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Should I save Calibrated Images or Raw Images

msheald's picture
msheald
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Joined: 2010-10-02

Hello! I'm thinking about ways to trim my work flow. In MPO Connections, I can apply the flats and dars directly to the images as they are obtained. This would simplify my work flow and data reduction. However, it would mean that my saved images would be the calibrated images rather than the raw images I now save.

    Which is better? Saving the raw images or saving the calibrated images in case the images might need to be checked in the future? Regardless, I save the flats and dars. Best regards.

 

Mike

Well, I alway save both the
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FRF
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Joined: 2010-08-09

Well, I alway save both the raw images, flats, darks and the calibrated images as well.
You never know when do you need to recalibrate the images...

saving images
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HQA
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Joined: 2010-05-10

I save both raw and calibrated images.  Especially with AAVSOnet, we've had to go back and recalibrate images, such as when new flats were acquired and automatically applied to images, but later it was found that the flats were in error.  That said, you can actually get by with just the calibrated images and the master flat/dark/bias used for them.  All of the image operations are reversable, so if a mistake is made, you *multiply* by the flat and *add* the dark/bias, and you return to the original raw image.

However, if you have the space, I'd store both since it is easier to just apply the usual calibration steps to the original raw images than to have to recover them - fewer steps involved.  multi-terabyte hard drives are cheap today!

Arne

Should I save Calibrated images or Raw Images
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FJQ
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Joined: 2010-07-25

To:  Arne,

Thanks for your insight.  How long do you think we should store these data?  I have one directory ( 1 each for the different SBIG cameras I've used) with my daily data.  When the variable is lost in the evenning twilight or behind my 2-story house, I do a search on this individual variable and extract 4-6 months of data.  I copy this to another directory that is in a folder with the variable star and name reduce these 4-6 months images with MaximDL's photometric function in the extended AASVO fomat for submission to WEBobs.

My question, how long should I keep this CCD image data (raw/calibrated/sorted) after its been uploaded to AASVO? Is 6 months good, 12 months, 2 years, etc?

James

 

archival duration
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HQA
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Joined: 2010-05-10

Hi James,

The answer is: forever.  I have images from 1984 that are still useful, and go back to images in the 1990's quite often.  I *do* extract all stars from all images, but sometimes I want to stack them differently for a specific project, or look at extended nebulosity, or see if a reported faint companion is present, especially on the best seeing nights.  With the cost of storage today, I see no reason to throw away images.

Arne

Calibrated or Raw Images?
msheald's picture
msheald
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Joined: 2010-10-02

Hello! Thanks everyone for your comments. Best regards.

Mike

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484