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Re: Coadd images that contain no stars [message #80329 is a reply to message #80328]

Sun, 27 May 2012 08:15

spasoklampanas
Messages: 8
Registered: May 2012

Junior Member

On May 27, 6:05 pm, Russell Ryan <rr...@stsci.edu> wrote:
> On May 27, 10:56 am, spasoklampa...@yahoo.com wrote:
>
>> Hi,
>
>> I have two images from GALEX from a molecular cloud, that need to
>> be combined to create an image. The problem is that there are no stars
>> present. There is only the nebula. How is it possible to coadd these
>> two frames? On each image half of the cloud is present and there is
>> some overlap of course. Is there a way in IDL?
>
>> Thanks a lot
>
> Why cant you just add them? I'm confused....
>
> Do you need to align the images? If so, then you need to correlate
> the two images to find the appropriate shifts. Even then, and I know
> how careful you need to be, the GALEX PSF varies across the FoV
> significantly. So coadding frames of anything can be very tricky if
> they're not centered on precisely the same position in the sky.

In the first frame half of the cloud is seen in the lower left part of
the frame, while in the second frame the other is seen in the upper
right part of the image. So i need to create a single frame of the
cloud by adding them. The resolution is not my priority, since the
resolution will be degraded it to match frames with a pixel scale of
one arcminute. The problem is how i can estimate the dithering when
there are no stars?

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[Message index]

		Re: Coadd images that contain no stars By: Mats Löfdahl on Wed, 30 May 2012 06:03
		Re: Coadd images that contain no stars By: Helder Marchetto on Wed, 30 May 2012 04:53
		Re: Coadd images that contain no stars By: Mats Löfdahl on Wed, 30 May 2012 04:17
		Re: Coadd images that contain no stars By: Helder Marchetto on Wed, 30 May 2012 01:58
		Re: Coadd images that contain no stars By: Russell Ryan on Sun, 27 May 2012 22:26
		Re: Coadd images that contain no stars By: spasoklampanas on Sun, 27 May 2012 08:19
		Re: Coadd images that contain no stars By: spasoklampanas on Sun, 27 May 2012 08:15
		Re: Coadd images that contain no stars By: Russell Ryan on Sun, 27 May 2012 08:05

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