You can observe starting at 12 degree twilight anduntil, at most, 50 minutes before sunrise.
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Science exposures with less than 30 counts are not easily reduced with the pipeline.
For most observations at Gemini, follow the programs requested observing plan (nodding and exposure times). The requested exposure times should provide the desired snr for the worst conditions allowable by the program, and will otherwise provide even better snr for that program. If targets are brighter than K=7 mag, then double check that the exposure time will not cause persistence (aim for max of snr ~250-300).
The default Fowler number is 16 and this should be used whenever possible.
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