///////////////////////////////////////////////////////////////////////////

//

//	Copyright (C) 2008 Michael V. Newberry. All Rights Reserved.

//

//	This copyright notice must be included in any portion of this source

//	code that is used in any form and for any purpose.

//



var _pix = 10;			// microns

var _fl = 2700;			// mm

var _bin = 1;

var _darkcur = 0;

var _darkcurbinned = 0;	// for binned pixel

var _base = 0;

var _scale = 1;			// arcsec/pix

var _gain = 1;			// e-/ADU

var _rnoise = 0;			// e-

var _vfluxatmagzero = 0;

var _fluxatmagzero = 0;

var _skyflux = 0;			// ADU/s/pix

var _vstar = 0;

var _vsky = 0;

var _bw = 800;			// Angstroms

var _eff = 75;			// percent

var _qe = 80;			// percent

var _diam = 300;			// mm

var _diamsec = 75;		// mm

var _totalbgflux = 0;		// ADU/s/pix

var _exptime = 0;		// sec

var _bgsnr = 0;

var _seeing = 2;			// arcsec

var _aper = 3;			// pixels

var _aperxfwhm = 0;

var _objareasec2 = 0;

var _objareapix = 0;

var _aperarcsec = 0;

var _objflux = 0;			// object flux through aperture

var _snr = 0;

var _magerr = 0;

var _str;

var _aperfrac = 0;		// aperture fraction of 2D Gaussian

var _trans;				// filter transmission, percent



//////////////////////////////////////////////////////////////

function DefaultInputs( form )

{

	Camera_ST8e( form );

	Telescope_1( form );

	Observation_1( form );

}



//////////////////////////////////////////////////////////////

function DarkCurrent( form )

{

/*

	t = eval( form.TEMP.value ) + 273;

	t3 = t * t * t;

	_darkcur = 1300 * 122 * t3 * Math.exp( -6400 / t )

*/

	_pix = eval( form.PIX.value );

	_bin = eval( form.BIN.value );

	

	dref = eval( form.DREF.value );

	temp = eval( form.TEMP.value );

	tref = eval( form.TREF.value );

	tdbl = eval( form.TDBL.value );



	// dark current for unbinned pixel

	_darkcur = _pix * _pix * (dref / 16.022) * Math.exp( 0.69315 * (temp - tref) / tdbl );

	

	// dark current for binned pixel

	_darkcurbinned = _darkcur * _bin * _bin;

}



//////////////////////////////////////////////////////////////

function BaseNoise( form )

{

	dn = eval( form.EXPTIME.value ) * _darkcurbinned;



	_rnoise = eval( form.RN.value );

	rn = _rnoise * _rnoise;

	

	_gain = eval( form.GAIN.value );

	gn = (_gain * _gain - 1) / 12;

	

	_base = Math.sqrt( dn + rn + gn );

}



//////////////////////////////////////////////////////////////

function ImageScale( form )

{

	_fl = eval( form.FL.value );

	

	_scale = _pix * _bin / ( _fl / 206264.8062 ) / 1000;

}



//////////////////////////////////////////////////////////////

function VFluxAtMagZero( form )

{

	_bw = eval( form.BW.value );

	_eff = eval( form.EFF.value );

	_qe = eval( form.QE.value );

	_diam = eval( form.DIAM.value );

	_diamsec = eval( form.DIAMSEC.value );

		

	_vfluxatmagzero = 940 * _bw * (_eff / 100) * (_qe / 100) * Math.PI * (_diam * _diam - _diamsec * _diamsec) / (4 * 10 * 10);

}



//////////////////////////////////////////////////////////////

function FluxAtMagZero( form )

{

	_eff = eval( form.EFF.value );

	_qe = eval( form.QE.value );

	_diam = eval( form.DIAM.value );

	_diamsec = eval( form.DIAMSEC.value );

	_filter = form.FILTER.value;

	_trans = eval( form.TRANS.value );

	

	if ( _filter == 'Johnson V' )

		flux0 = 8.66e5;

	else if ( _filter == 'Johnson B' )

		flux0 = 3.9e5;

	else if ( _filter == 'Johnson U' )

		flux0 = 5.5e5;

	else if ( _filter == 'Cousins R' )

		flux0 = 1.1e+6;

	else if ( _filter == 'Cousins I' )

		flux0 = 6.75e5;

	else if ( _filter == 'Clear' )

		flux0 = 4.3e6;

	else

		flux0 = 0;



	_fluxatmagzero = flux0 * (_trans / 100) * (_eff / 100) * (_qe / 100) * Math.PI * (_diam * _diam - _diamsec * _diamsec) / (4 * 10 * 10);

