IRIS2 Observing Proposals
This page contains the information necessary to prepare an observing proposal for IRIS2. This incluldes exposure time calculators for the imaging and spectroscopic modes of IRIS2 and a link to the IRIS2 Observing Manual.
Imaging
IRIS2 imaging exposure time calculator
The table below gives an indication of zero-points and limiting magnitudes for the IRIS2 broad band filters, as well as "typical" long-term average sky brightnesses. The sky brightness shortward of 2 microns has no clear seasonal variation, but can vary by up to 30% between (and especially within) nights. The K/Ks sky brightness is roughly a factor of 2 greater in summer (S) than winter (W), so the sky brightness and 5-sigma sensitivities are given separately for each.
The median optical seeing of 1.5" at the AAT corresponds to 1.2" at H-band (FWHM ~ lambda-1/5), which is what should be assumed when preparing proposals. It is worth keeping in mind however that since the commissioning of the dome air-conditioning system, up to half of all IRIS2 nights have experienced sub-arcsecond seeing.
| Filter | Zeropoint (1 ADU/s at 1 airmass) |
Flux for mag=0 (e-/s) |
Sky Brightness (mag/arcsec2) |
5-sigma limiting magnitude in 1 hr (on sky) 1.2" seeing, 2" aperture. |
|---|---|---|---|---|
| Z | 21.16 | 2.9e8 | 17.0 | 21.9 |
| J | 22.58 | 5.9e9 | 15.7 | 22.0 |
| H | 22.79 | 7.2e9 | 14.1 | 21.3 |
| Ks | 22.37 | 4.9e9 | 13.5 (W) 12.6 (S) |
20.7 (W) 20.3 (S) |
| K | 22.35 | 4.8e9 | 13.3 (W) 12.3 (S) |
20.6 (W) 20.1 (S) |
Spectroscopy
IRIS2 Spectroscopic exposure time calculator
- Exposure time estimates should assume 1.2" seeing for IRIS2 proposal purposes.
- Nodding along the slit is assumed. If the target object is nodded to blank sky, then your S/N will be a factor of sqrt(2) worse in a given exposure time than that provided.