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Stacking RAW images in IRIS

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Chris Allen

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Joined: 04/05/2010

Posts: 10

Teams: DSLR Documentation and Reduction

Posted: July 17, 2010 - 8:58am

Firstly, many thanks to all who replied to my previous posting about the bias frames.

I have two further questions about IRIS.

(1) On my Canon 50D DSLR, it is possible to reduce noise reduction for long exposure photographs. I heard somewhere that this involves the camera substracting a dark frame automatically, to reduce noise with 'bulb' exposures. Does this mean that beginners could possibly skip the dark frame step? Comments welcome.

(2) I wonder how you stack and align images in IRIS. I took 5 RAW images of beta Lyr last night. How do I stack and align these images in IRIS (can't find the help file).

Many thanks in advance

Chris Allen / Sweden

robin_astro

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Joined: 06/16/2009

Posts: 99

Teams: None

Posted: July 17, 2010 - 10:04am

Hi Chris, You can find a tutorial covering the full sequence of processing steps for DSLRimages in IRISincluding aligning and stacking here on Christian Buil's website http://www.astrosurf.com/buil/iris/tutorial3/doc13_us.htm Note For scientific work is it important not to make anychanges to the imagewhich alter the data in the image so do not process the image any furtherbeyond the stackingstep. There are also several other tutorials for various procedures using IRISlinked from the IRISdowloadpage here http://www.astrosurf.com/buil/us/iris/iris.htm Alternatively you could measure the magnitudes on the individual images and average the results (more useful in my view as it also gives you an estimate of your variability and thereforean estimate of the precision) Robin