Stellar Observations Network Group (SONG): SONG in New Mexico

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====October 2025====

Fiber spool 241586 (the better of the two) was pulled through the conduit.

Using fiber 2 for the science fiber, as it had consistently highest measured throughput. Absolute and relative throughputs with cal lamps were similar to those measured using the fibers in the lab.

In the focal plane, fiber 2 is the lowest, with fiber 3 above it and fiber 1 at the highest row. At the maximal separation between the different fibers, fibers 3 and 1 overlap in the redder orders. The ferrule was rotated (to about 45 degrees) to avoid this.  Without a shutter in the direct calibration feed, the direct calibration fiber was left unconnected.

First light on 251002 obtained spectra! However, images with iodine cell appeared poor and resulting spectra had much lower throughput than without iodine, perhaps due to combination of image quality and guiding on poor images.

Modifications made to change guiding to ignore saturated pixels to allow for longer exposure times to average out the seeing.

251003 observed several stars. Throughput without iodine doesn't look too bad when compared with Tenerife measurements, a little lower, but not dramatically so. Throughput with iodine still looks poor. In plot below, three dots are from SONG paper with photon rates from these three stars, claimed to be median of many exposures. Repeatability of multiple observations of multiple stars is encouraging from the point of view of guiding.

251006 repeated observations of several stars.

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