Root River Park is located south of Rochester and is owned by Olmstead County. It is a small but pretty park adjacent to the North branch of the Root river. Rochester residents don’t use this park much and that’s a shame. However, this park is beneficial to amateur astronomers. The sky is dark enough to observe faint objects on a moonless night. True, the light pollution of the city is more pronounced in the northwest, but the southern horizon is quite dark and this is the part of the sky that often interests skywatchers. In addition, the driveway to the park offers a beautiful view in all directions, and objects in the sky can be seen almost to the horizon.
During the warm months from spring to autumn, the RAC organizes public observations here on moonless nights. On Saturday 1 June it was even possible to observe with a Dobsonian telescope with an aperture of 30 inches. That night the club began measuring sky brightness for the first time, with the goal of gradually documenting light pollution.
In 2022, a light was installed on the pole including cameras. Below is a picture taken on June 1, 2024 at 11:02 pm. In the background are the stars and constellations of the late spring sky. Above the tree on the left is the trapezoid constellation of the Crow (Corvus). Above is the star Alcorab (2.94m) with the nearby star Eta Corvi (4.38m). Clockwise lower right is Gienah(2.55m), followed by Minkar (3.17m) and Kraz (2.80m). Just above the left camera is Delta Crateris (3.70m). Below the lamp turn off at the top is the star Theta Crateris (4.66m).
During the public observations in 2023 and 2024, the light was always off. However, below are images of the light-on on Wednesday, 17 July 2024, when a relatively bright waxing 12-day-old Moon was visible at the same time. The light-on represents light pollution even in this situation and even more so on moonless nights. It is then worth turning the light off for the duration of the observation, especially the digital imaging.
The club purchased light pollution measuring equipment in 2024. Below is the output of the measurements taken at Root River Park by Bob Fealey on Saturday, July 29, 2024. According to the web conversion calculator, the darkest value MPSAS 20.91 corresponds to a limiting visual magnitude NELM 6.06 mag.
Root River Park has a pretty good, low-obscured horizon. Below is an image of the western horizon on August 6, 2024 after sunset at 9:10 pm. On the left is a crescent of the 2 day 15 hour old Moon at +05° 6′ above the horizon (Az 275°27′, Alt +05°06′). The Sun at that time was already 7°42′ below the horizon (Az 301°42′, Alt -07°42′) so civil twilight had already set in, yet it was illuminating the high atmosphere. Some of the light from the Sun is shielded by clouds, which produce the so-called crepuscular rays.
Light at Root River parking on parking lot very early morning 5:56 CDT 10/1/2024
