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DanielVanNoord / open-phd-guiding

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Help file: add documentation for Auto exposure #288

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
The Auto exposure feature needs to be documented in the help file.

Original issue reported on code.google.com by andy.gal...@gmail.com on 22 May 2014 at 3:29

GoogleCodeExporter commented 9 years ago 
The camera exposure drop-down list in the main window has a new entry, Auto. 
When exposure is set to Auto, PHD2 will attempt to adjust the exposure to keep 
the selected guide star at a constant SNR value. The Auto setting can be 
especially beneficial for AO users who want to minimize exposure time without 
losing the guide star.

On the Global tab in the Advanced dialog, there is a group of settings to 
control auto-exposure.

  Min Exposure: the minimum exposure time. PHD2 will not set the exposure time less than this value, even if the guide star SNR is higher than the target SNR value. If the min exposure time is set too low, you could end up sending excessive small corrections to the mount which may not give the best guiding results. Users with AO units would want to set this to a lower value, since rapid small corrections are often desirable with an AO.
  Max Exposure: the maximum exposure time. Before a guide star is selected, PHD2 will set the exposure time to the maximum value. Once a guide star is selected, PHD2 will then incrementally decrease the exposure time until the desired SNR is reached.
  Target SNR: this is the average SNR value that PHD2 will attempt to achieve by adjusting the exposure time. SNR can fluctuate from frame to frame even with a fixed exposure duration, so be sure to account for that when choosing a target SNR value. PHD2 will reject frames when SNR drops below 3.0. The default value of 6.0 should provide enough of a buffer to prevent fluctuations from causing the SNR to go below 3.0.

Original comment by andy.gal...@gmail.com on 22 May 2014 at 4:18

GoogleCodeExporter commented 9 years ago 
This issue was closed by revision r866.

Original comment by andy.gal...@gmail.com on 28 May 2014 at 5:23