}





//////////////////////////////////////////////////////////////

function SkyFlux( form )

{

	_vsky = eval( form.VSKY.value );

	_gain = eval( form.GAIN.value );

	

	_skyflux = ( _fluxatmagzero * Math.exp( -0.4 * Math.LN10 * _vsky ) * _scale * _scale ) / _gain;

}





//////////////////////////////////////////////////////////////

function TotalBgFlux( form )

{

	_totalbgflux = _skyflux + ( _darkcurbinned ) / _gain;

}





//////////////////////////////////////////////////////////////

function BgSnr( form )

{

	_exptime = eval( form.EXPTIME.value );

	

	_bgsnr = Math.sqrt( _totalbgflux * _exptime * _gain );

}





//////////////////////////////////////////////////////////////

function AperRadPix( form )

{

	_aper = eval( form.APER.value );

	_seeing = eval( form.SEEING.value );

	if ( _aper < 0.1 )

	{

		Message( form, "Aperture too small" );

		return;

	}

	if ( _seeing < 0.1 )

	{

		Message( form, "Seeing too small" );

		return;

	}

		

//	_aper is entered in units of FWHM (e.g., "3" means 3 times FWHM in arcsec)

//	_aperradpix = _aper * _seeing / ( 2 * _scale );

//	_objareasec2 = Math.PI * _aper * _aper * _seeing * _seeing / 4;

//	_objareapix = _objareasec2 / ( _scale * _scale );



	aperradpix = _aper;

	_aperxfwhm = 2 * _aper * _scale / _seeing;

	_objareasec2 = Math.PI * (aperradpix * _scale) * (aperradpix * _scale);

	_objareapix = _objareasec2 / ( _scale * _scale );

	_aperarcsec = 2 * _aper * _scale;

}





//////////////////////////////////////////////////////////////

// comptes object flux through aperture using circular Gaussian profile

function ObjFlux( form )

{

	_vstar = eval( form.VSTAR.value );

	

	_objflux = _aperfrac * _fluxatmagzero * Math.exp( -0.4 * Math.LN10 * _vstar ) / _gain;

}





//////////////////////////////////////////////////////////////

function Snr( form )

{

	_snr = Math.sqrt( (_objflux * _exptime * _gain)

		 / ( 1 + Math.max( 1, _objareapix ) * ( (_totalbgflux * _exptime * _gain)

		  + ((_gain * _gain - 1) / 12) + (_rnoise * _rnoise) ) / (_objflux * _exptime * _gain) ) );

}





//////////////////////////////////////////////////////////////

function MagErr( form )

{

	_magerr = 2.5 / Math.LN10 / _snr;

}





//////////////////////////////////////////////////////////////

function ToStr( num )

{

	_str = sprintf( '%.3f', num );

	return _str;

}



//////////////////////////////////////////////////////////////

function CalcAll( form )

{

	DarkCurrent( form );

	BaseNoise( form );

	ImageScale( form );

	FluxAtMagZero( form );

//	VFluxAtMagZero( form );

	SkyFlux( form );

	TotalBgFlux( form );

	BgSnr( form );

	AperRadPix( form );

	GaussFrac2dLookup( form );

	ObjFlux( form );

	Snr( form );

	MagErr( form );



	form.dark_current.value = ToStr( _darkcurbinned );

	form.base_noise.value = ToStr( _base );

	form.image_scale.value = ToStr( _scale );

	form.sky_flux.value = ToStr( _skyflux );

	form.total_bg_flux.value = ToStr( _totalbgflux );

	form.noise_ratio.value = ToStr( _skyflux / _totalbgflux );

	form.bg_snr.value = ToStr( _bgsnr );

	form.aper_x_fwhm.value = ToStr( _aperxfwhm );

	form.aper_arcsec.value = ToStr( _aperarcsec );

	form.obj_area_sec2.value = ToStr( _objareasec2 );

	form.obj_flux.value = ToStr( _objflux );

	form.snr.value = ToStr( _snr );

	form.magerr.value = ToStr( _magerr );

	form.ap_frac.value = ToStr( 100 * _aperfrac );	// convert to percent

}



////////////////////////////////////////////////////////////////////

function Message( form, msg )

{

	w = 400;

	h = 150;

	var pos = sprintf( 'left=%d,top=%d,width=%d,height=%d', window.event.screenX-w/2, window.event.screenY-h/2, w, h );

	var generator=window.open( '', 'MsgWin', pos );



	generator.document.write( '<html><head><title>SNR Calculator Message</title>' );

	generator.document.write( '<link rel="stylesheet" href="styles/mirametrics.css">' );

	generator.document.write( '</head><body>' );

	generator.document.write( '<br><p class="norm150">' );

	generator.document.write( msg );

	generator.document.write( '</p>' );

