Exposure time estimation

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Magnitude limits 

  • For Band 1 and Band 2 requests, the bright limit is K=4mag. The faint limit (SNR>40 in 8 hours) is K=15mag. However, those are extreme limits. We suggest science for sources with K mags between 6 and 14 mags. Targets fainter than 13 mag require IQ20 condtions. The optimal magnitude range for SNR~100 spectra is between 10 and 13.99 in the K-band. In this range (K=10-13.99 mag) the typical exposure time is greater than the overhead time (~12 minutes) and within the maximum observable time for a target (5 hours in 1 night). All the SNRs we quote are the average per resolution element. The center of each order is ~20% higher and the ends of the order are ~20% lower than the average.
  • For Band 3 requests, the magnitude limit is 11 mag, and Band 4 the magnitude limit is 9 mag.

Exposure time calculations

  • A simple applet for exposure time estimates is available here.
  • Exposure times estimates can made using the sensitivity tables here
Exposure time estimation | Gemini Observatory


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