When you started the hobby of astrophotography, you learned how to photograph distant galaxies using a telescope with a diameter of 6-inches. You found that the optimal exposure time for a galaxy known as DaziLu was about 90 seconds.

 

After a few months, you decided to splurge on a 10-inch telescope to take photos of DaziLu with better resolution. However, this new telescope collects light faster than your old one, and you don't want to oversaturate your camera.

 

4) What is the optimal exposure time for DaziLu using your new telescope?