It depends you should get the monthly schedule for Ramadan. If u don't have u can get one on their website or at the masjid.
Here's the masjids salah timing sheet, which goes w 15degrees for Fajr: http://masjidmadeena.com/salaattimings.php If you want to stop at 18degrees, it's around 30 mins earlier. You can also install the Athan Islamicfinder app and configure it for Bellevue, with your desired calculation method.
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