ao:slow_wfs
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ao:slow_wfs [2018/07/06 13:37] 127.0.0.1 external edit |
ao:slow_wfs [2018/07/08 10:50] (current) jones |
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| + | ====== Slow WFS ====== | ||
| ==== Basic Principles ==== | ==== Basic Principles ==== | ||
| \\ The slow wavefront sensor, if used with starlight, could have the following functions: | \\ The slow wavefront sensor, if used with starlight, could have the following functions: | ||
| Line 48: | Line 49: | ||
| * Pupil location is fed back to the BRT secondary, M12 or M10 (see B above). | * Pupil location is fed back to the BRT secondary, M12 or M10 (see B above). | ||
| \\ | \\ | ||
| - | ==== **Flux Requirement for AO Lock for Calibration** ==== | + | ==== Flux Requirement for AO Lock for Calibration ==== |
| \\ In order to get good sky coverage of reference stars, we will assume that the AO calibration is done on a 4th magnitude A star. Assuming B-band and half of V-band (0.4 to 0.55 microns), 80,000 photons arrive at the top of the atmosphere in every 5 millsec for a 0.2 m aperture. Assuming that we need at least 100 photons for a lock, this puts a minimum system throughput requirement of 0.13%. With a CHARA throughput in the blue of about 2% and 65% WFS quantum efficiency, this means that an IR dichroic throughput of at least 10% is needed over the 0.4 to 0.55 micron band in order to lock the slow WFS on calibration stars.\\ \\ | \\ In order to get good sky coverage of reference stars, we will assume that the AO calibration is done on a 4th magnitude A star. Assuming B-band and half of V-band (0.4 to 0.55 microns), 80,000 photons arrive at the top of the atmosphere in every 5 millsec for a 0.2 m aperture. Assuming that we need at least 100 photons for a lock, this puts a minimum system throughput requirement of 0.13%. With a CHARA throughput in the blue of about 2% and 65% WFS quantum efficiency, this means that an IR dichroic throughput of at least 10% is needed over the 0.4 to 0.55 micron band in order to lock the slow WFS on calibration stars.\\ \\ | ||
| ==== Flux Requirement for Slow WFS Lock (starlight-only operation) ==== | ==== Flux Requirement for Slow WFS Lock (starlight-only operation) ==== | ||
ao/slow_wfs.1530898654.txt.gz ยท Last modified: 2018/07/06 13:37 by 127.0.0.1
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