8.3.5 Pertinent Spectrograph Parameters

  Table 8.7 contains further spectrographic lay-out and design information which has bearing on spectroscopic behavior for the three IUE cameras. The echelle grating and cross-disperser parameters are taken from Boggess et al. (1978), Evans (1975), and the IUE System Design Report (1976). These values are believed to be accurate, except that there is evidence that the effective focal lengths of the cameras were modified by several percent during the instrument assembly and testing stages.

 

 

Parameter LWP LWR SWP

Wavelength Range (Å) 1808-3359 1810-3456 1097-2097

Order Range 69-127 67-127 66-125

Abs. Calib. Wavelength Range (Å) 1850-3350 1850-3350 1150-1980

Abs. Calib. Order Range 69-125 69-125 70-120

Coll. Focal Length (mm) 950 950 950

Cam. Focal Length (mm) 684 684 684

Coll.-to-Cam. Angle (deg.) 20.42 20.42 20.37

$$\mu$$ 36.4 36.4 35.7

X-Disp. Ruling Freq. (gr mm^-1) 241.50 241.50 369.233

X-Disp. Order 1 1 1

Ech. Ruling Freq. (gr mm^-1) 63.207 63.207 101.947

$$\mu$$ 23.19 23.19 13.76

$$\beta$$ 48.126 48.126 45.449

$$\phi$$

The approximate wavelength ranges for each order are listed in Table 8.8. These values will vary by several tenths of an Å ngstrom due to the global shifts in the location of the spectral format as a function of time and THDA.

 

 

Order LWP LWR SWP

No. Large Small Large Small Large Small

127 1808.9-1830.6 1809.9-1831.9 1811.6-1830.5 1811.5-1831.7

126 1823.1-1845.2 1824.0-1846.7 1824.4-1845.4 1825.6-1846.7

125 1850.0-1860.2 1850.0-1861.3 1850.2-1860.4 1850.0-1861.8 1098.1-1112.6 1097.3-1112.0

124 1852.0-1875.1 1853.1-1876.9 1853.3-1875.8 1854.5-1877.1 1106.8-1121.6 1106.0-1121.0

123 1866.8-1891.0 1867.9-1892.4 1868.3-1891.2 1869.3-1892.6 1115.7-1130.9 1114.9-1130.3

122 1881.9-1906.7 1883.0-1908.0 1883.2-1906.9 1884.4-1908.9 1124.7-1140.3 1123.9-1139.7

121 1897.3-1922.7 1898.3-1924.0 1900.0-1923.0 1901.2-1924.3 1133.8-1149.8 1133.1-1149.2

120 1912.8-1938.9 1913.9-1940.3 1915.8-1939.2 1915.4-1940.5 1150.0-1157.8 1150.0-1158.0

119 1928.7-1955.4 1929.7-1956.8 1930.0-1955.5 1931.3-1957.1 1152.6-1167.6 1151.7-1167.7

118 1944.7-1972.2 1946.3-1973.5 1946.2-1972.6 1947.4-1974.0 1162.2-1177.6 1161.4-1177.7

117 1961.7-1989.2 1962.3-1990.6 1962.6-1989.6 1963.9-1991.0 1172.0-1187.7 1171.2-1187.8

116 1977.9-2006.6 1979.1-2008.0 1979.3-2007.0 1980.6-2008.4 1181.9-1197.8 1181.2-1198.1

115 1994.9-2024.2 1996.1-2025.6 1996.3-2023.9 1997.6-2026.1 1192.0-1208.5 1191.3-1208.6

114 2012.2-2042.1 2013.4-2043.5 2015.0-2041.7 2016.1-2044.0 1202.3-1219.1 1201.6-1219.2

113 2029.8-2060.4 2031.0-2061.8 2032.8-2060.8 2032.6-2062.2 1213.7-1230.1 1212.1-1230.1

