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Pre-Observing
Follow this link for information about pre-observing activities: proposal preparation, pre-run activities, etc.

SCALES is an Adaptive-Optics-fed bench-mounted imager and integral field spectrograph installed at the Keck II left Nasmyth bent focal station inside the AO enclosure. SCALES provides Y-Ms infrared band imaging (0.006"/pixels, FOV 12.2x12.2") and integral field spectroscopy with low to moderate spectral resolution (0.020"/spatial pixel, FOV 2x2" low spectral resolution or 0.34x0.36" moderate spectral resolution).

The SCALES pocket guide is available here.

Principal Investigator:	Andy Skemer (UC Santa Cruz)
Science PI:	Steph Sallum (UC Santa Cruz)

The Keck II Adaptive Optics system is undergoing its HAKA upgrade. For 2026B, please plan that NGS operations will be limited to guide stars with Rmags < 12th mag within 30 arcsec of the science target; all fainter targets will be LGS within 60 arcsec of the science target. Hopefully in 2027A NGS will be expanded to cover guide stars with Rmags < 14th mag. Please see the AO website for more detail.

SCALES imager limits are expected to be similar to NIRC2's sensitivity limits.

SCALES Simulated IFS Sensitivity Limits: The numbers below are the Johnson vega mags that reach SNR=5 (measured in a lambda/D region over a pointsource) per spectral resolution element in 1 hour. There are 27 spectral resolution elements for the Low-Res modes, and 950 spectral resolution elements for Med-Res. For KLM and KL, multiple magnitudes that correspond to the K/L/M bandpasses covered by each of those modes are shown.

Table: Simulated IFS Sensitivity Limits

Low Res
K	K=20.8
KL	K=21.2 L=16.1
KLM	K=18.3 L=16.0 M=13.2
L	L=15.6
Ls	Ls=15.7
M	M=12.5
Medium Res
K	K=18.9
L	L=13.8
M	M=10.8

Pocket Guide page 1

Pocket Guide page 2