Moving the guider. Photo Credit: Ardis Maciolek
MATERIALS AND PROCEDURE
Data Collection
Two computers were used to control the telescope and spectrograph. They were
SUN workstations running UNIX. These were powerful enough to handle the amount
of information that was being transmitted between the two computers, the
instruments and the network.
The first computer controlled the telescope. Coordinates for the star were entered, along with the name and additional notes which included the magnitude. The user would then select the star to be observed from the entered list and then the telescope would sweep over to the area of the star. All information was also recorded on an observer’s log sheet.
An auto guider was used to track the star. In order to use the guider, the telescope must be pointed very close to the star. Once near the star, an intensifier was used to amplify the light. This is helpful to identify stars with dim magnitudes that push the limits of the telescope. A small video camera displays the telescope’s field of view. The guider is then ‘locked’ on the star by using a key pad which allows one to manually move the telescope with a push of a button. Once in place, the guider will track the star’s path throughout the integration.
Moving the guider. Photo
Credit: Ardis Maciolek
The spectrograph was operated by a second computer. In this computer, the user would input commands such as integration time and the nature of the object or the task. This computer also displayed the spectrum complete with the photon count.
In order to acquire data that was accurate, a photon count of around 10,000 was ideal, to ensure a solid signal-to-noise ratio. The observed stars had fairly bright magnitudes, but it was better to take a series of exposures and stack them rather than to take a single exposure. However, not all stars had the same visual magnitude. Thus, the integration times varied from 300-1800 seconds and one to five exposures were taken of each star to try to come as close to the photon count as possible.