APOGEE observes the Winter Hexagon

On the frigid winter night of January 22, 2011, the APOGEE project had its first successful “observing run”. With one of the instrument-installed APOGEE fiber bundles passed through the window of the instrument assembly lab at the University of Virginia (UVa) and then coupled to a modified 10-inch Newtonian telescope just outside, APOGEE took its first spectra of other stars, as well as the planet Jupiter and the Orion Nebula.

The 10-inch telescope modification, a project of first year UVa graduate student Ben Breslauer, uses a dichroic to split optical light, sent to the Newtonian focus for acquiring and guiding objects by eye, from infrared light, sent to the prime focus where fibers in a special “mini-plugplate” receive the light to send on to the APOGEE instrument. The telescope is a scaled down version of the Sloan 2.5-m telescope, with the same f/ratio but 1/10 the diameter. With this arrangement, the 10-inch telescope sees the same diffuse background flux as expected at Apache Point and can, in principle, observe stars 5 magnitudes brighter than the 2.5-m telescope to the same signal-to-noise. But to make the acquisition and guiding easier and to ensure that fibers receive a steady stream of light, the telescope is actually used with the star images out of focus. Nevertheless, many bright and interesting astronomical objects are within easy reach of the system.

Ben Breslauer, coupling one of the 40-meter long APOGEE fiber runs from the instrument to a fiber ``harness" attached to the telescope, with 30 individual fibers plugged into a mini fiber plugplate at the prime focus of the 10-inch telescope. The fibers are arranged to span almost a 1.5 degree field of view

The goal of the 10-inch telescope project is to obtain data for assessing the APOGEE instrument performance, guiding and testing the APOGEE data reduction software pipelines, and understanding the properties of the near-infrared sky background at APOGEE’s high resolution. On the first night of observation, stars from the famous “Winter Hexagon” were observed. Interestingly, the Winter Hexagon (plus Betelgeuse, in the center of the Hexagon) provides a remarkably diverse range of spectral types useful for assessing the broad range of star temperatures that APOGEE will explore in its survey of the Milky Way. The APOGEE science team is now analyzing these important early data in a variety of ways to understand the infrared “airglow”, the spectrograph throughput, and the challenges of observing with an instrument providing such rich spectral information on stars.

A portion of the APOGEE spectra collected with the 10-inch telescope in January, showing the large diversity of spectral types in the Winter Hexagon. The top spectra, with the richest density of lines, are most representative of the expected typical APOGEE spectra (most targets will be of G, K and M spectral type). The wavelengths shown span less than 1/3 of the total APOGEE spectral region. Image by Carlos Allende-Prieto and David Nidever

The APOGEE instrument team, eagerly awaiting the first APOGEE night time spectra after their dogged and successful efforts to get the spectrograph to this point in so short a time (the APOGEE Critical Design Review was in August 2009). APOGEE instrument scientist John Wilson is in the foreground, on the right, standing next to David Nidever, who tirelessly worked to get the software reduction pipeline ready to work on the data. In the background are team members Mike Skrutskie (head of the instrument lab), Bob O'Connell, Matt Nelson, and Fred Hearty (project manager), running the instrument just outside the APOGEE assembly room


APOGEE team member Steven Majewski, guiding an exposure of Rigel in 13F, breezy weather conditions.

One thought on “APOGEE observes the Winter Hexagon

  1. Pingback: Telescope obsevation | AbcStrings

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