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Master Flats and Masterdarks  

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(@russ-telfer)
Brown Dwarf Customer
Joined: 9 months ago
Posts: 7
March 14, 2021 13:38  

Is my understanding of Master Flats correct?

If you wish to create proper Masterflats then either Masterdarks or Bias frames have to be uploaded at the same time, (in the case of mono, for each filter channel) ?  
If so, when then calibrating and integrating the lights (at another time) do you need to load Masterdarks or do you just use the Masterflats ? 
I’ve just tried loading both masters and it gave me a calibration warning 🤔


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(@wvreeven)
Galaxy Admin
Joined: 3 years ago
Posts: 839
March 14, 2021 15:30  

@russ-telfer Hi Russell,

In order to be able to properly calibrate flats so a master flat can be created, either dark flats of the same exposure time, temperature, gain and offset are needed or darks of the same temperature, gain and offset (but a different exposure time) and bias are needed. If the dark flats have the same exposure time as the flats then bias is not needed.

However, for proper calibration of the lights, both a master flat and a master dark are needed. The master dark can be created from darks of the same exposure time, temperature, gain and offset as the lights or of darks of the same temperature, gain and offset as the lights (but different exposure time) and bias frames.

In short, bias frames are needed if for either creating the master flat or master dark or both the exposure time is different than that of the frames that get calibrated with them (which are the flats for the master flat and lights for the master dark).

The flats are used for calibrating the lights as well but once the master flat has been created, no dark flats or master dark and master bias are needed anymore. The master dark always is needed for calibrating the lights and if the exposure time of the darks is different than that of the lights then a master bias also is needed.

 

HTH, Wouter


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