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Grating Spectrograph Designer

Units and System Parameters
Hide Description Value Hide Description Value
Unit of Distance Unit of Angle At Object
Unit of Wavelength Central Wavelength [micron]
System Imaging Focal Length [m]

Object Parameters
Hide Description Value Hide Description Value
Slit Length at Object [rad] Diffraction Limit at Object [rad]

Telescope Parameters
Hide Description Value Hide Description Value
Telescope Pupil Diameter [m] Telescope Focal Length [m]
Telescope Focal Ratio Telescope Plate Scale [rad/m]
Slit Length at Telescope Focus [m] Diffraction Limit at Telescope [m]

Slit Parameters
Hide Description Value Hide Description Value
Slit Width at Object [rad] Slit Width at Telescope Focus [m]
Projected Slit Width [pixel]

Collimator Parameters
Hide Description Value Hide Description Value
Collimator Focal Length [m] Collimator Beam Size [m]

Grating Parameters
Hide Description Value Hide Description Value
Grating Groove Pitch [line/mm] Grating Order
Grating Input Angle (alpha) [deg] Grating Spectrograph Angle [deg]
Grating Beam Ratio Grating Length [m]
Grating Free Spectral Range [micron] Grating Free Spectral Range [pixel]
Grating Dispersion [micron/pixel] Grating Dispersion [m/s/pixel]
Grating Dispersion [R-pixel] Grating Dispersion [micron/slit]
Grating Dispersion [m/s/slit] Grating Dispersion [R-slit]

Camera Parameters
Hide Description Value Hide Description Value
Camera Focal Length [m] Camera Imaging Focal Ratio
Camera Half-Width [deg]

Detector Parameters
Hide Description Value Hide Description Value
Detector Pixel Size [micron] System Imaging Plate Scale [pixel/rad]
Detector Width [pixel]

Diffraction parameters
Hide Description Value Hide Description Value
Diffraction Limit (cross-disp) [pixel] Diffraction Limit (disp-dir) [pixel]

Secondary Wavelengths
Hide Description Value Hide Description Value
Lo Wavelength [micron] Hi Wavelength [micron] 


	    
	    
	    
	


	


	
		
	    
Instructions:

	    
    
	    
  •  This web page is a multi-directional spreadsheet.  All the cells are interlinked, so setting one cell might change any other cell. 
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  •  The "enter" key or the  button will fill in the derivable values. 
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  •  Checking the  "Hide" boxes will make the variable not show. 
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  •   will show all variables, even internal variables of no interest. 
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  •   will set the variables back to the values since the last . 
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  •  For earlier values, use the browser's  button. 
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  •  The spreadsheet silently ignores non-numeric or invalid input. 
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    If the values come up in red, then there is some problem, which is usually the fault of the user.  The most likely causes are:
    
    
        
  •  A set of variables was picked that is overdetermined. Using "enter" after every entry will prevent this. 
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  •  The input values do not correspond to a physically realizable system. 
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  •  Some unusual branch-cut was encountered, not already known to the program. 
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  •  The program does not know how to take limits, so values close to lim{ (x→0)/(y→0) } will be incorrect. 
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  •  Sometimes the grating angles are 180 degrees off.  Not sure why this happens. 
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    Also, some capabilities of the underlying program are not implemented by the web interface.
    Mainly, this is when "LOOP" appears, which means that a ring of variables exist which could
    in theory be solved, but the program needs to be given a starting value.



    
To-do list:

    
    
        
  •  There are cases where a variable could be dropped out of the equations, but the program does not know to do so. 
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  •  Change to column-down ordering, rather than side-by-side 
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  •  Initial values for LOOP's 
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  •  Add Javascript to check validity of input values 
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  •  Grism and prism versions 
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The code for this tool has not been touched since 2007. Expect some amount of bitrot.