Why Combine Multiple Dome Flats for Master Flat Field?

In summary, multiple dome flats are combined to create a master flat field in order to reduce noise and other errors and provide a more accurate representation of the true brightness of the scene.
  • #1
the riddick25
29
0
i was given this question, and i can only guess at what the answer is. here it is

when correcting observed images, why are multiple dome flats (flat field) combined to make a master flat field?

i know how this is done, but i can't find anything to tell me why it is done.
i would presume its because this allows you to average pixel values over multiple images meaning any anomalies are discounted.



(this isn't technically homework, but if it should be moved there then sorry for any inconvenience)
 
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  • #2
It is done in order to reduce the amount of noise and other errors in the image. By combining multiple dome flats, it allows for a more accurate representation of the true brightness of the scene, as any random variations that may have been caused by noise or other factors are averaged out. This results in a much more accurate flat field which can be used to correct observed images.
 

Related to Why Combine Multiple Dome Flats for Master Flat Field?

1. Why is it necessary to combine multiple dome flats for a master flat field?

Combining multiple dome flats allows for a more accurate and precise representation of the flat field. This is because each individual flat field may have slight variations in illumination and imperfections, but when combined, these variations can be smoothed out to create a more uniform and reliable master flat field.

2. How many dome flats should be combined to create a master flat field?

The number of dome flats that should be combined depends on the specific instrument and conditions. Generally, a minimum of 10-15 dome flats is recommended for a reliable master flat field. However, if the instrument has a large field of view or if there are significant variations in illumination, more dome flats may be needed.

3. Can different exposure times be used for the dome flats when creating a master flat field?

Ideally, all dome flats should have the same exposure time to ensure consistency and accuracy in the master flat field. However, if this is not possible, it is recommended to use a range of exposure times that cover the full range of expected exposure times during observations.

4. What is the best method for combining dome flats to create a master flat field?

The most common and recommended method for combining dome flats is to take the median value of the pixel values for each pixel in the dome flats. This method helps to eliminate any outliers or variations in the flat field and produces a more uniform master flat field.

5. Do the dome flats need to be taken in the same observing conditions as the science data?

Ideally, the dome flats should be taken in the same observing conditions (e.g. telescope pointing, airmass, filters) as the science data. This helps to ensure that the master flat field accurately represents the conditions during observations. However, if this is not possible, the dome flats should at least be taken using the same instrument configuration (e.g. same filter, same camera settings) as the science data.

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