Davening with the Neitz at Sunrise
Question
I have davened the Amidah at haneitz for almost 10 years now. I usually try to say Go-al Yisroel at the exact second of sunrise so I can start the Amidah one second after sunrise as I learned. However, I was told that there is a few minutes leniency as to it still counting as it being haneitz. One shul, in North Miami Beach, for example starts their Amidah 30 seconds after haneitz.
So, my question is, to get the zechus for davening haneitz, is there a time limit where if you exceed it, it no longer counts as davening at sunrise? I'm very OCD, so I've always tried to start the Amidah one second after the exact second of haneitz for my zipcode according to myzmanim.com. I look forward to your answer.
If I may, I have a second question. When I was at the kotel for Shavuos 3 years ago (my father's yartzeit), myzmanim.com's time for haneitz seemed to be a few minutes AFTER the other minyanim at the kotel. I didn't realize it until afterwards, but I was wondering how that is? Someone mentioned that there could be different ways to calculate the exact second of sunrise, but having it 3-5 minutes before the time I had was puzzling.
Thank you!