In Hil. Tefillah 3:1 the Rambam says that we can daven shacharit until hatzot. Do you posken like him, or is the Kessef Mishnah correct in saying that the Rambam meant that you can make up that davening by mincha? I'm not looking for a "heter for sleeping in", just trying to understand the parameters of tefillah.
1. Yes, one may daven Shacharit until hatzot. This is what the Mishna, the Talmud Yerushalmi and Rambam (MT Tefillah 3:1) state. According to Rambam, one must strive to daven by the end of the 4th hour, but if this did not work out, one may daven until hatzot even if the delay was deliberate. According to the Mishna and Yerushalmi the halacha is according to the Hachamim who do not distinguish between before and after the 4th hour, and it is therefore not required that one daven by 4 hours, even though it is clear that one should endeavor to daven earlier rather than later. The Keseph Mishna's initial interpretation of this halacha is mistaken, as he himself points out quoting the Rashba and as he later wrote in the Shulhan Arukh OH 89:1. One may not daven Shacharit after hatzot, as stated by the SA and stressed by Rama and Magen Avraham.
2. Rambam's opinion on the question of until when one can daven Shacharit has not been fully understood. I recently wrote about this subject (in Hebrew). Rambam's view is unique and very correct.
28 Tishrei 5775 Tuesday, 21 October 2014