def read_data(filename):
    """
    Reads asteroid map and outputs a list of asteroid positions
    """
    
    data = ''
    asteroid_list = []
    i = 0
    
    f = open(filename, 'r')
    for line in f:       
        data = line.strip('\n')    
        for j in range(len(data)):
            if data[j] == '#':
                asteroid_list.append((j, i))
        i += 1
        
    f.close()   
    
    return asteroid_list