# The amateur astronomy photographed the sky with a fixed digital camera with an exposure time of 30 minutes.

The amateur astronomy photographed the sky with a fixed digital camera with an exposure time of 30 minutes. Among other stars, two white stars Alferatz (a Andromeda, a1 = 0h9m b = + 29 ° 11 ‘) and Navi (near Cassiopeia, a2 = 0h58m b2 = + 60 ° 48’) were included in the frame. The trail of which of these stars will be brighter in the image if their stellar magnitudes are 2.0bm and 2.47m, respectively? Confirm the answer with calculations.

The trail of a weaker star (near Cassiopeia) will be brighter, since it will be shorter by cos1 / cos2 = 1.78 times, and the amount of light coming from Cassiopeia will be 1.46 times less. This means that Cassiopeia has more energy per unit of track length.

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