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Flat settings

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#1 DSO_Viewer

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Posted 23 April 2019 - 02:46 PM

When doing my flats with a cmos ZWO camera do I have to set my offset, gain, and temperature the same as my lights? Thank you.

 

Steve



#2 NMCN

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Posted 23 April 2019 - 04:25 PM

When doing my flats with a cmos ZWO camera do I have to set my offset, gain, and temperature the same as my lights? Thank you.

 

Steve

 

I believe its best practice to do that, so that's how I take them.


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#3 pkrallis

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Posted 23 April 2019 - 04:32 PM

As with most scientific undertakings the fewer things that are changed in each step of the process the easier it is to determine the effect of changes.  Mariner 2 has it right.



#4 jdupton

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Posted 23 April 2019 - 05:13 PM

Steve,

 

   As indicated above, it is best practice to do everything at the same gain, offset, and sensor temperature. Use exactly the same settings for lights, darks, flats, and flat-darks. That will give you the best calibration results.

 

   Technically speaking, you could use different settings for your flats if and only if your flat-darks match the flats exactly in terms of gain, offset, and temperature. This is because once the flat is itself calibrated with its matching flat-dark, it is applied in a ratio-metric manner to the lights during calibration. You will be doing a division based operation using the ratio of the flat to the mean of the flat when it is applied to the light. A ratio is a unit-less quantity so the original units don't come into the equation.

 

   Again, it is usually easier to shoot everything at the same settings. It also reduces the chances for introducing errors if you are not careful in the flat calibration stage.

 

 

John



#5 DSO_Viewer

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Posted 23 April 2019 - 06:03 PM

Steve,

 

   As indicated above, it is best practice to do everything at the same gain, offset, and sensor temperature. Use exactly the same settings for lights, darks, flats, and flat-darks. That will give you the best calibration results.

 

   Technically speaking, you could use different settings for your flats if and only if your flat-darks match the flats exactly in terms of gain, offset, and temperature. This is because once the flat is itself calibrated with its matching flat-dark, it is applied in a ratio-metric manner to the lights during calibration. You will be doing a division based operation using the ratio of the flat to the mean of the flat when it is applied to the light. A ratio is a unit-less quantity so the original units don't come into the equation.

 

   Again, it is usually easier to shoot everything at the same settings. It also reduces the chances for introducing errors if you are not careful in the flat calibration stage.

 

 

John

Thank you very much gentleman for the helpful information and I will follow what you all suggested.

 

Steve




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