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


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.

Broadband Imaging Figures of Merit
Filter Zeropoint
(1 ADU/s at 1 airmass)
Flux for mag=0
Sky Brightness
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)


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.

Viewing PDFs

Download Adobe Reader

To view PDF files you need Adobe Acrobat Reader. Use Adobe's online PDF conversion tools to convert to another format.