The recommended detector setup for imaging is ramp=1.475 sec, gain=2.68 (low gain, high dynamic range). Ramp 1.475 sec is recommended to retain the maximum possible dynamic range and avoid saturating 2MASS stars which many PIs use for calibration purposes.
Maximum exposures per filter in typical sky conditions
- Ks: 20 sec
- H: 15 sec
- J: 60 sec
- Y: >120 sec
Dithering patterns. Approximately one minute is needed to maintain wavefront correction at any given sky location. Therefore, we recommend designing dithering catalogs in such a way that the telescope stays in each position for one minute, e.g., 3×20 sec exposures in Ks, or 4×15 sec exposures in H, before moving to another dithering position. We recommend a random 30×30 arcsec dithering pattern as a standard for (quasi-)point source objects. For extended objects, the dithering pattern can be larger, or offset sky observations can be used. The telescope allows dithers as large as 1 degree to be executed as offsets in the dithering catalog. Custom dither catalogs should be emailed to Joannah Hinz prior to the observing run.
The recommended gain setting is 0.95 (low) with ramp=4.426 sec. Dither size options are typically 5, 7 (default), 10, 15, 20, 30, 60, 120, 210″. Maximum exposure times are 300 seconds. Use an even number of exposures.
The recommended gain setting is 0.95 (low) with ramp=4.426 sec. Typical dither patterns are size/pattern: 1.8″-1.4″ ABA’B’ (recommended), 1.6″-1.2″ ABA’B’, 2.0″-1.6″ ABA’B’. Maximum exposure times are 300 seconds. A typical two hour block would consist of 300 second exposures with 24 visits.
Be advised that only certain combinations of grism and filter are supported by the MMIRS data reduction pipeline.
|Grism||Filter||Sp. Res. (R)||Wavelength (um)||Supported|