Computing Exposure Times with the IRAF Task CCDTIME
Using this form investigators can estimate the integration time,
magnitude, or signal-to-noise
ratio (SNR) for a stellar observation for a given telescope, CCD or IR imager,
and filter combination at specified seeing/airmass/sky conditions at
CTIO, SOAR, or KPNO. Simply fill in the appropriate information below
and press the Execute button.
Database files contain the telescope, filter,
and detector information necessary to compute the quantities for
CTIO, SOAR, and KPNO,
using the IRAF task ccdtime.
The Gemini Observatory maintains
calculators for its facility instruments.
CCDTIME is intended to provide an approximate exposure guide; the treatment
of sky brightness is based upon Walker (1987 NOAO Newsletter No. 10, 16); see
also discussion in Elias (NOAO Newsletter No. 37, 29).
In the form below, leave either the integration time, the magnitude, or the
signal-to-noise ratio field set to INDEF, or leave it blank,
to compute this value based on the
Rough estimates are available for the CTIO Mosaic imager using data from
the KPNO Mosaic imager. No calibration data is available yet for the
WIYN Mini-Mosaic but the calibration data for the WIYN CCD Imager
should give comparable estimates.
Investigators may select
instruments for one or both observatories using the same parameter input.
Additional information about the imaging instruments at these observatories
can be found at the Web sites for
An Excel spreadsheet for estimating DECam exposures can be found on the
CTIO DECam page.
Please use the CTIO Infrared Imager Exposure Time Calculator for CT-4m
observations with ISPI.
Information for estimating exposure times for CT-1.3m telescope can
be found on the
OSU Andicam Page.
KPNO and CTIO also maintain additional Web tools for helping
identify imaging or spectroscopic needs and exposure times. KPNO has two
tools at http://www.noao.edu/kpno/imaging/imaging.html (identify a
telescope/instrument configuration from input requirements)
and at http://www.noao.edu/kpno/spectroscopy/spect.html (predict a telescope/
spectrograph combination based on input parameters).
CTIO supports exposure time calculators for many of their optical
spectrographs - see
22 Mar 2013