	//  generator.document.write( '<p><a href="javascript:self.close()">Close</a></p>' );

	generator.document.write( '</body></html>' );

	generator.document.close();

}



//////////////////////////////////////////////////////

function ClearResults( form )

{

	form.snr.value="";

	form.magerr.value="";

	form.dark_current.value="";

	form.base_noise.value="";

	form.image_scale.value="";

	form.sky_flux.value="";

	form.total_bg_flux.value="";

	form.noise_ratio.value="";

	form.bg_snr.value="";

	form.aper_x_fwhm.value="";

	form.aper_arcsec.value="";

	form.obj_area_sec2.value="";

	form.obj_flux.value="";

	form.ap_frac.value="";

}



//////////////////////////////////////////////////////

function ClearInputs( form )

{

	form.PIX.value="";

	form.QE.value="";

	form.RN.value="";

	form.GAIN.value="";

	form.BIN.value="";

	form.TEMP.value="";

	form.TDBL.value="";

	form.TREF.value="";

	form.DREF.value="";

	form.FL.value="";

	form.DIAM.value="";

	form.DIAMSEC.value="";

//	form.BW.value="";

	form.EFF.value="";

	form.VSTAR.value="";

	form.EXPTIME.value="";

	form.SEEING.value="";

	form.VSKY.value="";

	form.APER.value="";

	form.TRANS.value="";

//	form.FILTER.value="Clear";



}



//////////////////////////////////////////////////////

function Camera_ST8e( form )

{

	form.PIX.value=9;

	form.QE.value=70;

	form.RN.value=15;

	form.GAIN.value=2.3;

	form.BIN.value=1;

	form.TEMP.value=-15;

	form.TDBL.value=6.3;

	form.TREF.value=25;

	form.DREF.value=6;

}



//////////////////////////////////////////////////////

function Telescope_1( form )

{

	form.FL.value=3000;

	form.DIAM.value=300;

	form.DIAMSEC.value=75;

	form.EFF.value=90;

}



//////////////////////////////////////////////////////

function Observation_1( form )

{

	form.VSTAR.value=15;

	form.EXPTIME.value=60;

	form.SEEING.value=2.5;

	form.VSKY.value=20;

	form.APER.value=5;

	form.TRANS.value=100;

	form.FILTER.value = 'Johnson R';

}



////////////////////////////////////////////////////////////////////////////

function GaussFrac2dLookup( form )

{

	// integral of 2-D Gaussian function I(r/sigma) = integral[ 10 * r/sigma ]

	integral = new Array();

	

	integral[0] = 0.000000;

	integral[1] = 0.005159;

	integral[2] = 0.020478;

	integral[3] = 0.043585;

	integral[4] = 0.077596;

	integral[5] = 0.118150;

	integral[6] = 0.164268;

	integral[7] = 0.217997;

	integral[8] = 0.274646;

	integral[9] = 0.332261;

	integral[10] = 0.393318;	// 1 sigma

	integral[11] = 0.454462;

	integral[12] = 0.512948;

	integral[13] = 0.570322;

	integral[14] = 0.624838;

	integral[15] = 0.675165;

	integral[16] = 0.722630;

	integral[17] = 0.764472;

	integral[18] = 0.802221;

	integral[19] = 0.835890;

	integral[20] = 0.864689;	// 2 sigmas

	integral[21] = 0.889805;

	integral[22] = 0.911216;

	integral[23] = 0.929147;

	integral[24] = 0.943950;

	integral[25] = 0.956116;

	integral[26] = 0.965995;

	integral[27] = 0.973828;

	integral[28] = 0.980198;

	integral[29] = 0.985077;

	integral[30] = 0.988897;	// 3 sigmas

	integral[31] = 0.991824;

	integral[32] = 0.994022;

	integral[33] = 0.995690;

	integral[34] = 0.996918;

	integral[35] = 0.997812;

	integral[36] = 0.998470;

	integral[37] = 0.998938;

	integral[38] = 0.999268;

	integral[39] = 0.999503;

	integral[40] = 0.999665;

	integral[41] = 0.999776;

	integral[42] = 0.999853;

	integral[43] = 0.999904;

	integral[44] = 0.999938;

	integral[45] = 0.999960;

	integral[46] = 0.999975;

	integral[47] = 0.999984;

	integral[48] = 0.999990;

	integral[49] = 0.999994;

	integral[50] = 0.999996;

	integral[51] = 0.999998;

	integral[52] = 0.999999;

	integral[53] = 0.999999;

	integral[54] = 1.000000;

	integral[55] = 1.000000;

	integral[56] = 1.000000;

	integral[57] = 1.000000;

	integral[58] = 1.000000;

	integral[59] = 1.000000;



	sigmas = _aperxfwhm * 2.354820 / 2;	// convert diameter to sigma's

	index = sigmas * 10;

	index1 = Math.floor( index );