112 2047.7-2079.0 2049.0-2080.4 2049.2-2079.4 2050.5-2080.9 1224.5-1241.0 1222.8-1241.1

111 2065.0-2097.9 2067.3-2099.3 2067.5-2098.4 2068.8-2099.8 1234.5-1252.3 1233.7-1252.4

110 2084.7-2117.1 2085.9-2118.5 2086.1-2117.6 2087.5-2119.1 1245.6-1263.7 1244.8-1263.8

109 2103.6-2136.7 2104.8-2138.1 2105.1-2137.2 2106.4-2138.7 1256.9-1275.4 1256.1-1275.5

108 2122.9-2155.5 2124.2-2156.7 2124.4-2157.2 2126.7-2158.8 1268.4-1287.3 1267.6-1287.4

107 2142.6-2175.6 2143.9-2178.3 2145.2-2177.5 2146.4-2179.0 1280.1-1299.4 1279.8-1299.5

106 2162.4-2197.6 2163.9-2198.9 2164.2-2198.2 2165.6-2199.7 1292.7-1311.7 1291.3-1311.8

105 2183.0-2218.7 2184.4-2220.0 2184.6-2219.4 2186.0-2220.6 1304.3-1323.6 1303.5-1324.4

104 2203.9-2239.9 2205.2-2241.5 2205.5-2240.9 2206.9-2242.3 1316.7-1337.1 1316.0-1337.2

103 2225.2-2261.8 2226.6-2263.5 2226.7-2262.8 2228.2-2264.2 1329.4-1350.2 1328.7-1350.3

102 2246.9-2284.0 2248.1-2285.4 2248.4-2285.1 2249.9-2286.6 1342.4-1363.5 1341.6-1363.6

101 2269.0-2306.6 2270.4-2308.0 2270.6-2307.5 2272.0-2309.0 1355.6-1377.1 1354.8-1376.8

100 2291.4-2329.8 2292.9-2331.3 2293.2-2330.6 2294.7-2332.6 1369.1-1391.0 1368.3-1391.1

99 2314.5-2353.4 2316.0-2353.2 2316.2-2353.5 2317.7-2355.0 1382.8-1405.0 1382.0-1405.3

98 2338.0-2375.6 2339.4-2379.0 2339.7-2378.9 2341.8-2380.5 1396.9-1418.9 1396.1-1419.7

97 2362.0-2402.1 2363.4-2403.7 2363.9-2403.5 2365.4-2405.1 1411.2-1434.3 1410.4-1434.4

96 2387.0-2427.2 2388.5-2428.7 2388.3-2428.6 2389.9-2430.3 1425.8-1449.4 1425.0-1449.5

95 2411.5-2452.7 2412.9-2454.3 2413.6-2454.3 2415.1-2455.9 1440.8-1463.2 1440.0-1464.9

94 2437.2-2478.8 2438.7-2480.4 2439.0-2480.5 2440.6-2482.1 1456.1-1480.5 1455.3-1480.6

93 2463.4-2505.4 2464.9-2507.0 2466.7-2507.2 2466.9-2508.3 1471.7-1496.5 1470.9-1496.6

92 2490.0-2532.6 2491.6-2534.2 2492.0-2533.6 2493.6-2536.0 1488.3-1512.7 1487.5-1511.9

91 2517.3-2560.5 2518.9-2560.5 2519.3-2562.2 2521.0-2563.5 1504.0-1529.7 1503.2-1529.8

90 2545.4-2588.8 2547.0-2590.4 2547.4-2590.5 2549.1-2592.3 1520.7-1546.8 1519.9-1546.9

89 2574.1-2617.8 2576.6-2619.4 2576.0-2619.8 2577.7-2621.4 1537.8-1564.4 1536.9-1564.5

88 2604.3-2647.4 2605.0-2649.0 2605.4-2649.5 2607.1-2651.2 1555.3-1582.3 1554.4-1582.4

