Preparing an UCLES Proposal
Signal to Noise Calculator
Please use the UCLES Signal to Noise calculator to estimate the exposure time for your observing program.
Gratings
UCLES provide high resolution as set by the slit width. The spectral resolution is measured as Lambda / delta_Lambda, where delta_Lambda = FWHM of unresolved lines (usually 2 pixels). Rmax ~ 100,000, and a typical 1 arcsec slit width corresponds to R ~ 45,000.
The wavelength coverage is set by the choice of grating, where the 31/6 lines/mm grating gives almost continuous wavelength coverage at the bluer wavelengths with a shorter slit length, while the 79 lines/mm grating gives 2.5 times longer slit but less complete wavelength coverage. Both gratings produce almost identical dispersion and resolution, and the primary difference is in the free spectral range and order separation.
Detector (Please note that the MITLL detector has been decommissioned as of semester 2016B)
1. Blue sensitive E2V 2K x 4K (13.5 micron pixels)
Image scale: 0.16 arcsec per spatial pixel
On chip binning in both spatial and spectral direction is possible.
| SPEED | READ OUT TIME (s) | GAIN (e-/ADU) | READ OUT NOISE (e-) | SATURATION (e-) | NON-LINEARITY (ALPHA x10-6) |
|---|---|---|---|---|---|
| SLOW | 445 (403) | 0.37 | 2.45 (2.3) | 24,000 (ADC) | 0.14 |
| NORMAL | 178 (158) | 1.30 | 3.15 (3.2) | 85,000 (ADC) | 0.60 |
| FAST | 132 (132) | 2.80 | 5.27 (5.35) | 183,000 (ADC) | 0.78 |
| NONASTRO | 89 (74) | 6.67 | 9.74 (9.8) | 437,000 (ADC) | 1.92 |
2. Red sensitive MITLL3 2K x 4K (15 micron pixels) - Please note that the MITLL detector has been decommissioned as of semester 2016B, this is kept here for legacy reasons
Image scale: 0.18 arcsec per spatial pixel
No binning possible.
| SPEED | READ OUT TIME (s) | GAIN (e-/ADU) | READ OUT NOISE (e-) | SATURATION (e-) | NON-LINEARITY (ALPHA x10-6) |
|---|---|---|---|---|---|
| XTRASLOW | (936) | 0.074 | (1.16) | 5,000 (ADC) | -0.23 |
| SLOW | 300 (296) | 0.37 | 1.84 (1.7) | 24,000 (ADC) | 0.23 |
| NORMAL | 163 (154) | 1.1 | 2.38 (2.4) | 72,000 (ADC) | 0.36 |
| FAST | 127 (120) | 2.2 | 3.47 (3.3) | 141,000 (ADC) | 0.19 |
| NONASTRO | 85 (75) | 4.5 | 6.55 (6.3) | 178,000 | 0.02 |
Notes:
READOUT TIME: Lab measurements are given in parentheses.
READOUT NOISE: Lab measurements are given in parentheses.
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