combining multiple exposures of one filter

puchao wrote on Sep 05, 2008

Using the NICMOS camera, I have gathered multiple exposures for one filter with different exposure times and I would like to combine the resulting images using iraf.

Thanks.

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Francisco Valdes wrote on Sep 05, 2008

The basic task used to combine images is IMCOMBINE. There are some variants. These work if the images are registered in pixel space. If they need to be registered before adding it becomes more complicated. STScI has create some task to optimally handle combining data with slight shifts. Handling different exposure times is generally a matter of scaling and weighting. Of course an even simpler method is to add the exposures with something like IMCOMBINE or IMSUM. When adding the questions of scaling and weighting are dealt with naturally (assuming the data has been properly bias and flat field calibrated).

I suggest you send your question to help@stsci.edu for the recommended way to do what you want.

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Last post on Sep 05, 2008