	

	if ( index1 < 0 )	// below 0 radius

	{

		_aperfrac = 0;

	}

	else if ( index > 59 )	// 6 sigmas or greater

	{

		_aperfrac = 1;

	}

	else

	{

		var frac = index - index1;

		_aperfrac = (1-frac) * integral[ index1 ] + frac * integral[ index1+1 ];

	}



	return _aperfrac;

}



/////////////////////////////////////////////////////////////////////////

function SaveCookie()

{

	var form = document.forms['signoise'];

	if ( form == null )

		return;

		

	var dt = new Date();

	expires = sprintf( '%d,%d,%d', dt.getUTCFullYear() + 10, dt.getUTCMonth(), dt.getUTCDate() );



	var str = 

	form.elements['PIX'].value + '^' +

	form.elements['QE'].value + '^' +

	form.elements['RN'].value + '^' +

	form.elements['GAIN'].value + '^' +

	form.elements['BIN'].value + '^' +

	form.elements['TEMP'].value + '^' +

	form.elements['TDBL'].value + '^' +

	form.elements['TREF'].value + '^' +

	form.elements['DREF'].value + '^' +

	form.elements['FL'].value + '^' +

	form.elements['DIAM'].value + '^' +

	form.elements['DIAMSEC'].value + '^' +

	form.elements['FILTER'].value + '^' +

	form.elements['EFF'].value + '^' +

	form.elements['VSTAR'].value + '^' +

	form.elements['EXPTIME'].value + '^' +

	form.elements['SEEING'].value + '^' +

	form.elements['VSKY'].value + '^' +

	form.elements['APER'].value + '^' +

	form.elements['TRANS'].value + '^';



	var sCookieName = window.location.pathname;

	_delete_cookie( sCookieName );

	_set_cookie( sCookieName, str, expires );

}



/////////////////////////////////////////////////////////////////////////

function LoadCookie()

{

	var form = document.forms['signoise'];

	if ( form == null )

		return;

	

	var sCookieName = window.location.pathname;	



	var sCookie = _get_cookie( sCookieName );

	if ( sCookie )

	{

		var ca = sCookie.split('^');

		if ( ca.length >= 20 )

		{

			form.elements['PIX'].value = ca[0];

			form.elements['QE'].value = ca[1];

			form.elements['RN'].value = ca[2];

			form.elements['GAIN'].value = ca[3];

			form.elements['BIN'].value = ca[4];

			form.elements['TEMP'].value = ca[5];

			form.elements['TDBL'].value = ca[6];

			form.elements['TREF'].value = ca[7];

			form.elements['DREF'].value = ca[8];

			form.elements['FL'].value = ca[9];

			form.elements['DIAM'].value = ca[10];

			form.elements['DIAMSEC'].value = ca[11];

			form.elements['FILTER'].value = ca[12];

			form.elements['EFF'].value = ca[13];

			form.elements['VSTAR'].value = ca[14];

			form.elements['EXPTIME'].value = ca[15];

			form.elements['SEEING'].value = ca[16];

			form.elements['VSKY'].value = ca[17];

			form.elements['APER'].value = ca[18];

			form.elements['TRANS'].value = ca[19];

			

			//window.status="Your default settings were loaded";

		}

	}

	else	// no cookie, first time initialization

	{

		form.elements['PIX'].value = 9;

		form.elements['QE'].value = 70;

		form.elements['RN'].value = 14;

		form.elements['GAIN'].value = 2.3;

		form.elements['BIN'].value = 1;

		form.elements['TEMP'].value = -10;

		form.elements['TDBL'].value = 6.3;

		form.elements['TREF'].value = 25;

		form.elements['DREF'].value = 6;

		form.elements['FL'].value = 2700;

		form.elements['DIAM'].value = 300;

		form.elements['DIAMSEC'].value = 89;

		form.elements['FILTER'].value = 'Clear';

		form.elements['EFF'].value = 90;

		form.elements['VSTAR'].value = 15;

		form.elements['EXPTIME'].value = 60;

		form.elements['SEEING'].value = 2.5;

		form.elements['VSKY'].value = 20;

		form.elements['APER'].value = 6;

		form.elements['TRANS'].value = 90;

	}

}