Example 1 - Datasets descriptions

Acquisition keyhole imaging of two stars with dithers

This is a GNIRS acquisition keyhole imaging observation of two point sources. The observation sequence uses dither-on-target. Dithered observations nearby in time will be used for sky subtraction of each frame.

The calibrations we use for this example are:

  • BPM. The bad pixel masks are now found in the Gemini Science Archive instead of being packaged with the software. They are associated like the other calibrations. (The date in the name is the “valid from” date.)

  • Darks for the science frames

  • Flats, as a sequence of lamps-on and lamps-off exposures

Warning

The Bad Pixel Masks (BPMs) are now found in the archive rather than packaged with the software. You must get the static BPM from the archive. See Getting Bad Pixel Masks from the archive in Tips and Tricks.

Here is the breakdown of the files. They are included in a tutorial data package. They can also be downloaded from the Gemini Observatory Archive (GOA).

Science
N20120117S0014-33 (J-band, on-target)

Science darks
N20120102S0538-547 (60 sec, like Science)

Flats
N20120117S0034-41 (lamps-on)
N20120117S0042-49 (lamps-off)

BPM
bpm_20100716_gnirs_gnirsn_11_full_1amp.fits

A note about finding the darks in the GOA. Since GNIRS is not an imager and imaging through the keyhole is done only in extreme circumstances, the archive does not have calibration association rules for the darks in this case. One needs to manually search for the darks. Here is the search that was done to find the darks for this observation sequence:

  • Set a date range around the dates of the science observations. In this case we used “20120101-20120131”.

  • Set Instrument to GNIRS.

  • Set Obs.Type to DARK.

  • Set the exposure time to 60 seconds.

  • On the result table, select the darks with a “Pass” setting in the “QA” column.