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Preparing the Schneider Observatory

 

Over the summer of 2015, Dr. Nathan De Lee and three undergraduate research students: Johnathan Wilson, Shandon Stamper, and Neil Russel worked on calibrating the 11-inch telescope in preparation for the opening of the NKU Schneider Observatory. This project, funded by a UR-STEM grant, used a SBIG ST-7e CCD camera attached to an 11-inch Celestron NexStar GPS telescope to take images of both M57 (the Ring Nebula) and M71. The primary goals of this project were to quantify the depth to which we can get good signal-to-noise (S/N) on our stellar targets and to see how well the 11-inch telescope could track an object over the course of the night. The analysis led by Mr. Wilson found that we could get S/N of 100 on our stellar targets down to 15th magnitude (this about 4,000 times dimmer than the human eye can see at a dark location) in 80 second exposures. We quickly found, however, that we could not do longer exposures than approximately 80 seconds due to the tracking ability of the telescope.

Stars in M71
Figure 1: Images of stars in M71 as a function of exposure time. The stars are round, which means there is no significant distortion for 10 second exposure. At 80 seconds, the stars become clearly elongated due to limitations of the telescope tracking.

 

Mr. Stamper led the analysis of the telescope tracking. The 11-inch telescope use a computer driven drive to track stars as they rise and set in the sky. As can be seen in Figure 1, when the exposure lengths get longer the telescope starts to fall behind the motion of the stars on the sky. This causes the stars to become elongated. Beyond 80 seconds, the elongation is significant enough that it becomes hard to separate nearby stars. For projects that require minimal distortions, even short exposures will be necessary. Now that the 11-inch telescope is installed at the NKU Schneider Observatory, we will continue work on improving the tracking of the telescope. There are several routes we can use including using a guide star, stacking images, and choosing stars away from the meridian. An example of combining several short exposures of the Ring Nebula shown in Figure 2. Both analyses were presented at the Heather Bullen Summer Research Celebration, and we are in the process of purchasing a new camera for the 11-inch telescope.

Ring Nebula
Figure 2: An image of the Ring Nebula generated by stacking six 10 second exposures together.