Coudé Gratings

The gratings available with the coude spectrograph include the four conventional coude gratings (A, B, C, and D), the echelle grating, and the full set of gratings from the 4m RC Spectrograph. The echelle grating can be used with grisms from the 4m Cryogenic Camera to provide cross dispersion, and the echelle grating gives resolutions of approximately 100,000 on Camera 5 and 250,000 on Camera 6. The RC gratings are used for lower resolution work with wide spectral coverage.
Designation              A            B           C            D
Ruled Area (mm)       304x361      309x370     204x254      204x308
Grooves/mm              632          316         600         1200
Blaze (A), 1st Order   12000        12000        8000        8000
Blaze Angle...          22.3         11.         13.9        28.8
ghost intensity (%)    0.005        0.002        0.06         0.1



	 Grooves   Blaze (A)    Dispersion (A/mm)
Grating  per mm    1st Order    Cam. 5    Cam. 6

RC-250     158      4000         60         17
RC-400     158	    8000         60         17
KPC-10A    316      4000         30	    8.4
RC-181     316      7500         30         8.4
KPC-7      632	    5200         15         4.2
RC-450     632     11000         15	    4.2
KPC-17     527      5540         18         5.3
KPC-18     790	    8500         12         3.3
Only cameras 5 and 6 are available with CCD detectors. Cameras 2 and 3 are available with photographic plates only, and are generally not used.

			     Camera 5            Camera 6
			 ---------------------------------------
		Grating    blue      red    I    blue      red
----------------------------------------------------------------
reciprocal         A       4.7      7.0          1.4       2.1
dispersion         B       9.9     14.8          2.8       4.2
(A/mm)             C       7.8     15.7          2.2       4.4
		   D       3.8      7.6          1.1       2.2
		  ECH	   1.2      1.8          0.32      0.51
----------------------------------------------------------------
resolution(A)      A       0.14     0.21         0.04      0.06
(for 2 pixel       B       0.30     0.44         0.08      0.12
 line width,       C       0.23     0.47         0.06      0.13
TI CCD,0.015       D       0.12     0.23         0.04      0.06
 mm pixels $)     ECH      0.035    0.055        0.0096    0.015
----------------------------------------------------------------
spectral           A      56       84           16        25
coverage (A)       B     118      177           34        50
TI CCD		   C      94      188           26        52
(800 pixels #)     D	  45       91           12        26
		  ECH     14.0     22.0          3.84      6.0
----------------------------------------------------------------
exposure time      A     450      300        *1500     *1000
(sec) for          B     200      150         *600      *300
 S/N=100           C     300      400         *900      *400
 (feed tel)        D     500      300        *2000     *1000
 (V=6.0) ECH   1800      900
----------------------------------------------------------------
*Using on-chip pixel summation perpendicular to dispersion.
$Multiply by: 1.4 - S2KA; 1.6 - T1KA,T2KA(B); 1.8 - TEK2
#Multiply by: 3.58 - S2KA; 2.05 - T1KA, 4.10 - T2KA(B);
	      1.15 - TEK2, 3.87 - FO3K