The following are data product examples made from DSSI imaging
at WIYN. NESSI data is expected to be comparable.
A reconstructed image (will be in FITS format) of speckle
imaging toward a star of magnitude 10.7. This is a double source
observed in a 692nm filter. The star in the center is the "central"
science target. In this case a companion 0.55 magnitudes fainter at a
separation of 0.25 arcsec lies at a position angle 307 degrees and to
the upper right of the central star. A mirror image of the companion,
an artifact of the image reconstruction, is seen to the lower left.
Such artifacts may appear in many reconstructed speckle images.
The field of view in this image is about 2.8x2.8 arcseconds.
The background sensitivity to detecting point sources as a function of angular separation from the central star. To measure the background limit, a set of concentric annuli are defined in the reconstructed image, centered on the central star. The sky noise, defined by local minima and maxima, is measured. These are plotted as dots and plus signs respectively. The mean and standard deviation of the extrema in each annulus are found and a background limit is defined as 5 sigma brighter than the mean (with some outlier rejection of detected stars and/or artifacts). The blue squares represent the limit in each annulus and are connected by a smooth, fitted red line.
The background observed around the star centered in a 2.8x2.8 arcsecond field is sampled within a radius of ~1.4 arcseconds. The corners of the field extend to larger radii.
The background
limit in this case rises sharply from zero at the telescope
diffraction limit (~0.05 arcseconds) to 3.4 magnitudes near 0.15
arcseconds. It then rises slowly past ~4 magnitudes at larger
separations. This is a typical shape for the contrast curve.
The data table below corresponds to the background limit plotted above. The first section of the table lists the inner, outer and middle radii of the concentric annuli used to measure background noise along with the limiting magnitude. The second section of the table gives points along the fitted curve through these measurements.
# objectname: HR0 # camera: a # wavelength: 692nm # annulus range & center vs. measured relative mag. limit: 0.100000 0.200000 0.150000 3.418802 0.200000 0.250000 0.225000 3.559304 0.250000 0.350000 0.300000 3.876839 0.350000 0.450000 0.400000 4.046095 0.450000 0.550000 0.500000 4.113558 0.550000 0.650000 0.600000 4.167893 0.650000 0.750000 0.700000 4.165031 0.750000 0.850000 0.800000 4.230102 0.850000 0.950000 0.900000 4.341438 0.950000 1.050000 1.000000 4.231389 1.050000 1.150000 1.100000 4.204723 1.150000 1.250000 1.200000 4.282657 1.250000 1.350000 1.300000 4.358367 1.350000 1.450000 1.400000 4.344287 # fit of angular separation vs. relative mag. limit: 0.000000 0.000000 0.010000 0.000000 0.020000 0.000000 0.030000 0.000000 0.040000 0.000000 0.049753 0.000000 0.050000 0.008523 0.060000 0.354233 0.070000 0.699944 0.080000 1.045655 0.090000 1.391366 0.100000 1.737077 0.110000 2.082788 0.120000 2.428499 0.130000 2.774209 0.140000 3.119920 0.150000 3.465631 0.150000 3.465631 0.160000 3.483188 0.170000 3.499592 0.180000 3.515610 0.190000 3.532014 0.200000 3.549571 0.210000 3.569052 0.220000 3.591225 0.230000 3.616826 0.240000 3.645783 0.250000 3.677222 0.260000 3.710231 0.270000 3.743901 0.280000 3.777321 0.290000 3.809580 0.300000 3.839769 0.310000 3.867170 0.320000 3.891838 0.330000 3.914023 0.340000 3.933972 0.350000 3.951934 0.360000 3.968159 0.370000 3.982894 0.380000 3.996387 0.390000 4.008889 0.400000 4.020647 0.410000 4.031868 0.420000 4.042592 0.430000 4.052817 0.440000 4.062542 0.450000 4.071764 0.460000 4.080482 0.470000 4.088694 0.480000 4.096399 0.490000 4.103593 0.500000 4.110276 0.510000 4.116451 0.520000 4.122141 0.530000 4.127374 0.540000 4.132178 0.550000 4.136583 0.560000 4.140616 0.570000 4.144305 0.580000 4.147679 0.590000 4.150765 0.600000 4.153594 0.610000 4.156200 0.620000 4.158653 0.630000 4.161029 0.640000 4.163407 0.650000 4.165863 0.660000 4.168474 0.670000 4.171318 0.680000 4.174471 0.690000 4.178011 0.700000 4.182014 0.710000 4.186536 0.720000 4.191538 0.730000 4.196962 0.740000 4.202746 0.750000 4.208831 0.760000 4.215157 0.770000 4.221664 0.780000 4.228291 0.790000 4.234979 0.800000 4.241668 0.810000 4.248289 0.820000 4.254734 0.830000 4.260888 0.840000 4.266635 0.850000 4.271860 0.860000 4.276446 0.870000 4.280278 0.880000 4.283241 0.890000 4.285217 0.900000 4.286092 0.910000 4.285792 0.920000 4.284420 0.930000 4.282121 0.940000 4.279039 0.950000 4.275320 0.960000 4.271108 0.970000 4.266548 0.980000 4.261786 0.990000 4.256967 1.000000 4.252234 1.010000 4.247724 1.020000 4.243526 1.030000 4.239722 1.040000 4.236391 1.050000 4.233616 1.060000 4.231475 1.070000 4.230050 1.080000 4.229421 1.090000 4.229668 1.100000 4.230873 1.110000 4.233084 1.120000 4.236226 1.130000 4.240193 1.140000 4.244878 1.150000 4.250175 1.160000 4.255976 1.170000 4.262176 1.180000 4.268668 1.190000 4.275345 1.200000 4.282101 1.210000 4.288834 1.220000 4.295466 1.230000 4.301921 1.240000 4.308125 1.250000 4.314004 1.260000 4.319483 1.270000 4.324489 1.280000 4.328946 1.290000 4.332781 1.300000 4.335919 1.310000 4.338318 1.320000 4.340061 1.330000 4.341264 1.340000 4.342043 1.350000 4.342514 1.360000 4.342791 1.370000 4.342992 1.380000 4.343231 1.390000 4.343624 1.400000 4.344287