87 2633.5-2677.7 2635.1-2679.3 2635.4-2680.0 2637.1-2681.5 1573.2-1600.6 1572.3-1600.8

86 2664.2-2708.6 2666.0-2710.2 2668.3-2711.0 2669.8-2712.6 1591.6-1619.4 1590.7-1619.5

85 2695.7-2740.6 2697.5-2742.0 2697.8-2742.9 2699.5-2744.5 1610.4-1638.6 1610.6-1636.7

84 2727.9-2772.5 2729.8-2774.1 2731.8-2775.3 2733.5-2777.0 1630.4-1657.0 1628.7-1658.0

83 2761.1-2805.8 2762.9-2807.5 2763.2-2808.4 2765.0-2810.2 1649.3-1678.5 1648.4-1677.8

82 2795.5-2839.3 2797.3-2841.3 2797.3-2842.3 2799.1-2843.0 1669.6-1699.0 1668.6-1669.5

81 2830.1-2874.2 2831.9-2875.9 2832.0-2877.3 2833.9-2879.1 1690.5-1719.8 1689.6-1718.9

80 2865.8-2909.7 2867.7-2911.3 2869.1-2912.9 2870.9-2914.6 1711.8-1741.2 1710.9-1740.3

79 2902.6-2946.0 2904.5-2947.6 2904.5-2949.2 2906.4-2950.7 1733.7-1763.0 1732.8-1762.0

78 2940.3-2982.9 2942.3-2984.6 2942.2-2986.3 2944.1-2988.0 1756.4-1784.9 1755.4-1784.3

77 2979.2-3020.7 2981.3-3022.3 2980.9-3024.6 2982.9-3026.5 1779.3-1808.2 1778.3-1807.1

76 3019.2-3059.5 3021.3-3061.2 3020.9-3063.6 3022.8-3065.4 1803.0-1831.6 1803.5-1830.5

75 3060.3-3099.4 3062.6-3101.2 3061.9-3103.7 3066.4-3105.7 1827.4-1854.6 1826.5-1853.7

74 3102.5-3140.3 3105.0-3142.1 3104.3-3144.9 3106.8-3146.8 1852.6-1880.2 1851.7-1879.2

73 3146.7-3182.0 3148.9-3183.4 3148.8-3187.4 3150.6-3189.3 1878.5-1905.4 1877.6-1904.2

72 3191.9-3224.6 3194.2-3225.5 3193.0-3230.0 3195.3-3232.1 1905.3-1931.2 1904.4-1930.0

71 3237.4-3267.0 3239.5-3268.9 3240.8-3273.4 3242.8-3275.8 1932.9-1957.7 1931.9-1956.5

70 3287.8-3311.7 3290.2-3312.6 3287.9-3318.3 3290.2-3320.4 1961.5-1980.0 1960.5-1980.0

69 3338.8-3348.2 3342.2-3349.9 3338.3-3350.0 3340.7-3349.9 1990.9-2012.4 1989.9-2011.2

68 3390.7-3410.0 3393.5-3411.4 2021.5-2040.7 2020.6-2039.3

67 3444.3-3456.5 3446.5-3458.7 2053.5-2069.2 2052.6-2067.6

66 2087.4-2097.7 2086.3-2096.1

A few remarks concerning the spectrographic elements:

• the collimator mirror is an off-axis paraboloid,
• the camera mirror is ruled as the cross-dispersing element,
• the echelle grating operates in a Littrow mode,
• the separation of the incoming and outgoing rays at the grating is achieved in the direction perpendicular to the dispersion (i.e, the echelle operates in an ``over-under Littrow mode''),
• differences in the dispersion caused by the angular separation between the large and small entrance apertures are <0.1% and are not detectable.

Note finally that the wavelength coverage for the long wavelength cameras, particularly for the LWR, extends into the accessible range of ground-based instruments. The long-wavelength limits for absolutely calibrated fluxes for all three cameras is limited by the low-dispersion spectra impinging on the camera target ring.