The Issue of the Fajr Angle
The majority of classical and contemporary scholars consider the commencement of Fajr to corellate with 18° with fewer others holding 15° as the start of Fajr (Fatawa Uthmaani p.390 v.1 & Nawadirul Fiqh p.218 v.1). In high latitude countries of 48° and above, however, some observational data point to 14.5 - 15.5° as the onset of True Dawn. The mushahada carried out by Maulana Yakub Miftahi from ‘Hizbul-Ulama’ as well as the research carried out by Dr Asim Yusuf seem to correlate to 15 degrees which has been the secondary classical position as noted earlier.
As a preferable and precautionary act, therefore, one should initiate the fast at the earlier 18°while reading the Fajr prayer at the 15°time. This has also been the practice in Darul Uloom Karachi due to the difference between the two positions. However, if this is difficult, then one can solely act upon the 15°timetable or on the observation by Maulana Yakub Miftahi. This also correlates with the advice given by Mufti Mohammed Tosir Miah from DarulIftaBirmingham.co.uk, as well as Mufti Amjad Muhammad from Wifaqul Ulama.
In light of the above, Prayer Times Online will display both times with an emphasis on 18 degrees. The 15 degree Fajr time will be displayed at the bottom right corner.
Only Allah Knows Best