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Q: How do I observe stars or point source objects?

A: IGRINS is optimized for observing stars, and they are the simplest types of objects to observe.  Stars are placed in either position A or position B along the slit, and dithered between these two positions between exposures.  Typically we take exposures in a sequence called a "quad" where you start at position A, take one exposure, move to position B, take two exposures, and then back to position A for one final exposure, resulting in an ABBA quad.  The B positions are subtracted from the A positions such that B acts as the sky, bias, and dark subtraction for A and vice-versa.  This way all exposures get signal from your science target.  The data reduction pipeline then fits the combined of A-B frames to optimally extract the signal for your science target.

Q: How do I observe extended source objects?

A: Similar to point sources (see question above), but you must dither your object ON and OFF the slit.  A quad would look like ON-OFF-OFF-ON, similar to an ABBA quad but with ~1/√2 times the S/B since you are not getting signal during OFF exposures.  The pipeline will subtract the OFF frames from the ON frames to subtract the sky, dark, and bias.

Q: I have a star or object of magnitude X and want to get a S/N of XX.  How do I calculate my exposure times?

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