with a stipulation that if the halachah is like the Gra’s approach or if the congregation ends up reciting Keriat Shema on time, he does not intend to fulfill his obligation with that recital, and will instead fulfill his obligation with the Shema that he will recite together with its berachot. However, Da’at Torah and Oneg Yom Tov 3 write that a stipulation cannot be effective for a biblical commandment. Indeed, the Acharonim are in disagreement regarding this. Most poskim mention in practice the advice given by Rabbi Akiva Eiger, as written in Yalkut Yosef 58:5 and Ishei Yisrael 18:18.

^ 19.Minchat Yitzchak 3:71 writes that it is preferable to pray in a minyan at the time specified by the Gra. So writes the Avnei Yashfeh 8:12. By contrast, it is the opinion of Rabbi Shlomo Zalman Auerbach (brought by Ishei Yisrael 18, note 40) that it is preferable to pray individually at the time specified by the Magen Avraham. Likewise, regarding the Sephardic minhag, there is disagreement. Minchat Yitzchak writes there that according to Sephardim as well it is preferable to pray in a minyan, However, Rav Abba Shaul writes that Sephardim practice according to the Magen Avraham and it is preferable that they pray individually instead of in a minyan after the time of the Magen Avraham. The Yalkut Yosef 89:6 writes that whoever always practices according to the Magen Avraham and knows that he will have kavanah throughout the entire Amidah, it is preferable that he prays individually within the time of the Magen Avraham. However, if he cannot concentrate well, it is best that he prays with the congregation, for then his prayer is heard.
Chazarat HaShatz must be concluded within the first four hours of the day (Mishnah Berurah 124:7). The Or L’Tzion, part 2, 7:25 writes in a footnote that one may not start Chazarat HaShatz after four hours have passed. Bei’ur Halachah 124:2 s.v. "Sheya’avor" is uncertain regarding this, for perhaps since the time of prayer lasts b’dieved until chatzot, it is possible to recite Chazarat HaShatz even after the conclusion of four hours.

^ 20.When a person prays earlier than the congregation because the minyan is late, some say he should pray outside the synagogue, and others say that because they are not practicing in accordance with halachah, he is permitted to pray earlier in their presence. See Mishnah Berurah 90:35. It seems that if by his praying earlier in front of the congregation, the people will learn from him and pray earlier too, it is best that he prays in front of them, However, if they will not learn from his example, it is preferable that he prays individually elsewhere.