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Re: Scale the psf on images. [message #89970 is a reply to message #89968]

Mon, 12 January 2015 02:42

Mats Löfdahl
Messages: 263
Registered: January 2012

Senior Member

Den måndag 12 januari 2015 kl. 09:15:23 UTC+1 skrev anes.tz...@gmail.com:
> Hi
>
> I would like to perform a live test during an upcoming observing run. I want to take a series of frames on various sources and check for variability on them. I would like to make the image subtraction as accurate as possible, thus I think that image subtraction should take place after the psf of the frames is matched.
>
> Which technique you think is the best? I tried with the convolve script but the result is not good.
>
> imconv = convolve( image1, image2, FT_PSF = psf)
>
> image 1 the science frame and image is the psf frame that I created through iraf.
>
> Any suggestions are appreciated
>
> Thanks a lot.

A dirty trick you could try:

Compute the Fourier transform of both images, calculate phases and amplitudes from the real and imaginary parts of the transforms. Then substitute the amplitude in one of the images with that from the other. For the one you changed: go back to real and imaginary form, then compute the inverse transform.

The reason this might work is that the Fourier amplitude has most of the PSF information, while the phase has most of the information about the scene.

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[Message index]

		Scale the psf on images. By: anes.tziamtzis on Mon, 12 January 2015 00:15
		Re: Scale the psf on images. By: rryan%stsci.edu on Mon, 12 January 2015 01:17
		Re: Scale the psf on images. By: anes.tziamtzis on Mon, 12 January 2015 04:38
		Re: Scale the psf on images. By: anes.tziamtzis on Tue, 13 January 2015 22:50
		Re: Scale the psf on images. By: Mats Löfdahl on Wed, 14 January 2015 00:43
		Re: Scale the psf on images. By: Mats Löfdahl on Mon, 12 January 2015 02:42
		Re: Scale the psf on images. By: rryan%stsci.edu on Mon, 12 January 2015 04:57
		Re: Scale the psf on images. By: bstecklu on Tue, 13 January 2015 00:59
		Re: Scale the psf on images. By: anes.tziamtzis on Wed, 14 January 2015 23:13
		Re: Scale the psf on images. By: Mats Löfdahl on Wed, 14 January 2015 23:58
		Re: Scale the psf on images. By: anes.tziamtzis on Thu, 15 January 2015 00:04
		Re: Scale the psf on images. By: Mats Löfdahl on Thu, 15 January 2015 02:19
		Re: Scale the psf on images. By: anes.tziamtzis on Thu, 15 January 2015 05:33
		Re: Scale the psf on images. By: Mats Löfdahl on Thu, 15 January 2015 07:08
		Re: Scale the psf on images. By: Mats Löfdahl on Thu, 15 January 2015 07:12

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