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Photometric Tool


 

This free tool is courtesy of the Madawaska Highlands Observatory. Please visit our site to explore our facility. Thank you for visiting us.

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 Madawaska Highlands Observatory 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 21.90 mag/arcsec² to more accurately reflect the local sky conditions at 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.

 
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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