Science Goals

Photometric Tool

OMI and the CFHT

Terrestrial Planet Finder

Solar System Astronomy

Galactic Astronomy

Supernovae Search

Extra-Galactic Astronomy

OMI Photometric Tool

This tool is adapted from "Astronomical Computing" Sky & Telescope, May 1998, ccdlimit.bas by Bradley E. Schaefer, and converted to Java Script by Larry Bogan. Adapted by The One Metre Initiative to fit this console, with filters changed to the u', g', r', i', z', used a more precise sigma error calculation routine, added mirror/lens transmission inputs, added total transmission output, changed the sky brightness output to mag/arcsec² and rounded results for better presentation. Also added to capability to calculate to a selected s/n ,sigma value and calculate limiting magnitude to a preset exposure. All values above the results be can changed to fit different conditions. The results are good to within 0.2 magnitudes. A default degraded sky is set 21.82 mag/arcsec² to more accurately reflect the local sky conditions the site, this can be changed or disabled. Total system transmission is the net multiplication effect of : quantum efficiency * mirror reflectivity (#filters) * lens transmission (#lenses) * filter transmission.

All performance calculations in the website are made from this tool and can be verified.

Zenith distance

Elongation to star

Zenith distance

Elongation to star

New

Cres.

Quart.

Gibb.

Full

Sun

Moon

Telescope aperture	cm	FWHM seeing disk at zenith	arcsec
Diameter of secondary mirror	cm	Latitude	degrees
Number of mirror surfaces		Relative Humidity	percent
Number of lenses in path		Temperature	°C
Pixel pitch	arcsec	Month
Read noise of CCD	electrons	Year
Number of exposures		Altitude	metres
Radius of photometry aperture	arcsec	Calculate optimum radius of photometry aperture (0.67 x FWHM seeing disk)
Exposure time	seconds	Calculate limiting magnitude based on exposure and s/n.
r'-band magnitude	magnitudes
Star's zenith angle	degrees
Color index	magnitudes

Parameter	u'	g'	r'	i'	z'	unit
Wavelength						microns
Sky brightness (Artificial)						mag/arcsec²
Quantum efficiency						percent
Filter peak transmission						percent
Width at half maximum						nm
Zero of magnitude						magnitudes
Mirror Reflectivity						percent
Lens transmission						percent
Calculate exposure to s/n*
Calculate exposure to 1 sigma*						magnitude
Select color to calculate exposure*						enable*

RESULTS

Parameter	u'	g'	r'	i'	z'	unit
Extinction Coefficients						mag/air mass
Total Extinction						magnitudes
Sky Brightness						mag/arcsec²
Star Count (photo. Aperture)						counts
Star count (sky aperture)						counts
Star magnitude						magnitudes
Signal to Noise ratio
1 sigma error (68%)						magnitudes

Total system transmission						percent
Exposure time						seconds
Radius of photometry aperture						arcsec

Atmospheric extinction

	Gas	Aerosol	Ozone
air mass

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